AMEREN ILLINOIS CO, 10-K filed on 2/26/2016
Annual Report
Document And Entity Information (USD $)
12 Months Ended
Dec. 31, 2015
Jan. 29, 2016
Jun. 30, 2015
Document Type
10-K 
 
 
Amendment Flag
false 
 
 
Document Period End Date
Dec. 31, 2015 
 
 
Document Fiscal Year Focus
2015 
 
 
Document Fiscal Period Focus
FY 
 
 
Trading Symbol
AEE 
 
 
Entity Registrant Name
AMEREN CORP 
 
 
Entity Central Index Key
0001002910 
 
 
Current Fiscal Year End Date
--12-31 
 
 
Entity Filer Category
Large Accelerated Filer 
 
 
Entity Common Stock, Shares Outstanding
 
242,634,798 
 
Entity Voluntary Filers
No 
 
 
Entity Current Reporting Status
Yes 
 
 
Entity Public Float
 
 
$ 9,142,479,189 
Entity Well-known Seasoned Issuer
Yes 
 
 
Union Electric Company
 
 
 
Document Type
10-K 
 
 
Amendment Flag
false 
 
 
Document Period End Date
Dec. 31, 2015 
 
 
Document Fiscal Year Focus
2015 
 
 
Document Fiscal Period Focus
FY 
 
 
Trading Symbol
AEE 
 
 
Entity Registrant Name
UNION ELECTRIC CO 
 
 
Entity Central Index Key
0000100826 
 
 
Current Fiscal Year End Date
--12-31 
 
 
Entity Filer Category
Non-accelerated Filer 
 
 
Entity Common Stock, Shares Outstanding
 
102,123,834 
 
Entity Voluntary Filers
No 
 
 
Entity Current Reporting Status
Yes 
 
 
Entity Well-known Seasoned Issuer
No 
 
 
Ameren Illinois Company
 
 
 
Document Type
10-K 
 
 
Amendment Flag
false 
 
 
Document Period End Date
Dec. 31, 2015 
 
 
Document Fiscal Year Focus
2015 
 
 
Document Fiscal Period Focus
FY 
 
 
Trading Symbol
AEE 
 
 
Entity Registrant Name
Ameren Illinois Co 
 
 
Entity Central Index Key
0000018654 
 
 
Current Fiscal Year End Date
--12-31 
 
 
Entity Filer Category
Non-accelerated Filer 
 
 
Entity Common Stock, Shares Outstanding
 
25,452,373 
 
Entity Voluntary Filers
No 
 
 
Entity Current Reporting Status
Yes 
 
 
Entity Well-known Seasoned Issuer
Yes 
 
 
Consolidated Statement Of Income (Loss) (USD $)
In Millions, except Per Share data, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Operating Revenues:
 
 
 
Electric
$ 5,180 
$ 4,913 
$ 4,832 
Gas
918 
1,140 
1,006 
Total operating revenues
6,098 
6,053 
5,838 
Operating Expenses:
 
 
 
Fuel
878 
826 
845 
Purchased power
514 
461 
508 
Gas purchased for resale
415 
615 
526 
Other operations and maintenance
1,694 
1,684 
1,611 
Provision for Callaway construction and operating license
69 
 
0 
Depreciation and amortization
796 
745 
706 
Taxes other than income taxes
473 
468 
458 
Total operating expenses
4,839 
4,799 
4,654 
Operating Income
1,259 
1,254 
1,184 
Other Income and Expenses:
 
 
 
Miscellaneous income
74 1
79 1
69 1
Miscellaneous expense
30 1
22 1
26 1
Total other income (expense)
44 
57 
43 
Interest charges
355 
341 
398 
Income Before Income Taxes
948 
970 
829 
Income taxes
363 
377 
311 
Income from Continuing Operations
585 
593 
518 
Income (Loss) from Discontinued Operations, Net of Tax (Note 16)
51 
(1)
(223)
Net Income (Loss)
636 
592 
295 
Pension and other postretirement activity, net of income taxes (benefit)
6 
(12)
30 
Comprehensive Income (Loss)
636 
574 
300 
Less: Net Income (Loss) Attributable to Noncontrolling Interests:
 
 
 
Continuing Operations
6 
6 
6 
Net Income (Loss):
 
 
 
Net income attributable to Ameren Corporation - continuing operations
579 
587 
512 
Discontinued Operations
51 
(1)
(223)
Net income (loss) attributable to Ameren Corporation
630 
586 
289 
Earnings (Loss) per Common Share – Basic:
 
 
 
Continuing Operations - Basic
$ 2.39 
$ 2.42 
$ 2.11 
Discontinued Operations - Basic
$ 0.21 
$ 0.00 
$ (0.92)
Earnings (Loss) per Common Share – Basic
$ 2.60 
$ 2.42 
$ 1.19 
Earnings (Loss) per Common Share – Diluted:
 
 
 
Continuing Operations - Diluted
$ 2.38 
$ 2.40 
$ 2.10 
Discontinued Operations - Diluted
$ 0.21 
$ 0.00 
$ (0.92)
Earnings (Loss) per Common Share – Diluted
$ 2.59 
$ 2.40 
$ 1.18 
Dividends per Common Share
$ 1.655 
$ 1.61 
$ 1.6 
Average Common Shares Outstanding - Basic
242.6 
242.6 
242.6 
Average Common Shares Outstanding - Diluted
243.6 
244.4 
244.5 
Union Electric Company
 
 
 
Operating Revenues:
 
 
 
Electric
3,470 
3,388 
3,379 
Gas
137 
164 
161 
Other
2 
1 
1 
Total operating revenues
3,609 
3,553 
3,541 
Operating Expenses:
 
 
 
Fuel
878 
826 
845 
Purchased power
111 
126 
133 
Gas purchased for resale
57 
82 
78 
Other operations and maintenance
925 
939 
909 
Provision for Callaway construction and operating license
69 
0 
0 
Depreciation and amortization
492 
473 
454 
Taxes other than income taxes
335 
322 
319 
Total operating expenses
2,867 
2,768 
2,738 
Operating Income
742 
785 
803 
Other Income and Expenses:
 
 
 
Miscellaneous income
52 
60 
58 
Miscellaneous expense
11 
12 
11 
Total other income (expense)
41 
48 
47 
Interest charges
219 
211 
210 
Income Before Income Taxes
564 
622 
640 
Income taxes
209 
229 
242 
Net Income (Loss)
355 
393 
398 
Other Comprehensive Income
0 
0 
0 
Comprehensive Income (Loss)
355 
393 
398 
Net Income (Loss):
 
 
 
Net income (loss) attributable to Ameren Corporation
355 
393 
398 
Preferred Stock Dividends
3 
3 
3 
Net Income Available to Common Stockholder
352 
390 
395 
Ameren Illinois Company
 
 
 
Operating Revenues:
 
 
 
Electric
1,683 
1,522 
1,461 
Gas
783 
976 
847 
Other
 
 
3 
Total operating revenues
2,466 
2,498 
2,311 
Operating Expenses:
 
 
 
Purchased power
420 
343 
380 
Gas purchased for resale
358 
533 
448 
Other operations and maintenance
797 
771 
693 
Depreciation and amortization
295 
263 
243 
Taxes other than income taxes
130 
138 
132 
Total operating expenses
2,000 
2,048 
1,896 
Operating Income
466 
450 
415 
Other Income and Expenses:
 
 
 
Miscellaneous income
21 
17 
10 
Miscellaneous expense
12 
8 
9 
Total other income (expense)
9 
9 
1 
Interest charges
131 
112 
143 
Income Before Income Taxes
344 
347 
273 
Income taxes
127 
143 
110 
Net Income (Loss)
217 
204 
163 
Pension and other postretirement activity, net of income taxes (benefit)
(3)
(3)
(3)
Comprehensive Income (Loss)
214 
201 
160 
Net Income (Loss):
 
 
 
Net income (loss) attributable to Ameren Corporation
217 
204 
163 
Preferred Stock Dividends
3 
3 
3 
Net Income Available to Common Stockholder
$ 214 
$ 201 
$ 160 
Consolidated Statement Of Income (Loss) (Parenthetical) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Pension and other postretirement activity, tax (benefit)
$ 3 
$ (7)
$ 16 
Ameren Illinois Company
 
 
 
Pension and other postretirement activity, tax (benefit)
$ (2)
$ (2)
$ (2)
Consolidated Statement Of Comprehensive Income (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Income from Continuing Operations
$ 585 
$ 593 
$ 518 
Pension and other postretirement activity, net of income taxes (benefit)
6 
(12)
30 
Comprehensive Income (Loss) from Continuing Operations
591 
581 
548 
Less: Comprehensive Income from Continuing Operations Attributable to Noncontrolling Interests
6 
6 
6 
Comprehensive Income from Continuing Operations Attributable to Ameren Corporation
585 
575 
542 
Income (Loss) from Discontinued Operations, Net of Tax (Note 16)
51 
(1)
(223)
Comprehensive Income from Continuing Operations Attributable to Ameren Corporation
 
0 
(18)
Comprehensive Income (Loss) from Discontinued Operations
51 
(1)
(241)
Less: Comprehensive Income from Discontinuing Operations Attributable to Noncontrolling Interest
 
0 
1 
Comprehensive Income (Loss) from Discontinued Operations Attributable to Ameren Corporation
51 
(1)
(242)
Comprehensive Income (Loss)
636 
574 
300 
Ameren Illinois Company
 
 
 
Pension and other postretirement activity, net of income taxes (benefit)
(3)
(3)
(3)
Comprehensive Income (Loss)
$ 214 
$ 201 
$ 160 
Consolidated Statement Of Comprehensive Income (Parenthetical) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Pension and other postretirement activity, tax (benefit)
$ 3 
$ (7)
$ 16 
Other Comprehensive Income (Loss) from Discontinued Operations Tax (Benefit)
$ 0 
$ 0 
$ (10)
Consolidated Balance Sheet (USD $)
In Millions, unless otherwise specified
Dec. 31, 2015
Dec. 31, 2014
Current Assets:
 
 
Cash and cash equivalents
$ 292 
$ 5 
Accounts receivable - trade (less allowance for doubtful accounts)
388 
423 
Unbilled revenue
239 
265 
Miscellaneous accounts and notes receivable
98 
81 
Materials and supplies
538 
524 
Current regulatory assets
260 
295 
Other current assets
88 
86 
Assets of discontinued operations (Note 16)
14 
15 
Total current assets
1,917 
1,694 
Property, Plant and Equipment, Net
18,799 1
17,424 1
Investments and Other Assets:
 
 
Nuclear decommissioning trust fund
556 
549 
Goodwill
411 
411 
Regulatory assets
1,382 
1,582 
Other assets
575 
629 
Total investments and other assets
2,924 
3,171 
TOTAL ASSETS
23,640 
22,289 
Current Liabilities:
 
 
Current maturities of long-term debt
395 
120 
Short-term debt
301 
714 
Accounts and wages payable
777 
711 
Taxes accrued
43 
46 
Interest accrued
89 
85 
Current regulatory liabilities
80 
106 
Other current liabilities
379 
434 
Liabilities of discontinued operations (Note 16)
29 
33 
Total current liabilities
2,093 
2,249 
Long-term Debt, Net
6,880 
6,085 
Deferred Credits and Other Liabilities:
 
 
Accumulated deferred income taxes, net
3,885 
3,571 
Accumulated deferred investment tax credits
60 
64 
Regulatory liabilities
1,905 
1,850 
Asset retirement obligations
618 
396 
Pension and other postretirement benefits
580 
705 
Other deferred credits and liabilities
531 
514 
Total deferred credits and other liabilities
7,579 
7,100 
Commitments and Contingencies (Notes 2, 10, 14 and 15)
   
   
Stockholders' Equity:
 
 
Common stock
2 
2 
Other paid-in capital, principally premium on common stock
5,616 
5,617 
Retained earnings
1,331 
1,103 
Accumulated other comprehensive income (loss)
(3)
(9)
Total stockholders' equity
6,946 
6,713 
Noncontrolling Interests
142 
142 
Total equity
7,088 
6,855 
TOTAL LIABILITIES AND EQUITY
23,640 
22,289 
Union Electric Company
 
 
Current Assets:
 
 
Cash and cash equivalents
199 
1 
Advances to money pool
36 
0 
Accounts receivable - trade (less allowance for doubtful accounts)
174 
190 
Accounts receivable - affiliates
54 
65 
Unbilled revenue
128 
146 
Miscellaneous accounts and notes receivable
78 
35 
Materials and supplies
387 
347 
Current regulatory assets
89 
163 
Other current assets
41 
43 
Total current assets
1,186 
990 
Property, Plant and Equipment, Net
11,183 1
10,867 1
Investments and Other Assets:
 
 
Nuclear decommissioning trust fund
556 
549 
Regulatory assets
605 
695 
Other assets
321 
373 
Total investments and other assets
1,482 
1,617 
TOTAL ASSETS
13,851 
13,474 
Current Liabilities:
 
 
Current maturities of long-term debt
266 
120 
Short-term debt
0 
97 
Accounts and wages payable
417 
405 
Accounts payable - affiliates
56 
56 
Taxes accrued
31 
32 
Interest accrued
59 
58 
Current regulatory liabilities
28 
18 
Other current liabilities
120 
117 
Total current liabilities
977 
903 
Long-term Debt, Net
3,844 
3,861 
Deferred Credits and Other Liabilities:
 
 
Accumulated deferred income taxes, net
2,844 
2,757 
Accumulated deferred investment tax credits
58 
61 
Regulatory liabilities
1,172 
1,147 
Asset retirement obligations
612 
389 
Pension and other postretirement benefits
234 
274 
Other deferred credits and liabilities
28 
30 
Total deferred credits and other liabilities
4,948 
4,658 
Commitments and Contingencies (Notes 2, 10, 14 and 15)
   
   
Stockholders' Equity:
 
 
Common stock
511 
511 
Other paid-in capital, principally premium on common stock
1,822 
1,569 
Preferred stock not subject to mandatory redemption
80 
80 
Retained earnings
1,669 
1,892 
Total stockholders' equity
4,082 
4,052 
TOTAL LIABILITIES AND EQUITY
13,851 
13,474 
Ameren Illinois Company
 
 
Current Assets:
 
 
Cash and cash equivalents
71 
1 
Accounts receivable - trade (less allowance for doubtful accounts)
204 
212 
Accounts receivable - affiliates
22 
22 
Unbilled revenue
111 
119 
Miscellaneous accounts and notes receivable
19 
9 
Materials and supplies
151 
177 
Current regulatory assets
167 
129 
Other current assets
15 
15 
Total current assets
760 
684 
Property, Plant and Equipment, Net
6,848 
6,165 
Investments and Other Assets:
 
 
Goodwill
411 
411 
Regulatory assets
771 
883 
Other assets
113 
61 
Total investments and other assets
1,295 
1,355 
TOTAL ASSETS
8,903 
8,204 
Current Liabilities:
 
 
Current maturities of long-term debt
129 
0 
Short-term debt
0 
32 
Borrowings from money pool
0 
15 
Accounts and wages payable
249 
207 
Accounts payable - affiliates
66 
50 
Taxes accrued
13 
17 
Customer deposits
69 
77 
Mark-to-market derivative liabilities
45 
42 
Environmental remediation
28 
52 
Current regulatory liabilities
39 
84 
Other current liabilities
114 
124 
Total current liabilities
752 
700 
Long-term Debt, Net
2,342 
2,224 
Deferred Credits and Other Liabilities:
 
 
Accumulated deferred income taxes, net
1,480 
1,248 
Accumulated deferred investment tax credits
2 
3 
Regulatory liabilities
732 
703 
Pension and other postretirement benefits
271 
277 
Accrued Environmental Loss Contingencies, Noncurrent
205 
199 
Other deferred credits and liabilities
222 
189 
Total deferred credits and other liabilities
2,912 
2,619 
Commitments and Contingencies (Notes 2, 10, 14 and 15)
   
   
Stockholders' Equity:
 
 
Common stock
0 
0 
Other paid-in capital, principally premium on common stock
2,005 
1,980 
Preferred stock not subject to mandatory redemption
62 
62 
Retained earnings
825 
611 
Accumulated other comprehensive income (loss)
5 
8 
Total stockholders' equity
2,897 
2,661 
TOTAL LIABILITIES AND EQUITY
$ 8,903 
$ 8,204 
Consolidated Balance Sheet (Parenthetical) (USD $)
In Millions, except Share data, unless otherwise specified
Dec. 31, 2015
Dec. 31, 2014
Accounts receivable - trade, allowance for doubtful accounts
$ 19 
$ 21 
Common stock, par value
$ 0.01 
$ 0.01 
Common stock, shares authorized
400,000,000 
400,000,000 
Common stock, shares outstanding
242,600,000 
242,600,000 
Union Electric Company
 
 
Accounts receivable - trade, allowance for doubtful accounts
7 
8 
Common stock, par value
$ 5 
$ 5 
Common stock, shares authorized
150,000,000 
150,000,000 
Common stock, shares outstanding
102,100,000 
102,100,000 
Ameren Illinois Company
 
 
Accounts receivable - trade, allowance for doubtful accounts
$ 12 
$ 13 
Common Stock, No Par Value
$ 0 
$ 0 
Common stock, shares authorized
45,000,000 
45,000,000 
Common stock, shares outstanding
25,500,000 
25,500,000 
Consolidated Statement Of Cash Flows (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Cash Flows From Operating Activities:
 
 
 
Net income (loss)
$ 636 
$ 592 
$ 295 
(Income) Loss from discontinued operations, net of tax
(51)
1 
223 
Adjustments to reconcile net income to net cash provided by operating activities:
 
 
 
Provision for Callaway construction and operating license
69 
 
0 
Depreciation and amortization
777 
710 
666 
Amortization of nuclear fuel
97 
81 
71 
Amortization of debt issuance costs and premium/discounts
22 
22 
24 
Deferred income taxes and investment tax credits, net
369 
451 
410 
Allowance for equity funds used during construction
(30)1
(34)1
(37)1
Share-based Compensation
24 
25 
27 
Other
(10)
(24)
23 
Changes in assets and liabilities:
 
 
 
Receivables
83 
31 
(60)
Materials and supplies
(14)
3 
60 
Accounts and wages payable
(2)
10 
81 
Taxes accrued
(24)
(44)
(195)
Regulatory assets and liabilities
94 
(281)
29 
Assets, other
53 
30 
20 
Liabilities, other
(56)
(28)
(14)
Pension and other postretirement benefits
(9)
(10)
(28)
Counterparty collateral, net
(7)
22 
41 
Net cash provided by operating activities - continuing operations
2,021 
1,557 
1,636 
Net cash provided by operating activities - discontinued operations
(4)
(6)
57 
Net cash provided by operating activities
2,017 
1,551 
1,693 
Cash Flows From Investing Activities:
 
 
 
Capital expenditures
(1,917)
(1,785)
(1,379)
Nuclear fuel expenditures
(52)
(74)
(45)
Purchases of securities - nuclear decommissioning trust fund
(363)
(405)
(214)
Sales and maturities of securities - nuclear decommissioning trust fund
349 
391 
196 
Proceeds from Collection of Notes Receivable
20 
95 
6 
Contributions to Note Receivable
(8)
(89)
(5)
Other
20 
11 
1 
Net cash used in investing activities - continuing operations
(1,951)
(1,856)
(1,440)
Net cash used in investing activities - discontinued operations
(25)
139 
(283)
Net cash used in investing activities
(1,976)
(1,717)
(1,723)
Cash Flows From Financing Activities:
 
 
 
Dividends on common stock
(402)
(390)
(388)
Dividends paid to noncontrolling interest holders
(6)
(6)
(6)
Short-term debt, net
(413)
346 
368 
Maturities, redemptions, and repurchases of long-term debt
(120)
(697)
(399)
Issuances of Long-term debt
1,197 
898 
278 
Capital issuance costs
(12)
(11)
(2)
Other
2 
1 
0 
Net cash provided by (used in) financing activities
246 
141 
(149)
Net change in cash and cash equivalents
287 
(25)
(179)
Cash and cash equivalents at beginning of year
5 
30 
209 
Cash and cash equivalents at end of year
292 
5 
30 
Cash Paid (Refunded) During the Year:
 
 
 
Interest net of capitalized
335 
333 
393 
Income taxes, net
(15)
(27)
8 
Union Electric Company
 
 
 
Cash Flows From Operating Activities:
 
 
 
Net income (loss)
355 
393 
398 
Adjustments to reconcile net income to net cash provided by operating activities:
 
 
 
Provision for Callaway construction and operating license
69 
0 
0 
Depreciation and amortization
476 
442 
419 
Amortization of nuclear fuel
97 
81 
71 
FAC prudence review charge
 
 
26 
Amortization of debt issuance costs and premium/discounts
6 
7 
7 
Deferred income taxes and investment tax credits, net
82 
245 
65 
Allowance for equity funds used during construction
(22)
(32)
(31)
Other
2 
3 
1 
Changes in assets and liabilities:
 
 
 
Receivables
72 
(10)
(59)
Materials and supplies
(39)
8 
45 
Accounts and wages payable
3 
25 
42 
Taxes accrued
1 
(197)
100 
Regulatory assets and liabilities
117 
(68)
68 
Assets, other
26 
52 
18 
Liabilities, other
4 
0 
(29)
Pension and other postretirement benefits
(2)
1 
2 
Net cash provided by operating activities
1,247 
950 
1,143 
Cash Flows From Investing Activities:
 
 
 
Capital expenditures
(622)
(747)
(648)
Nuclear fuel expenditures
(52)
(74)
(45)
Purchases of securities - nuclear decommissioning trust fund
(363)
(405)
(214)
Sales and maturities of securities - nuclear decommissioning trust fund
349 
391 
196 
Money pool advances, net
36 
 
(24)
Other
 
(2)
0 
Net cash used in investing activities
(724)
(837)
(687)
Cash Flows From Financing Activities:
 
 
 
Dividends on common stock
(575)
(340)
(460)
Return of capital to parent
0 
(215)
 
Dividends on preferred stock
(3)
(3)
(3)
Money pool borrowings, net
0 
(105)
105 
Short-term debt, net
(97)
97 
 
Maturities, redemptions, and repurchases of long-term debt
(120)
(109)
(249)
Issuances of Long-term debt
249 
350 
 
Capital issuance costs
(3)
(3)
 
Capital contribution from parent
224 
215 
4 
Net cash provided by (used in) financing activities
(325)
(113)
(603)
Net change in cash and cash equivalents
198 
0 
(147)
Cash and cash equivalents at beginning of year
1 
1 
148 
Cash and cash equivalents at end of year
199 
1 
1 
Noncash Or Part Noncash Capital Contribution From Parent
38 
9 
0 
Cash Paid (Refunded) During the Year:
 
 
 
Interest net of capitalized
212 
203 
212 
Income taxes, net
72 
215 
86 
Ameren Illinois Company
 
 
 
Cash Flows From Operating Activities:
 
 
 
Net income (loss)
217 
204 
163 
Adjustments to reconcile net income to net cash provided by operating activities:
 
 
 
Depreciation and amortization
292 
259 
238 
Amortization of debt issuance costs and premium/discounts
14 
13 
15 
Deferred income taxes and investment tax credits, net
221 
196 
104 
Allowance for equity funds used during construction
(8)
(2)
(6)
Other
(14)
(19)
4 
Changes in assets and liabilities:
 
 
 
Receivables
16 
(13)
50 
Materials and supplies
25 
(4)
15 
Accounts and wages payable
37 
7 
19 
Taxes accrued
(2)
(7)
28 
Regulatory assets and liabilities
(26)
(215)
(35)
Assets, other
17 
15 
5 
Liabilities, other
(27)
1 
10 
Pension and other postretirement benefits
(4)
(6)
(8)
Counterparty collateral, net
(3)
14 
43 
Net cash provided by operating activities
763 
445 
651 
Cash Flows From Investing Activities:
 
 
 
Capital expenditures
(918)
(835)
(701)
Other
5 
7 
6 
Net cash used in investing activities
(913)
(828)
(695)
Cash Flows From Financing Activities:
 
 
 
Dividends on common stock
 
0 
(110)
Dividends on preferred stock
(3)
(3)
(3)
Money pool borrowings, net
(15)
(41)
32 
Short-term debt, net
(32)
32 
 
Maturities, redemptions, and repurchases of long-term debt
0 
(163)
(150)
Issuances of Long-term debt
248 
548 
278 
Capital issuance costs
(3)
(6)
(2)
Capital contribution from parent
25 
15 
 
Other
 
1 
0 
Net cash provided by (used in) financing activities
220 
383 
45 
Net change in cash and cash equivalents
70 
0 
1 
Cash and cash equivalents at beginning of year
1 
1 
0 
Cash and cash equivalents at end of year
71 
1 
1 
Cash Paid (Refunded) During the Year:
 
 
 
Interest net of capitalized
120 
110 
112 
Income taxes, net
$ (113)
$ (44)
$ (23)
Consolidated Statement Of Cash Flows (Parenthetical) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Capitalized interest
$ 17 
$ 18 
$ 37 
Union Electric Company
 
 
 
Capitalized interest
12 
16 
16 
Ameren Illinois Company
 
 
 
Capitalized interest
$ 5 
$ 2 
$ 4 
Consolidated Statement Of Stockholders' Equity (USD $)
In Millions, unless otherwise specified
Total
Common Stock
Other Paid-In Capital
Retained Earnings
Derivative Financial Instruments
Deferred Retirement Benefit Costs
Accumulated Other Comprehensive Income (Loss)
Noncontrolling Interest
Total Ameren Corporation Stockholders' Equity
Union Electric Company
Union Electric Company
Common Stock
Union Electric Company
Other Paid-In Capital
Union Electric Company
Preferred Stock Not Subject To Mandatory Redemption
Union Electric Company
Retained Earnings
Ameren Illinois Company
Ameren Illinois Company
Common Stock
Ameren Illinois Company
Other Paid-In Capital
Ameren Illinois Company
Preferred Stock Not Subject To Mandatory Redemption
Ameren Illinois Company
Retained Earnings
Ameren Illinois Company
Deferred Retirement Benefit Costs
Ameren Illinois Company
Accumulated Other Comprehensive Income (Loss)
Beginning of year at Dec. 31, 2012
 
$ 2 
$ 5,616 
$ 1,006 
$ 25 
$ (33)
 
$ 151 
 
 
 
$ 1,556 
 
$ 1,907 
 
 
$ 1,965 
 
$ 360 
$ 14 
 
Increase (Decrease) in Stockholders' Equity [Roll Forward]
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Stock-based compensation activity
 
 
16 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Net income (loss) attributable to Ameren Corporation
289 
 
 
289 
 
 
 
 
 
398 
 
 
 
 
163 
 
 
 
 
 
 
Net income (loss)
295 
 
 
 
 
 
 
 
 
398 
 
 
 
398 
163 
 
 
 
163 
 
 
Common stock dividends
 
 
 
(388)
 
 
 
 
 
 
 
 
 
(460)
 
 
 
 
(110)
 
 
Capital contribution from parent
 
 
 
 
 
 
 
 
 
4 
 
4 
 
 
 
 
0 
 
 
 
 
Preferred stock dividends
 
 
 
 
 
 
 
 
 
 
 
 
 
(3)
 
 
 
 
(3)
 
 
Change in derivative financial instruments
 
 
 
 
(21)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Divestiture of derivative financial instruments
 
 
 
 
(4)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Change in deferred retirement benefit costs
(30)
 
 
 
 
29 
 
 
 
 
 
 
 
 
3 
 
 
 
 
 
(3)
Divestiture of deferred retirement benefit costs
 
 
 
 
 
7 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Net income attributable to noncontrolling interest holder
 
 
 
 
 
 
 
6 
 
 
 
 
 
 
 
 
 
 
 
 
 
Dividends paid to noncontrolling interest holders
 
 
 
 
 
 
 
(6)
 
 
 
 
 
 
 
 
 
 
 
 
 
Divestiture of noncontrolling interest
 
 
 
 
 
 
 
(9)
 
 
 
 
 
 
 
 
 
 
 
 
 
Return of capital to parent
 
 
 
 
 
 
 
 
 
 
 
0 
 
 
 
 
 
 
 
 
 
Stockholders' equity, end of year at Dec. 31, 2013
 
 
 
 
 
 
 
 
6,544 
3,993 
 
 
 
 
2,448 
 
 
 
 
 
 
End of year at Dec. 31, 2013
6,686 
2 
5,632 
907 
0 
3 
3 
142 
 
 
511 
1,560 
80 
1,842 
 
0 
1,965 
62 
410 
11 
11 
End of year (shares) at Dec. 31, 2013
242.6 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Increase (Decrease) in Stockholders' Equity [Roll Forward]
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Net income (loss) attributable to Ameren Corporation
96 
 
 
 
 
 
 
 
 
48 
 
 
 
 
54 
 
 
 
 
 
 
Net income (loss)
98 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Stockholders' equity, end of year at Mar. 31, 2014
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Beginning of year at Dec. 31, 2013
6,686 
2 
5,632 
907 
0 
3 
3 
142 
 
 
511 
1,560 
80 
1,842 
 
0 
1,965 
62 
410 
11 
11 
Beginning of year (shares) at Dec. 31, 2013
242.6 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Increase (Decrease) in Stockholders' Equity [Roll Forward]
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Stock-based compensation activity
 
 
(15)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Net income (loss) attributable to Ameren Corporation
586 
 
 
586 
 
 
 
 
 
393 
 
 
 
 
204 
 
 
 
 
 
 
Net income (loss)
592 
 
 
 
 
 
 
 
 
393 
 
 
 
393 
204 
 
 
 
204 
 
 
Common stock dividends
 
 
 
(390)
 
 
 
 
 
 
 
 
 
(340)
 
 
 
 
0 
 
 
Capital contribution from parent
 
 
 
 
 
 
 
 
 
215 
 
224 
 
 
15 
 
15 
 
 
 
 
Preferred stock dividends
 
 
 
 
 
 
 
 
 
 
 
 
 
(3)
 
 
 
 
(3)
 
 
Change in derivative financial instruments
 
 
 
 
0 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Divestiture of derivative financial instruments
 
 
 
 
0 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Change in deferred retirement benefit costs
12 
 
 
 
 
(12)
 
 
 
 
 
 
 
 
3 
 
 
 
 
 
(3)
Divestiture of deferred retirement benefit costs
 
 
 
 
 
0 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Net income attributable to noncontrolling interest holder
 
 
 
 
 
 
 
6 
 
 
 
 
 
 
 
 
 
 
 
 
 
Dividends paid to noncontrolling interest holders
 
 
 
 
 
 
 
(6)
 
 
 
 
 
 
 
 
 
 
 
 
 
Divestiture of noncontrolling interest
 
 
 
 
 
 
 
0 
 
 
 
 
 
 
 
 
 
 
 
 
 
Return of capital to parent
 
 
 
 
 
 
 
 
 
215 
 
(215)
 
 
 
 
 
 
 
 
 
Stockholders' equity, end of year at Dec. 31, 2014
6,713 
 
 
 
 
 
 
 
6,713 
4,052 
 
 
 
 
2,661 
 
 
 
 
 
 
End of year at Dec. 31, 2014
6,855 
2 
5,617 
1,103 
0 
(9)
(9)
142 
 
 
511 
1,569 
80 
1,892 
 
0 
1,980 
62 
611 
8 
8 
End of year (shares) at Dec. 31, 2014
242.6 
 
 
 
 
 
 
 
 
102.1 
 
 
 
 
25.5 
 
 
 
 
 
 
Beginning of year at Sep. 30, 2014
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Increase (Decrease) in Stockholders' Equity [Roll Forward]
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Net income (loss) attributable to Ameren Corporation
48 
 
 
 
 
 
 
 
 
(5)
 
 
 
 
46 
 
 
 
 
 
 
Net income (loss)
49 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Stockholders' equity, end of year at Dec. 31, 2014
6,713 
 
 
 
 
 
 
 
6,713 
4,052 
 
 
 
 
2,661 
 
 
 
 
 
 
End of year at Dec. 31, 2014
6,855 
2 
 
 
 
 
(9)
 
 
 
511 
 
80 
 
 
0 
 
62 
 
8 
 
End of year (shares) at Dec. 31, 2014
242.6 
 
 
 
 
 
 
 
 
102.1 
 
 
 
 
25.5 
 
 
 
 
 
 
Increase (Decrease) in Stockholders' Equity [Roll Forward]
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Net income (loss) attributable to Ameren Corporation
108 
 
 
 
 
 
 
 
 
42 
 
 
 
 
54 
 
 
 
 
 
 
Net income (loss)
110 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Stockholders' equity, end of year at Mar. 31, 2015
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Beginning of year at Dec. 31, 2014
6,855 
2 
5,617 
1,103 
0 
(9)
(9)
142 
 
 
511 
1,569 
80 
1,892 
 
0 
1,980 
62 
611 
8 
8 
Beginning of year (shares) at Dec. 31, 2014
242.6 
 
 
 
 
 
 
 
 
102.1 
 
 
 
 
25.5 
 
 
 
 
 
 
Increase (Decrease) in Stockholders' Equity [Roll Forward]
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Stock-based compensation activity
 
 
(1)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Net income (loss) attributable to Ameren Corporation
630 
 
 
630 
 
 
 
 
 
355 
 
 
 
 
217 
 
 
 
 
 
 
Net income (loss)
636 
 
 
 
 
 
 
 
 
355 
 
 
 
355 
217 
 
 
 
217 
 
 
Common stock dividends
 
 
 
(402)
 
 
 
 
 
 
 
 
 
(575)
 
 
 
 
0 
 
 
Capital contribution from parent
 
 
 
 
 
 
 
 
 
224 
 
253 
 
 
25 
 
25 
 
 
 
 
Preferred stock dividends
 
 
 
 
 
 
 
 
 
 
 
 
 
(3)
 
 
 
 
(3)
 
 
Change in derivative financial instruments
 
 
 
 
0 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Divestiture of derivative financial instruments
 
 
 
 
0 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Change in deferred retirement benefit costs
(6)
 
 
 
 
6 
 
 
 
 
 
 
 
 
3 
 
 
 
 
 
(3)
Divestiture of deferred retirement benefit costs
 
 
 
 
 
0 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Net income attributable to noncontrolling interest holder
 
 
 
 
 
 
 
6 
 
 
 
 
 
 
 
 
 
 
 
 
 
Dividends paid to noncontrolling interest holders
 
 
 
 
 
 
 
(6)
 
 
 
 
 
 
 
 
 
 
 
 
 
Divestiture of noncontrolling interest
 
 
 
 
 
 
 
0 
 
 
 
 
 
 
 
 
 
 
 
 
 
Return of capital to parent
 
 
 
 
 
 
 
 
 
0 
 
0 
 
 
 
 
 
 
 
 
 
Stockholders' equity, end of year at Dec. 31, 2015
6,946 
 
 
 
 
 
 
 
6,946 
4,082 
 
 
 
 
2,897 
 
 
 
 
 
 
End of year at Dec. 31, 2015
7,088 
2 
5,616 
1,331 
0 
(3)
(3)
142 
 
 
511 
1,822 
80 
1,669 
 
0 
2,005 
62 
825 
5 
5 
End of year (shares) at Dec. 31, 2015
242.6 
 
 
 
 
 
 
 
 
102.1 
 
 
 
 
25.5 
 
 
 
 
 
 
Beginning of year at Sep. 30, 2015
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Increase (Decrease) in Stockholders' Equity [Roll Forward]
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Net income (loss) attributable to Ameren Corporation
29 
 
 
 
 
 
 
 
 
11 
 
 
 
 
33 
 
 
 
 
 
 
Net income (loss)
30 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Stockholders' equity, end of year at Dec. 31, 2015
6,946 
 
 
 
 
 
 
 
6,946 
4,082 
 
 
 
 
2,897 
 
 
 
 
 
 
End of year at Dec. 31, 2015
$ 7,088 
$ 2 
 
 
 
 
$ (3)
 
 
 
$ 511 
 
$ 80 
 
 
$ 0 
 
$ 62 
 
$ 5 
 
End of year (shares) at Dec. 31, 2015
242.6 
 
 
 
 
 
 
 
 
102.1 
 
 
 
 
25.5 
 
 
 
 
 
 
Summary Of Significant Accounting Policies
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
General
Ameren, headquartered in St. Louis, Missouri, is a public utility holding company under PUHCA 2005. Ameren’s primary assets are its equity interests in its subsidiaries, including Ameren Missouri and Ameren Illinois. Ameren’s subsidiaries are separate, independent legal entities with separate businesses, assets, and liabilities. Dividends on Ameren’s common stock and the payment of expenses by Ameren depend on distributions made to it by its subsidiaries. Ameren’s principal subsidiaries are listed below.
•
Union Electric Company, doing business as Ameren Missouri, operates a rate-regulated electric generation, transmission, and distribution business and a rate-regulated natural gas transmission and distribution business in Missouri. Ameren Missouri was incorporated in Missouri in 1922 and is successor to a number of companies, the oldest of which was organized in 1881. It is the largest electric utility in the state of Missouri. It supplies electric and natural gas service to a 24,000-square-mile area in central and eastern Missouri. This area has an estimated population of 2.8 million and includes the Greater St. Louis area. Ameren Missouri supplies electric service to 1.2 million customers and natural gas service to 0.1 million customers.
•
Ameren Illinois Company, doing business as Ameren Illinois, operates rate-regulated electric and natural gas transmission and distribution businesses in Illinois. Ameren Illinois was created by the merger of CILCO and IP with and into CIPS in 2010. CIPS was incorporated in Illinois in 1923 and was the successor to a number of companies, the oldest of which was organized in 1902. Ameren Illinois supplies electric and natural gas utility service to portions of central and southern Illinois having an estimated population of 3.1 million in an area of 40,000 square miles. Ameren Illinois supplies electric service to 1.2 million customers and natural gas service to 0.8 million customers.
Ameren has various other subsidiaries that conduct activities such as the provision of shared services. Ameren also has a subsidiary, ATXI, that operates a FERC rate-regulated electric transmission business. ATXI is developing MISO-approved electric transmission projects, including the Illinois Rivers, Spoon River, and Mark Twain projects. Ameren is also pursuing projects to improve electric transmission system reliability within Ameren Missouri's and Ameren Illinois' service territories as well as competitive electric transmission investment opportunities outside of these territories, including investments outside of MISO.
In December 2013, Ameren completed the divestiture of New AER to IPH. In January 2014, Medina Valley completed its sale of the Elgin, Gibson City, and Grand Tower gas-fired energy centers to Rockland Capital. In addition, in 2013, Ameren abandoned the Meredosia and Hutsonville energy centers upon the completion of the divestiture of New AER to IPH. Ameren is demolishing the Hutsonville energy center and expects to demolish the Meredosia energy center beginning in 2016. As a result of these events, Ameren has segregated New AER’s and the Elgin, Gibson City, Grand Tower, Meredosia, and Hutsonville energy centers’ operating results, assets, and liabilities and presented them separately as discontinued operations for all periods presented in this report. Unless otherwise stated, these notes to the financial statements exclude discontinued operations for all periods presented. See Note 16 – Divestiture Transactions and Discontinued Operations for additional information regarding these transactions.
Ameren's financial statements are prepared on a consolidated basis, and therefore include the accounts of its majority-owned subsidiaries. Ameren Missouri and Ameren Illinois have no subsidiaries and therefore their financial statements are not prepared on a consolidated basis. All intercompany transactions have been eliminated. All tabular dollar amounts are in millions, unless otherwise indicated.
Our accounting policies conform to GAAP. Our financial statements reflect all adjustments (which include normal, recurring adjustments) that are necessary, in our opinion, for a fair presentation of our results. The preparation of financial statements in conformity with GAAP requires management to make certain estimates and assumptions. Such estimates and assumptions affect reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the dates of financial statements, and the reported amounts of revenues and expenses during the reported periods. Actual results could differ from those estimates.
Regulation
We are regulated by the MoPSC, the ICC, and the FERC. We defer certain costs as assets pursuant to actions of rate regulators or because of expectations that we will be able to recover such costs in future rates charged to customers. We also defer certain amounts as liabilities pursuant to actions of rate regulators or based on the expectation that such amounts will be returned to customers in future rates. Regulatory assets and liabilities are amortized consistent with the period of expected regulatory treatment. In addition to the cost recovery mechanisms discussed in the Purchased Gas, Power, and Fuel Rate-adjustment Mechanisms section below, Ameren Missouri and Ameren Illinois have approvals from rate regulators to use other cost recovery mechanisms. Ameren Missouri has a pension and postretirement benefit cost tracker, an uncertain tax positions tracker, a renewable energy standards cost tracker, a solar rebate program tracker, and the MEEIA energy efficiency rider. Ameren Illinois' and ATXI's electric transmission rates are determined pursuant to formula ratemaking. Additionally, Ameren Illinois' electric distribution business participates in the performance-based formula ratemaking process established pursuant to the IEIMA. Ameren Illinois also has an environmental cost rider, an asbestos-related litigation rider, an energy efficiency rider, a QIP rider, a VBA rider, and a bad debt rider. See Note 2 – Rate and Regulatory Matters for additional information on regulatory assets and liabilities.
Cash and Cash Equivalents
Cash and cash equivalents include cash on hand and temporary investments purchased with an original maturity of three months or less.
Allowance for Doubtful Accounts Receivable
The allowance for doubtful accounts represents our estimate of existing accounts receivable that will ultimately be uncollectible. The allowance is calculated by applying estimated loss factors to various classes of outstanding receivables, including unbilled revenue. The loss factors used to estimate uncollectible accounts are based upon both historical collections experience and management’s estimate of future collections success given the existing and anticipated future collections environment. Ameren Illinois has a bad debt rider that adjusts rates for net write-offs of customer accounts receivable above or below those being collected in rates.
Materials and Supplies
Materials and supplies are recorded at the lower of cost or market. Cost is determined by the average-cost method. Materials and supplies are capitalized as inventory when purchased and then expensed or capitalized as plant assets when installed, as appropriate. The following table presents a breakdown of materials and supplies for each of the Ameren Companies at December 31, 2015 and 2014:
 
 
Ameren Missouri
 
Ameren Illinois
 
Ameren
2015
 
 
 
 
 
 
Fuel(a)
 
$
173

 
$
—

 
$
173

Gas stored underground
 
10

 
87

 
97

Other materials and supplies
 
204

 
64

 
268

Total materials and supplies
 
$
387

 
$
151

 
$
538

2014
 
 
 
 
 
 
Fuel(a)
 
$
134

 
$
—

 
$
134

Gas stored underground
 
16

 
111

 
127

Other materials and supplies
 
197

 
66

 
263

Total materials and supplies
 
$
347

 
$
177

 
$
524

(a)
Consists of coal, oil, and propane.
Purchased Gas, Power and Fuel Rate-adjustment Mechanisms
Ameren Missouri and Ameren Illinois have various rate-adjustment mechanisms in place that provide for the recovery of purchased natural gas and electric fuel and purchased power costs without a traditional rate case proceeding. See Note 2 – Rate and Regulatory Matters for the regulatory assets and liabilities recorded at December 31, 2015 and 2014, related to the rate-adjustment mechanisms discussed below.
In Ameren Missouri’s and Ameren Illinois’ natural gas utility jurisdictions, changes in natural gas costs are reflected in billings to their natural gas utility customers through PGA clauses. The difference between actual natural gas costs and costs billed to customers in a given period is deferred as a regulatory asset or liability. The deferred amount is either billed or refunded to natural gas utility customers in a subsequent period.
In Ameren Illinois’ retail electric utility jurisdiction, changes in purchased power and transmission service costs are reflected in billings to its electric utility customers through pass-through rate-adjustment clauses. The difference between actual purchased power and transmission service costs and costs billed to customers in a given period is deferred as a regulatory asset or liability. The deferred amount is either billed or refunded to electric utility customers in a subsequent period.
Ameren Missouri has a FAC that allows an adjustment of electric rates three times per year for a pass-through to customers of 95% of changes in fuel and purchased power costs, including transportation charges and revenues, net of off-system sales, greater or less than the amount set in base rates, subject to MoPSC prudence review. The difference between the actual amounts incurred for these items and the amounts recovered from Ameren Missouri customers' base rates is deferred as a regulatory asset or liability. The deferred amounts are either billed or refunded to electric utility customers in a subsequent period. As of May 30, 2015, transmission revenues and substantially all transmission charges are excluded from net energy costs as a result of the April 2015 MoPSC electric rate order.

Property and Plant, Net
We capitalize the cost of additions to and betterments of units of property and plant. The cost includes labor, material, applicable taxes, and overhead. An allowance for funds used during construction, as discussed below, is also capitalized as a cost of our rate-regulated assets. Maintenance expenditures, including nuclear refueling and maintenance outages, are expensed as incurred. When units of depreciable property are retired, the original costs, less salvage values, are charged to accumulated depreciation. If environmental expenditures are related to assets currently in use, as in the case of the installation of pollution control equipment, the cost is capitalized and depreciated over the expected life of the asset. See Asset Retirement Obligations below and Note 3 – Property and Plant, Net, for additional information.
Depreciation
Depreciation is provided over the estimated lives of the various classes of depreciable property by applying composite rates on a straight-line basis to the cost basis of such property. The provision for depreciation for the Ameren Companies in 2015, 2014, and 2013 ranged from 3% to 4% of the average depreciable cost.
Allowance for Funds Used During Construction
We capitalize allowance for funds used during construction, or the cost of borrowed funds and the cost of equity funds (preferred and common shareholders’ equity) applicable to rate-regulated construction expenditures, in accordance with the utility industry's accounting practice. Allowance for funds used during construction does not represent a current source of cash funds. This accounting practice offsets the effect on earnings of the cost of financing during construction, and it treats such financing costs in the same manner as construction charges for labor and materials.
Under accepted ratemaking practice, cash recovery of allowance for funds used during construction and other construction costs occurs when completed projects are placed in service and reflected in customer rates. The following table presents the annual allowance for funds used during construction rates that were applied to construction projects in 2015, 2014, and 2013:
 
2015
 
2014
 
2013
Ameren Missouri
7
%
 
7
%
 
8
%
Ameren Illinois
6
%
 
2
%
 
8
%

Goodwill
Goodwill represents the excess of the purchase price of an acquisition over the fair value of the net assets acquired. Ameren and Ameren Illinois' carrying amount of goodwill was $411 million at December 31, 2015, and 2014. All of Ameren's and Ameren Illinois' goodwill at December 31, 2015 and 2014, was assigned to the Ameren Illinois reporting unit.
We evaluate goodwill for impairment as of October 31 each year, or more frequently if events and circumstances change that would more likely than not reduce the fair value of the Ameren Illinois reporting unit below its carrying amount. Entities assessing goodwill for impairment have the option of first performing a qualitative assessment before calculating the fair value of the reporting unit. If an entity determines, on the basis of qualitative factors, that the fair value of the reporting unit is more likely than not less than the carrying amount, a two-step quantitative test is required. An entity has the option to bypass the qualitative assessment in any period and proceed directly to the first step of the quantitative test, which compares the fair value of the reporting unit to its carrying amount. If the carrying amount of the reporting unit exceeds its estimated fair value, the entity performs the second step, which requires an assignment of the reporting unit's fair value to the individual assets and liabilities in order to determine the implied fair value of the reporting unit's goodwill. If the implied fair value of goodwill is less than its carrying amount, an impairment loss is recorded.
Ameren and Ameren Illinois elected to bypass the qualitative assessment and completed the first step of the quantitative test as of October 31, 2015. Based on the results, Ameren and Ameren Illinois determined that the estimated fair value of the Ameren Illinois reporting unit significantly exceeded its carrying value as of October 31, 2015, indicating no impairment of Ameren’s or Ameren Illinois’ goodwill. Ameren's and Ameren Illinois' valuation approach is based on a market participant view. It uses a weighted combination of a discounted cash flow analysis and a market multiples analysis. Significant assumptions used in estimating the fair value of the Ameren Illinois reporting unit include discount and growth rates, utility sector market performance and transactions, and projected operating results and cash flows.
The goodwill assigned to the Ameren Illinois reporting unit on the December 31, 2015 balance sheets of Ameren and Ameren Illinois had no accumulated goodwill impairment losses. Ameren and Ameren Illinois will continue to monitor internal and external factors for signs of possible declines in estimated fair value and potential goodwill impairment.
Impairment of Long-lived Assets
We evaluate long-lived assets classified as held and used for impairment when events or changes in circumstances indicate that the carrying value of such assets may not be recoverable. Whether an impairment has occurred is determined by comparing the estimated undiscounted cash flows attributable to the assets to the carrying value of the assets. If the carrying value exceeds the undiscounted cash flows, we recognize an impairment charge equal to the amount by which the carrying value exceeds the estimated fair value of the assets. In the period in which we determine an asset meets held for sale criteria, we record an impairment charge to the extent the book value exceeds its estimated fair value less cost to sell. We did not identify any events or changes in circumstances that indicated that the carrying value of long-lived assets may not be recoverable in 2015 and 2014.
Environmental Costs
Liabilities for environmental costs are recorded on an undiscounted basis when it is probable that a liability has been incurred and the amount of the liability can be reasonably estimated. Costs are expensed or deferred as a regulatory asset when it is expected that the costs will be recovered from customers in future rates.
Asset Retirement Obligations
We are required to record the estimated fair value of legal obligations associated with the retirement of tangible long-lived assets in the period in which the liabilities are incurred and to capitalize a corresponding amount as part of the book value of the related long-lived asset. In subsequent periods, we are required to make adjustments to AROs based on changes in the estimated fair values of the obligations. Corresponding increases in asset book values are depreciated over the remaining useful life of the related asset. Uncertainties as to the probability, timing, or amount of cash expenditures associated with AROs affect our estimates of fair value. Ameren and Ameren Missouri have recorded AROs for retirement costs associated with Ameren Missouri’s Callaway energy center decommissioning costs, CCR facilities, and river structures. Also, Ameren, Ameren Missouri, and Ameren Illinois have recorded AROs for retirement costs associated with asbestos removal and the disposal of certain transformers. Ameren and Ameren Missouri have a nuclear decommissioning trust fund for the decommissioning of the Callaway energy center. Asset removal costs accrued by our rate-regulated operations that do not constitute legal obligations are classified as regulatory liabilities. See Note 2 – Rate and Regulatory Matters.
The following table provides a reconciliation of the beginning and ending carrying amount of AROs for the years ended December 31, 2015 and 2014:
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
 
Balance at December 31, 2013
$
366

 
$
3

 
$
369

 
Liabilities incurred
2

 
—

 
2

 
Liabilities settled
(2
)
 
(a)

 
(2
)
 
Accretion in 2014(b)
21

 
(a)

 
21

 
Change in estimates(c)
2

 
4

 
6

 
Balance at December 31, 2014
$
389

 
$
7

(d) 
$
396

 
Liabilities incurred
3

 
—

 
3

 
Liabilities settled
(1
)
 
(1
)
 
(2
)
 
Accretion in 2015(b)
23

 
(a)

 
23

 
Change in estimates(e)
203

 
(a)

 
203

 
Balance at December 31, 2015
$
617

(f) 
$
6

(d) 
$
623

(f) 

(a)
Less than $1 million.
(b)
Accretion expense was recorded as an increase to regulatory assets at Ameren Missouri and Ameren Illinois.
(c)
The ARO increase resulted in a corresponding increase recorded to "Property and Plant, Net." Ameren Illinois changed its fair value estimate for asbestos removal.
(d)
Included in “Other deferred credits and liabilities” on the balance sheet.
(e)
The ARO increase resulted in a corresponding increase recorded to "Property and Plant, Net." Ameren and Ameren Missouri increased their AROs related to the decommissioning of the Callaway energy center by $99 million to reflect the 2015 cost study and funding analysis filed with the MoPSC, the extension of the estimated operating life until 2044, and a reduction in the discount rate assumption. See Note 10 – Callaway Energy Center for additional information. In addition, as a result of new federal regulations, Ameren and Ameren Missouri recorded an increase of $100 million to their AROs associated with CCR storage facilities. See Note 15 – Commitments and Contingencies for additional information. Ameren and Ameren Missouri also increased their AROs by $4 million due to a change in the estimated retirement dates of the Meramec and Rush Island energy centers as a result of the MoPSC's April 2015 electric rate order.
(f)
Balance included $5 million in "Other current liabilities" on the balance sheet as of December 31, 2015.
See Note 16 – Divestiture Transactions and Discontinued Operations for additional information on the AROs related to the abandoned Meredosia and Hutsonville energy centers, which are presented as discontinued operations and therefore not included in the table above.
Noncontrolling Interests
As of December 31, 2015 and 2014, Ameren’s noncontrolling interests included the preferred stock of Ameren Missouri and Ameren Illinois.
Operating Revenue
The Ameren Companies record operating revenue for electric or natural gas service when it is delivered to customers. We accrue an estimate of electric and natural gas revenues for service rendered but unbilled at the end of each accounting period.
Ameren Illinois participates in the performance-based formula ratemaking framework pursuant to the IEIMA. In addition, Ameren Illinois' and ATXI's electric transmission delivery service operating revenues are regulated by the FERC. The provisions of the IEIMA and the FERC's electric transmission formula rate framework provide for annual reconciliations of the electric delivery and electric transmission service revenue requirements necessary to reflect the actual recoverable costs incurred in a given year with the revenue requirements in customer rates for that year, including an allowed return on equity. In each of those electric jurisdictions, if the current year's revenue requirement is greater than the revenue requirement reflected in that year's customer rates, an increase to electric operating revenues with an offset to a regulatory asset is recorded to reflect the expected recovery of those additional amounts from customers within the next two years. In each jurisdiction, if the current year's revenue requirement is less than the revenue requirement reflected in that year's customer rates, a reduction to electric operating revenues with an offset to a regulatory liability is recorded to reflect the expected refund to customers within the next two years. See Note 2 – Rate and Regulatory Matters for information regarding Ameren Illinois' revenue requirement reconciliation pursuant to the IEIMA.
Accounting for MISO Transactions
MISO-related purchase and sale transactions are recorded by Ameren, Ameren Missouri, and Ameren Illinois using settlement information provided by MISO. Ameren Missouri records these purchase and sale transactions on a net hourly position. Ameren Missouri records net purchases in a single hour in “Operating Expenses – Purchased power” and net sales in a single hour in “Operating Revenues – Electric” in its statement of income. Ameren Illinois records net purchases in “Operating Expenses – Purchased power” in its statement of income to reflect all of its MISO transactions relating to the procurement of power for its customers. On occasion, Ameren Missouri's and Ameren Illinois' prior-period transactions will be resettled outside the routine settlement process because of a change in MISO’s tariff or a material interpretation thereof. In these cases, Ameren Missouri and Ameren Illinois recognize expenses associated with resettlements once the resettlement is probable and the resettlement amount can be estimated and recognize revenues once the resettlement amount is received.
Nuclear Fuel
Ameren Missouri’s cost of nuclear fuel is capitalized and then amortized to fuel expense on a unit-of-production basis. The cost is charged to "Operating Expenses – Fuel" in the statement of income.
Stock-based Compensation
Stock-based compensation cost is measured at the grant date based on the fair value of the award, net of an assumed forfeiture rate. Ameren recognizes as compensation expense the estimated fair value of stock-based compensation on a straight-line basis over the requisite service period. See Note 12 – Stock-based Compensation for additional information.
Excise Taxes
Ameren Missouri and Ameren Illinois collect from their customers certain excise taxes that are levied on the sale or distribution of natural gas and electricity. Excise taxes are levied on Ameren Missouri's electric and natural gas businesses and on Ameren Illinois' natural gas business. They are recorded gross in “Operating Revenues – Electric,” “Operating Revenues – Gas,” and “Operating Expenses – Taxes other than income taxes” on the statement of income or the statement of income and comprehensive income. Excise taxes for electric service in Illinois are levied on customers and are therefore not included in Ameren Illinois' revenues and expenses. The following table presents the excise taxes recorded in “Operating Revenues – Electric,” “Operating Revenues – Gas,” and “Operating Expenses – Taxes other than income taxes” for the years ended December 31, 2015, 2014, and 2013:
 
2015
 
2014
 
2013
Ameren Missouri
$
156

 
$
151

 
$
152

Ameren Illinois
57

 
64

 
61

Ameren
$
213

 
$
215

 
$
213


Unamortized Debt Discounts, Premiums, and Issuance Costs
Long-term debt discounts, premiums, and issuance costs are amortized over the lives of the related issuances. Credit facility fees are amortized over the credit facility term.
Income Taxes
Ameren uses an asset and liability approach for its financial accounting and reporting of income taxes, in accordance with authoritative accounting guidance. Deferred tax assets and liabilities are recognized for transactions that are treated differently for financial reporting and income tax return purposes. These deferred tax assets and liabilities are based on statutory tax rates.
We recognize that regulators will probably reduce future revenues for deferred tax liabilities that were initially recorded at rates in excess of the current statutory rate. Therefore, reductions in deferred tax liabilities that were recorded because of decreases in the statutory rate have been credited to a regulatory liability. A regulatory asset has been established to recognize the probable recovery through future customer rates of tax benefits related to the equity component of allowance for funds used during construction, as well as the effects of tax rate changes.
Investment tax credits used on tax returns for prior years have been deferred as a noncurrent liability. The credits are being amortized over the useful lives of the related investment. Deferred income taxes were recorded on the temporary difference represented by the deferred investment tax credits and a corresponding regulatory liability. This recognizes the expected reduction in rates for future lower income taxes associated with the amortization of the investment tax credits. See Note 13 – Income Taxes.
Ameren Missouri, Ameren Illinois, and all the other Ameren subsidiary companies are parties to a tax allocation agreement with Ameren (parent) that provides for the allocation of consolidated tax liabilities. The tax allocation agreement specifies that each party be allocated an amount of tax similar to that which would be owed or refunded had the party been separately subject to tax. Any net benefit attributable to the parent is reallocated to the other parties. This reallocation is treated as a capital contribution to the party receiving the benefit.
Earnings per Share
Basic earnings per share is computed by dividing net income attributable to Ameren common shareholders by the weighted-average number of common shares outstanding during the period. Earnings per diluted share is computed by dividing net income attributable to Ameren common shareholders by the weighted-average number of diluted common shares outstanding during the period. Earnings per diluted share reflects the potential dilution that would occur if certain stock-based performance share units were settled. The number of performance share units assumed to be settled was 1.0 million, 1.8 million, and 1.9 million for the years ended December 31, 2015, 2014, and 2013, respectively. There were no potentially dilutive securities excluded from the diluted earnings per share calculations for the years ended December 31, 2015, 2014, and 2013.
Capital Contributions and Return of Capital
In 2015, Ameren Missouri and Ameren Illinois received cash capital contributions of $224 million and $25 million, respectively, from Ameren (parent) as a result of the tax allocation agreement. Additionally, as of December 31, 2015, Ameren Missouri accrued a $38 million capital contribution related to the same agreement.
In 2014, Ameren Missouri and Ameren Illinois received cash capital contributions of $215 million and $15 million, respectively, from Ameren (parent) as a result of the tax allocation agreement. Additionally, as of December 31, 2014, Ameren Missouri accrued a $9 million capital contribution related to the same agreement. Also in 2014, Ameren Missouri returned capital of $215 million to Ameren (parent).
Supplemental Cash Flow Information
The following table presents additional information regarding Ameren's consolidated statement of cash flows for the years ended December 31, 2015, 2014, and 2013:
 
2015
 
2014
 
2013
Cash paid (refunded) during the year:
Interest
 
 
 
 
 
Continuing operations(a)
$
335

 
$
333

 
$
362

Discontinued operations(b)
—

 
—

 
31

 
$
335

 
$
333

 
$
393

 
 
 
 
 
 
Income taxes, net
 
 
 
 
 
Continuing Operations
$
(17
)
 
$
(41
)
 
$
116

Discontinued Operations
2

 
14

 
(108
)
 
$
(15
)
 
$
(27
)
 
$
8

(a)
Net of $17 million, $18 million, and $20 million capitalized, respectively.
(b)
Net of $- million, $- million, and $17 million capitalized, respectively.
See Note 3 – Property and Plant, Net, for information on accrued capital expenditures.
Accounting Changes and Other Matters
The following is a summary of recently adopted authoritative accounting guidance, as well as guidance issued but not yet adopted, that could affect the Ameren Companies.
Revenue from Contracts with Customers
In May 2014, the FASB issued authoritative accounting guidance that changes the criteria for recognizing revenue from a contract with a customer. The underlying principle of the guidance is that an entity will recognize revenue for the transfer of promised goods or services to customers at an amount that the entity expects to be entitled to in exchange for those goods or services. The guidance also requires additional disclosures to enable users of financial statements to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. Entities can apply the guidance retrospectively to each reporting period presented or retrospectively by recording a cumulative effect adjustment to retained earnings in the period of initial adoption. The Ameren Companies are currently assessing the impacts of this guidance on their results of operations, financial position, and disclosures, including their accounting for contributions in aid of construction and similar arrangements, as well as the transition method that they will use to adopt the guidance. In August 2015, the FASB deferred the effective date of this revenue guidance to the first quarter of 2018, with an option for entities to early adopt in the first quarter of 2017. The Ameren Companies do not expect to early adopt this guidance.
Amendments to the Consolidation Analysis
In February 2015, the FASB issued authoritative accounting guidance that amends the consolidation analysis for variable interest entities and voting interest entities. The new guidance affects (1) limited partnerships and similar legal entities, (2) evaluating fees paid to a decision maker or service provider as a variable interest, (3) the effect of fee arrangements on the primary beneficiary determination, (4) the effect of related parties on the primary beneficiary determination, and (5) certain investment funds. The guidance is effective for the Ameren Companies in the first quarter of 2016, and can be applied retrospectively to each reporting period presented or retrospectively by recording a cumulative effect adjustment to retained earnings in the period of initial adoption. The Ameren Companies are currently assessing this guidance and do not expect any material impacts to their results of operations, financial position or cash flows.
Presentation of Debt Issuance Costs
In April 2015, the FASB issued authoritative accounting guidance to simplify the presentation of debt issuance costs in the balance sheet. The guidance requires debt issuance costs to be presented as a reduction to the associated debt liability. Previously, debt issuance costs were presented in "Other assets" on the Ameren Companies' balance sheets. The Ameren Companies early adopted this standard in 2015 and applied the guidance retrospectively. At December 31, 2015, debt issuance costs of $43 million, $19 million, and $18 million were presented in "Long-term debt, net" on Ameren's, Ameren Missouri's, and Ameren Illinois' balance sheets, respectively. At December 31, 2014, debt issuance costs of $35 million, $18 million, and $17 million previously presented in "Other assets" on Ameren's, Ameren Missouri's, and Ameren Illinois' respective balance sheets were reclassified to Long-term debt, net" for comparative purposes. See Note 5 – Long-Term Debt and Equity Financings for additional information. The implementation of this authoritative accounting guidance did not affect the Ameren Companies' results of operations or cash flows.
Balance Sheet Classification of Deferred Income Taxes
In November 2015, the FASB issued authoritative accounting guidance to simplify the presentation of deferred income taxes in the balance sheet. The guidance requires all deferred tax assets and liabilities, along with any related valuation allowances, to be classified as noncurrent on the balance sheet. Previously, the current portion of deferred taxes was presented as "Current accumulated deferred income taxes, net" and the noncurrent portion of deferred taxes was presented as "Accumulated deferred income taxes, net" on the Ameren Companies' balance sheets. The Ameren Companies early adopted this standard in 2015 and applied the guidance retrospectively. At December 31, 2014, the current deferred income taxes of $352 million, $49 million, and $160 million, which were previously presented as "Current accumulated deferred income taxes, net" on Ameren's, Ameren Missouri's, and Ameren Illinois' respective balance sheets, were reclassified and presented in "Accumulated deferred income taxes, net" for comparative purposes. The implementation of this authoritative accounting guidance did not affect the Ameren Companies' results of operations or cash flows.
Leases
In February 2016, the FASB issued authoritative accounting guidance that will require an entity to recognize assets and liabilities arising from a lease. Consistent with current GAAP, the recognition, measurement, and presentation of expenses and cash flows arising from a lease will depend primarily on its classification as a finance or operating lease. The guidance also requires additional disclosures to enable users of financial statements to understand the amount, timing, and uncertainty of cash flows arising from leases. The guidance will be effective for the Ameren Companies in the first quarter of 2019, and includes an option for entities to early adopt. The guidance requires a retrospective cumulative adjustment to retained earnings in the period of initial adoption. The Ameren Companies are currently assessing the impacts of this guidance on their results of operations, financial position, cash flows and disclosures.
Rate And Regulatory Matters
RATE AND REGULATORY MATTERS
RATE AND REGULATORY MATTERS
Below is a summary of significant regulatory proceedings and related lawsuits. We are unable to predict the ultimate outcome of these matters, the timing of the final decisions of the various agencies and courts, or the effect on our results of operations, financial position, or liquidity.
Missouri
2015 Electric Rate Order
In April 2015, the MoPSC issued an order approving a $122 million increase in Ameren Missouri’s annual revenues for electric service, including $109 million related to the increase in net energy costs above those included in base rates previously authorized by the MoPSC. The revenue increase was based on a 9.53% return on common equity, a capital structure composed of 51.8% common equity, and a rate base of $7.0 billion to reflect investments through December 31, 2014. Rate changes consistent with the order became effective on May 30, 2015.
The order approved Ameren Missouri’s request for continued use of the FAC; however, it changed the FAC to exclude all transmission revenues and substantially all transmission charges. The order did not approve the continued use of the regulatory tracking mechanisms for storm costs or for vegetation management and infrastructure inspection costs. These changes to Ameren Missouri’s recovery mechanisms are expected to contribute to regulatory lag. The order did approve the continued use of the regulatory tracking mechanisms for pension and other postretirement benefits, renewable energy standard costs, solar rebates, and uncertain tax positions that the MoPSC authorized in prior electric rate orders.
In addition, the order approved a reduction to Noranda’s electric rates with an offsetting increase in electric rates for Ameren Missouri’s other customers. The rate shift is designed to be revenue neutral for Ameren Missouri. In June 2015, Ameren Missouri filed an appeal with the Missouri Court of Appeals, Western District, concerning the reduction to Noranda’s electric rates included in the MoPSC’s order. In February 2016, Ameren Missouri withdrew its appeal.
MEEIA
The MEEIA established a regulatory framework that, among other things, requires the MoPSC to ensure that a utility’s financial incentives are aligned to help customers use energy more efficiently, to provide timely cost recovery, and to provide earnings opportunities associated with cost-effective energy efficiency programs. Missouri does not have a law mandating energy efficiency programs.
In August 2012, the MoPSC approved Ameren Missouri’s customer energy efficiency programs, net shared benefits, and performance incentive for 2013 through 2015. From 2013 through 2015, Ameren Missouri invested $134 million in customer energy efficiency programs and realized $174 million of net shared benefits. The MoPSC also established a performance incentive that would provide Ameren Missouri an opportunity to earn additional revenues by achieving certain customer energy efficiency goals, including $19 million if 100% of the goals were achieved during the three-year period, with the potential to earn a larger performance incentive if Ameren Missouri’s energy savings exceeded those goals.
In June 2015, the MoPSC staff filed a complaint case with the MoPSC regarding the method and inputs used in calculating the performance incentive for 2014 and 2015. In November 2015, the MoPSC issued an order that adopted the MoPSC staff’s method and inputs used in calculating the performance incentive for 2014 and 2015. Ameren Missouri filed an appeal of the order with the Missouri Court of Appeals, Western District. If the Missouri Court of Appeals upholds the MoPSC order, the performance incentive awarded from the 2014 and 2015 MEEIA programs will be significantly less than the performance incentive calculated using Ameren Missouri’s interpretation. Ameren Missouri has not recorded revenues associated with the performance incentive for any of the MEEIA program years. Ameren Missouri believes that it will ultimately be found to have exceeded 100% of the customer energy efficiency goals, and it therefore expects to recognize revenues of at least $19 million in 2016.
In February 2016, the MoPSC issued an order approving Ameren Missouri's March 2016 to February 2019 MEEIA plan which included a portfolio of customer energy efficiency programs along with a rider to collect the program costs, the throughput disincentive, and a performance incentive from customers. The throughput disincentive recovery will replace the net shared benefits that were collected under the 2013 through 2015 MEEIA plan. The MEEIA rider will allow Ameren Missouri to collect the throughput disincentive without a traditional rate proceeding, until such time as lower volumes resulting from the MEEIA programs are reflected in base rates. Customer rates will be based upon both forecasted program costs and throughput disincentive which will be annually reconciled to actual results. Beginning in March 2016, Ameren Missouri intends to invest $158 million over the three-year period in customer energy efficiency programs. In addition, similar to the MEEIA plan that ended in December 2015, the MoPSC's order approved a performance incentive that would provide Ameren Missouri an opportunity to earn additional revenues by achieving certain customer energy efficiency goals, including $27 million if 100% of the goals are achieved during the three-year period, with the potential to earn more if Ameren Missouri's energy savings exceed those goals. Ameren Missouri must achieve at least 25% of its energy efficiency goals before it earns a performance incentive.
Noranda
Ameren Missouri supplies electricity to Noranda’s aluminum smelter located in southeast Missouri under a long-term power supply agreement. In May 2015, Ameren Missouri notified Noranda of its intent to terminate the agreement effective June 1, 2020. If Ameren Missouri wants to cease providing electricity to Noranda following the termination date, Ameren Missouri would also be required to obtain approval from the MoPSC.
On January 8, 2016, Noranda announced that production had been idled at two of its three pot lines at the smelter following an electric supply circuit failure on assets not owned by Ameren Missouri. On January 13, 2016, Noranda announced that the smelter’s “remaining operations will be curtailed on or before March 12, 2016, unless [Noranda] is able to secure a substantially more sustainable power rate for the smelter and materially improve [Noranda’s] overall liquidity.” Ameren Missouri has been working with Noranda, legislators and other stakeholders on a potential legislative solution to support Noranda’s operations.
In its April 2015 electric rate order, the MoPSC approved a rate design that established $78 million in annual revenues, net of fuel and purchased power costs, as Noranda’s portion of Ameren Missouri’s revenue requirement. The portion of Ameren Missouri’s annual revenue requirement reflected in Noranda’s electric rate is based on the smelter using approximately 4.2 million megawatthours annually, which is almost 100% of its operating capacity. Ameren Missouri’s rates, including those for Noranda, are seasonal. Noranda’s summer base rate (June through September) is $45.78 per megawatthour and its winter base rate (October through May) is $31.11 per megawatthour.
In 2016, actual sales volumes to Noranda will be significantly below the sales volumes reflected in rates. As a result, Ameren Missouri will not fully recover its revenue requirement until rates are adjusted by the MoPSC in a future electric rate case to accurately reflect Noranda’s actual sales volumes. In light of the Noranda announcements described above, Ameren Missouri expects to employ a provision in its FAC tariff that, under certain circumstances, allows Ameren Missouri to retain a portion of the revenues from any off-system sales it makes as a result of reduced tariff sales to Noranda. The current market price of electricity is less than Noranda’s electric rate, and Ameren Missouri expects market prices to remain below Noranda’s electric rate during 2016. Accordingly, this FAC provision would not enable Ameren Missouri to fully recover its revenue requirement under current market conditions.
Although Ameren Missouri has not decided when to file its next electric rate case, on January 11, 2016, Ameren Missouri filed a notice with the MoPSC, that would enable Ameren Missouri to file a rate case after 60 days. Ameren Missouri expects to file a rate case in 2016 and expects the resulting new rates to reflect Noranda’s actual sales volumes which would prospectively eliminate the impact of the current revenue shortfall. The rate case would take place over a period of up to 11 months from the date of filing. Ameren Missouri may seek recovery of lost revenues in a filing with the MoPSC for certain costs incurred but not contemporaneously recovered as a result of Noranda's reduced operations. Ameren Missouri will continue to monitor Noranda’s sales volumes and to evaluate regulatory and legislative options that might mitigate adverse financial impacts. The reduction in Noranda’s sales volumes will adversely affect Ameren’s and Ameren Missouri’s results of operations, financial condition, and liquidity until customer rates are adjusted in a future rate case.
On February 8, 2016, Noranda filed voluntary petitions for a court-supervised restructuring process under Chapter 11 of the United States Bankruptcy Code. In the filing, Noranda reaffirmed that the remaining pot line will continue to operate at the smelter until March 2016, at which time operation of the line will be curtailed. Noranda stated it would maintain the flexibility to restart operations at the smelter should conditions allow. For utility service through February 8, 2016, Noranda had prepaid an amount to Ameren Missouri in excess of its utility service usage. Ameren Missouri expects to be paid in full for utility services provided after February 8, 2016.
ATXI Transmission Projects
In May 2015, the MoPSC granted ATXI a certificate of convenience and necessity for the seven-mile portion of the Illinois Rivers project located in Missouri.
In June 2015, ATXI made a filing with the MoPSC requesting a certificate of convenience and necessity for the Mark Twain project. The Mark Twain project is a MISO-approved 100-mile transmission line located in northeast Missouri. A decision is expected from the MoPSC in 2016.
Illinois
IEIMA
Under the provisions of the IEIMA's performance-based formula rate-making framework, which currently extends through 2019, Ameren Illinois’ electric delivery service rates are subject to an annual revenue requirement reconciliation to its actual recoverable costs. Throughout each year, Ameren Illinois records a regulatory asset or a regulatory liability and a corresponding increase or decrease to operating revenues for any differences between the revenue requirement reflected in customer rates for that year and its estimate of the probable increase or decrease in the revenue requirement expected to ultimately be approved by the ICC based on that year's actual recoverable costs incurred. As of December 31, 2015, Ameren Illinois had recorded regulatory assets of $62 million and $103 million, including interest, to reflect its expected 2015 and the 2014 approved revenue requirement reconciliation adjustments, respectively. As of December 31, 2014, Ameren Illinois had recorded a $65 million regulatory asset to reflect its approved 2013 revenue requirement reconciliation adjustment, which was collected, with interest, from customers during 2015.
In December 2015, the ICC issued an order in Ameren Illinois’ annual update filing approving a $106 million increase in Ameren Illinois’ electric delivery service revenue requirement beginning in January 2016. This update reflects an increase to the annual formula rate based on 2014 actual recoverable costs and expected net plant additions for 2015, an increase to include the 2014 revenue requirement reconciliation adjustment, which was recorded as a regulatory asset at December 31, 2015, and a decrease for the conclusion of the 2013 revenue requirement reconciliation adjustment, which was fully collected from customers in 2015.
In December 2013, the ICC issued an order that disallowed, in part, the recovery from customers of the debt premium costs paid by Ameren Illinois for a tender offer in August 2012 to repurchase outstanding senior secured notes. As a result of the ICC order, in 2013, Ameren and Ameren Illinois each recorded a pretax charge to earnings of $15 million relating to the partial disallowance of the debt premium costs. In December 2014, the ICC issued an order that allowed partial recovery from customers of the previously disallowed debt premium costs. Accordingly, in 2014, Ameren and Ameren Illinois each recorded a pretax increase to earnings of $11 million to reflect the partial recovery of the debt premium costs. Ameren and Ameren Illinois recorded the effects of the 2013 and 2014 orders to "Interest charges" with a corresponding offset to "Regulatory assets."
2015 Natural Gas Delivery Service Rate Order
In December 2015, the ICC issued a rate order that approved an increase in revenues for Ameren Illinois' natural gas delivery service of $45 million. The revenue increase was based on a 9.6% return on common equity, a capital structure composed of 50% common equity, and a rate base of $1.2 billion. The rate order was based on a 2016 future test year. The rate changes were in effect in January 2016. In addition, the rate order approved the VBA for residential and small nonresidential customers beginning in 2016.
2015 ICC Purchased Power Reconciliation
In January 2015, the ICC issued an order that approved Ameren Illinois' reconciliation of revenues collected under its purchased power rider mechanism and Ameren Illinois' related cumulative power usage cost. In the first quarter of 2015, based on the January 2015 order, both Ameren and Ameren Illinois recorded a $15 million increase to electric revenues for the recovery of this cumulative power usage cost from electric customers.
ATXI Transmission Project
The Spoon River project is a MISO-approved 46-mile transmission line to be constructed in northwest Illinois. In September 2015, the ICC granted a certificate of public convenience and necessity and project approval for the Spoon River project.
Federal
Ameren Illinois Electric Transmission Rate Refund
In July 2012, the FERC issued an order concluding that Ameren Illinois improperly included acquisition premiums, including goodwill, in determining the common equity used in its electric transmission formula rate and thereby inappropriately recovered a higher amount from its electric transmission customers. The order required Ameren Illinois to make refunds to customers for such improperly included amounts.
In July 2015, the FERC approved a settlement agreement between Ameren Illinois and the affected customers. The settlement agreement required Ameren Illinois to make refunds and payments of $8 million to electric transmission customers, all of which was paid in 2015. The settlement agreement also required Ameren Illinois to take other actions, such as reducing common equity for electric transmission ratemaking purposes on a prospective basis. The transmission rates that became effective on January 1, 2016, reflect these adjustments.
FERC Complaint Cases
In November 2013, a customer group filed a complaint case with the FERC seeking a reduction in the allowed base return on common equity for the FERC-regulated transmission rate base under the MISO tariff from 12.38% to 9.15%. In December 2015, an administrative law judge issued an initial decision in the November 2013 complaint case that would lower the allowed base return on common equity to 10.32% and would require customer refunds to be issued for the 15-month period ending February 2015. The allowed base return on common equity in the initial decision was based on multiple inputs, including observable market data for the six months ended June 30, 2015. The FERC is expected to issue a final order on the November 2013 complaint case by October 2016.
As the maximum FERC-allowed refund period for the November 2013 complaint case ended in February 2015, another customer complaint case was filed in February 2015. The February 2015 complaint case seeks a reduction in the allowed base return on common equity for the FERC-regulated transmission rate base under the MISO tariff to 8.67%. The initial decision from an administrative law judge in the February 2015 complaint case, which will subsequently require FERC approval, is expected to be issued by June 2016.
On January 6, 2015, a FERC-approved incentive adder of up to 50 basis points on the allowed base return on common equity for our participation in an RTO became effective. Beginning with its January 6, 2015 effective date, the incentive adder will reduce any refund to customers relating to a reduction of the allowed base return on common equity from the complaint cases discussed above.
As of December 31, 2015, Ameren and Ameren Illinois had current regulatory liabilities of $45 million and $32 million, respectively, representing their estimates of the potential refunds from the November 12, 2013 refund effective date through December 31, 2015. Ameren and Ameren Illinois recorded liabilities to reflect the allowed base return on common equity in the initial decision for the November 2013 complaint case refund period, and the observable market data for the six months ended December 31, 2015, for the February 2015 complaint case refund period. Ameren’s and Ameren Illinois’ liabilities also reflect the January 6, 2015 incentive adder discussed above. Ameren Missouri did not record a liability as of December 31, 2015, and it does not expect that a reduction in the FERC-allowed base return on common equity for MISO transmission owners would be material to its results of operations, financial position, or liquidity.
Combined Construction and Operating License
In 2008, Ameren Missouri filed an application with the NRC for a COL for a second nuclear unit at Ameren Missouri's existing Callaway County, Missouri, energy center site. In 2009, Ameren Missouri suspended its efforts to build a second nuclear unit at its existing Callaway site, and the NRC suspended review of the COL application. Prior to suspending its efforts, Ameren Missouri had capitalized $69 million related to the project. Primarily because of changes in vendor support for licensing efforts at the NRC, Ameren Missouri’s assessment of long-term capacity needs, declining costs of alternative generation technologies, and the regulatory framework in Missouri, Ameren Missouri discontinued its efforts to license and build a second nuclear unit at its existing Callaway site. As a result of this decision, in the second quarter of 2015, Ameren and Ameren Missouri recognized a $69 million noncash pretax provision for all of the previously capitalized COL costs. Ameren Missouri has withdrawn its COL application with the NRC.
Regulatory Assets and Liabilities
In accordance with authoritative accounting guidance regarding accounting for the effects of certain types of regulation, we defer certain costs as regulatory assets pursuant to actions of regulators or because we expect to recover such costs in rates charged to customers. We may also defer certain amounts as regulatory liabilities because of actions of regulators or because we expect that such amounts will be returned to customers in future rates. The following table presents our regulatory assets and regulatory liabilities at December 31, 2015 and 2014:
 
 
2015
 
2014
 
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
 
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
Current regulatory assets:
 
 
 
 
 
 
 
 
 
 
 
 
 
Under-recovered FAC(a)(b)
 
$
37

 
$
—

 
$
37

 
 
$
128

 
$
—

 
$
128

Under-recovered Illinois electric power costs(c)
 
—

 
3

 
3

 
 
—

 
2

 
2

Under-recovered PGA(c)
 
—

 
8

 
8

 
 
—

 
20

 
20

MTM derivative losses(d)
 
29


45

 
74

 
 
32

 
42

 
74

Energy efficiency riders(e)

 
23

 
—

 
23

 
 
3

 
—

 
3

IEIMA revenue requirement reconciliation adjustment(a)(f)
 
—

 
103

 
103

 
 
—

 
65

 
65

FERC revenue requirement reconciliation adjustment(a)(g)

 
—

 
8

 
12

 
 
—

 
—

 
3

Total current regulatory assets
 
$
89

 
$
167

 
$
260

 
 
$
163

 
$
129

 
$
295

Noncurrent regulatory assets:
 
 
 
 
 
 
 
 
 
 
 
 
 
Pension and postretirement benefit costs(h)
 
$
95

 
$
202

 
$
297

 
 
$
148

 
$
275

 
$
423

Income taxes(i)
 
254

 
4

 
258

 
 
253

 
3

 
256

Asset retirement obligations(j)
 
—

 
4

 
4

 
 
—

 
5

 
5

Callaway costs(a)(k)
 
32

 
—

 
32

 
 
36

 
—

 
36

Unamortized loss on reacquired debt(a)(l)
 
69

 
69

 
138

 
 
72

 
80

 
152

Contaminated facilities costs(m)
 
—

 
230

 
230

 
 
—

 
251

 
251

MTM derivative losses(d)
 
15


175

 
190



14

 
144

 
158

Storm costs(a)(n)
 
—

 
9

 
9

 
 
—

 
3

 
3

Demand-side costs before the MEEIA implementation(a)(o)
 
31

 
—

 
31

 
 
44

 
—

 
44

Workers’ compensation claims(p)
 
6

 
7

 
13

 
 
7

 
7

 
14

Credit facilities fees(q)
 
4

 
—

 
4

 
 
5

 
—

 
5

Construction accounting for pollution control equipment(a)(r)
 
20

 
—

 
20

 
 
21

 
—

 
21

Solar rebate program(a)(s)
 
74

 
—

 
74

 
 
88

 
—

 
88

IEIMA revenue requirement reconciliation adjustment(a)(f)
 
—

 
62

 
62

 
 
—

 
101

 
101

FERC revenue requirement reconciliation adjustment(a)(g)
 
—

 
5

 
11

 
 
—

 
8

 
12

Other
 
5

 
4

 
9

 
 
7

 
6

 
13

Total noncurrent regulatory assets
 
$
605

 
$
771

 
$
1,382

 
 
$
695

 
$
883

 
$
1,582

Current regulatory liabilities:
 
 
 
 
 
 
 
 
 
 
 
 
 
Over-recovered FAC(b)
 
$
9

 
$
—

 
$
9

 
 
$
—

 
$
—

 
$
—

Over-recovered Illinois electric power costs(c)
 
—

 
6

 
6

 
 
—

 
26

 
26

Over-recovered PGA(c)
 
3

 
—

 
3

 
 
2

 
25

 
27

MTM derivative gains(d)
 
16

 
1

 
17


 
16

 
1

 
17

FERC revenue requirement reconciliation adjustment(g)
 
—

 
—

 
—

 
 
—

 
11

 
11

Estimated refund for FERC complaint cases, orders, and audit findings(t)
 
—

 
32

 
45

 
 
—

 
21

 
25

Total current regulatory liabilities
 
$
28

 
$
39

 
$
80

 
 
$
18

 
$
84

 
$
106

Noncurrent regulatory liabilities:
 
 
 
 
 
 
 
 
 
 
 
 
 
Income taxes(u)
 
$
36

 
$
6

 
$
42

 
 
$
41

 
$
14

 
$
55

Uncertain tax positions tracker(v)
 
6

 
—

 
6

 
 
7

 
—

 
7

Removal costs(w)
 
933

 
671

 
1,605

 
 
886

 
643

 
1,529

Asset retirement obligation(j)
 
167

 
—

 
167

 
 
182

 
—

 
182

Bad debt riders(x)
 
—

 
6

 
6

 
 
—

 
7

 
7

Pension and postretirement benefit costs tracker(y)
 
19

 
—

 
19

 
 
24

 
—

 
24

Energy efficiency riders(e)
 
—

 
36

 
36

 
 
—

 
39

 
39

Renewable energy credits(z)
 
—

 
12

 
12

 
 
1

 
—

 
1

Storm tracker(aa)
 
9

 
—

 
9

 
 
6

 
—

 
6

Other
 
2

 
1

 
3

 
 
—

 
—

 
—

Total noncurrent regulatory liabilities
 
$
1,172

 
$
732

 
$
1,905

 
 
$
1,147

 
$
703

 
$
1,850

(a)
These assets earn a return.
(b)
Under-recovered or over-recovered fuel costs to be recovered or refunded through the FAC. Specific accumulation periods aggregate the under-recovered or over-recovered costs over four months, any related adjustments that occur over the following four months, and the recovery from or refund to customers that occurs over the next eight months.
(c)
Under-recovered or over-recovered costs from utility customers. Amounts will be recovered from, or refunded to, customers within one year of the deferral.
(d)
Deferral of commodity-related derivative MTM losses or gains. See Note 7 – Derivative Financial Instruments for additional information.
(e)
The Ameren Missouri balance relates to the MEEIA. Beginning in January 2014, the MEEIA rider allowed Ameren Missouri to collect from or refund to customers any annual difference in the actual amounts incurred and the amounts collected from customers for the MEEIA program costs and its net shared benefits. Under the MEEIA rider, collections from or refunds to customers occur one year after the program costs and lost revenues are incurred. The Ameren Illinois balance relates to a regulatory tracking mechanism to recover its electric and natural gas costs associated with developing, implementing, and evaluating customer energy efficiency and demand response programs. Any under-recovery or over-recovery will be collected from or refunded to customers over the 12 months following the plan year.
(f)
The difference between Ameren Illinois' annual revenue requirement calculated under the IEIMA's performance-based formula ratemaking framework and the revenue requirement included in customer rates for that year. Subject to ICC approval, these amounts will be collected from or refunded to customers with interest within two years.
(g)
Ameren Illinois' and ATXI's annual revenue requirement reconciliation adjustments calculated pursuant to the FERC's electric transmission formula ratemaking framework. The under-recovery or over-recovery will be recovered from or refunded to customers within two years.
(h)
These costs are being amortized in proportion to the recognition of prior service costs (credits) and actuarial losses (gains) attributable to Ameren’s pension plan and postretirement benefit plans. See Note 11 – Retirement Benefits for additional information.
(i)
Tax benefits related to the equity component of allowance for funds used during construction, as well as the effects of tax rate changes. This will be recovered over the expected life of the related assets.
(j)
Recoverable or refundable removal costs for AROs, including net realized and unrealized gains and losses related to the nuclear decommissioning trust fund investments. See Note 1 – Summary of Significant Accounting Policies – Asset Retirement Obligations and Investments.
(k)
Ameren Missouri’s Callaway energy center operations and maintenance expenses, property taxes, and carrying costs incurred between the plant in-service date and the date the plant was reflected in rates. These costs are being amortized over the remaining life of the energy center's original operating license through 2024.
(l)
Losses related to reacquired debt. These amounts are being amortized over the lives of the related new debt issuances or the original lives of the old debt issuances if no new debt was issued.
(m)
The recoverable portion of accrued environmental site liabilities that will be collected from electric and natural gas customers through ICC-approved cost recovery riders. The period of recovery will depend on the timing of remediation expenditures. See Note 15 – Commitments and Contingencies for additional information.
(n)
Storm costs from 2013 and 2015 deferred in accordance with the IEIMA. These costs are being amortized over five-year periods beginning in 2013 and 2015, respectively.
(o)
Demand-side costs incurred prior to implementation of the MEEIA in 2013, including the costs of developing, implementing, and evaluating customer energy efficiency and demand response programs. Costs incurred from May 2008 through September 2008 are being amortized over a 10-year period that began in March 2009. Costs incurred from October 2008 through December 2009 are being amortized until May 2017. Costs incurred from January 2010 through February 2011 are being amortized over a six-year period that began in August 2011. Costs incurred from March 2011 through July 2012 are being amortized over a six-year period that began in January 2013. Costs incurred from August 2012 through December 2012 are being amortized over a six-year period that began in June 2015.
(p)
The period of recovery will depend on the timing of actual expenditures.
(q)
Ameren Missouri’s costs incurred to enter into and maintain the Missouri Credit Agreement. Additional costs were incurred in December 2014 to amend and restate the Missouri Credit Agreement. These costs are being amortized over the life of the credit facility, ending in December 2019, to construction work in progress, which will be depreciated when assets are placed into service.
(r)
The MoPSC’s May 2010 electric rate order allowed Ameren Missouri to record an allowance for funds used during construction for pollution control equipment at its Sioux energy center until the cost of that equipment was included in customer rates beginning in 2011. These costs are being amortized over the expected life of the Sioux energy center, which is currently through 2033.
(s)
Costs associated with Ameren Missouri's solar rebate program beginning in August 2012 to fulfill its renewable energy portfolio requirement. These costs are being amortized over three years, beginning in June 2015.
(t)
Estimated refunds to transmission customers related to FERC orders. See Ameren Illinois Electric Transmission Rate Refund and FERC Complaint Cases above.
(u)
Unamortized portion of investment tax credits and reductions to deferred tax liabilities recorded at rates in excess of current statutory rates. The unamortized portion of investment tax credits and the reduction to deferred tax liabilities are being amortized over the expected life of the underlying assets.
(v)
The tracker is amortized over three years, beginning from the date the amounts are included in rates. See Note 13 – Income Taxes for additional information.
(w)
Estimated funds collected for the eventual dismantling and removal of plant from service, net of salvage value, upon retirement related to our rate-regulated operations.
(x)
A regulatory tracking mechanism for the difference between the level of bad debt incurred by Ameren Illinois under GAAP and the level of such costs included in electric and natural gas rates. The over-recovery relating to 2013 was refunded to customers from June 2014 through May 2015. The over-recovery relating to 2014 will be refunded to customers from June 2015 through May 2016. The over-recovery relating to 2015 will be refunded to customers from June 2016 through May 2017.
(y)
A regulatory tracking mechanism for the difference between the level of pension and postretirement benefit costs incurred by Ameren Missouri under GAAP and the level of such costs included in rates. For periods prior to December 2014, the MoPSC's April 2015 electric rate order directed the amortization to occur over three to five years, beginning in June 2015. For periods after December 2014, the amortization period will be determined in a future electric rate case.
(z)
The Ameren Missouri balance includes the costs of renewable energy credits to fulfill Ameren Missouri's renewable energy portfolio requirement from August 2012 through December 2013, which were less than the amount included in rates. These costs are being amortized over three years beginning in June 2015. The Ameren Illinois balance includes funds collected from customers for the purchase of renewable energy credits through IPA procurements for distributed generation. The balance will be amortized as renewable energy credits are purchased.
(aa)
A regulatory tracking mechanism at Ameren Missouri for the difference between the level of storm costs incurred in a particular year and the level of such costs included in rates. For periods prior to December 2014, the MoPSC's April 2015 electric rate order directed the amortization to occur over five years, beginning in June 2015. For periods after December 2014, the amortization period will be determined in a future electric rate case. The April 2015 MoPSC order did not approve the continued use of the regulatory tracking mechanisms for storm costs.
Ameren, Ameren Missouri, and Ameren Illinois continually assess the recoverability of their regulatory assets. Under current accounting standards, regulatory assets are charged to earnings when it is no longer probable that such amounts will be recovered through future revenues. To the extent that payments of regulatory liabilities are no longer probable, the amounts are credited to earnings.
Property And Plant, Net
PROPERTY AND PLANT, NET
PROPERTY AND PLANT, NET
The following table presents property and plant, net, for each of the Ameren Companies at December 31, 2015 and 2014:
 
 
Ameren
Missouri(a)
 
Ameren
Illinois
 
Other
 
Ameren(a)
2015
 
 
 
 
 
 
 
 
Property and plant, at original cost:
 
 
 
 
 
 
 
 
Electric
 
$
17,521

 
$
7,253

 
$
387

 
$
25,161

Natural gas
 
445

 
1,997

 
—

 
2,442

 
 
17,966

 
9,250

 
387

 
27,603

Less: Accumulated depreciation and amortization
 
7,460

 
2,632

 
255

 
10,347

 
 
10,506

 
6,618

 
132

 
17,256

Construction work in progress:
 
 
 
 
 
 
 
 
Nuclear fuel in process
 
275

 
—

 
—

 
275

Other
 
402

 
230

 
636

 
1,268

Property and plant, net
 
$
11,183

 
$
6,848

 
$
768

 
$
18,799

2014
 
 
 
 
 
 
 
 
Property and plant, at original cost:
 
 
 
 
 
 
 
 
Electric
 
$
17,052

 
$
6,517

 
$
344

 
$
23,913

Natural gas
 
431

 
1,854

 
—

 
2,285

 
 
17,483

 
8,371

 
344

 
26,198

Less: Accumulated depreciation and amortization
 
7,086

 
2,422

 
251

 
9,759

 
 
10,397

 
5,949

 
93

 
16,439

Construction work in progress:
 
 
 
 
 
 
 
 
Nuclear fuel in process
 
209

 
—

 
—

 
209

Other
 
261

 
216

 
299

 
776

Property and plant, net
 
$
10,867

 
$
6,165

 
$
392

 
$
17,424


(a)
Amounts in Ameren and Ameren Missouri include two CTs under separate capital lease agreements. The gross cumulative asset value of those agreements was $233 million at December 31, 2015 and 2014. The total accumulated depreciation associated with the two CTs was $72 million and $66 million at December 31, 2015 and 2014, respectively. In addition, Ameren Missouri has investments in debt securities, which were classified as held-to-maturity and recorded in "Other assets", related to the two CTs from the city of Bowling Green and Audrain County. As of December 31, 2015 and 2014, the carrying value of these debt securities was $288 million and $294 million, respectively.
The following table provides accrued capital and nuclear fuel expenditures at December 31, 2015, 2014, and 2013, which represent noncash investing activity excluded from the accompanying statements of cash flows:
 
Ameren(a)
 
Ameren
Missouri
 
Ameren
Illinois
Accrued capital expenditures:
 
 
 
 
 
2015
$
235

 
$
85

 
$
92

2014
181

 
72

 
59

2013
175

 
74

 
86

Accrued nuclear fuel expenditures:
 
 
 
 
 
2015
16

 
16

 
(b)

2014
13

 
13

 
(b)

2013
8

 
8

 
(b)


(a)
Includes amounts for Ameren registrant and nonregistrant subsidiaries.
(b)
Not applicable.
Short-Term Debt And Liquidity
SHORT-TERM DEBT AND LIQUIDITY
SHORT-TERM DEBT AND LIQUIDITY
The liquidity needs of the Ameren Companies are typically supported through the use of available cash, drawings under committed credit agreements, commercial paper issuances, or in the case of Ameren Missouri and Ameren Illinois, short-term intercompany borrowings.
Credit Agreements
The Credit Agreements provide a total of $2.1 billion of credit through their December 2019 maturity date. The facilities include 24 international, national, and regional lenders, with no single lender providing more than $115 million of credit in aggregate.

The obligations of each borrower under the respective Credit Agreements to which it is a party are several and not joint. Except under limited circumstances relating to expenses and indemnities, the obligations of Ameren Missouri and Ameren Illinois under the respective Credit Agreements are not guaranteed by Ameren or any other subsidiary of Ameren. The following table presents the maximum aggregate amount available to each borrower under each facility which will expire in December 2019 (the amount being each borrower's "Borrowing Sublimit"):
 
 
Missouri Credit Agreement
Illinois
Credit Agreement
Ameren
 
$
700

$
500

Ameren Missouri
 
800

(a)

Ameren Illinois
 
  (a)

800

(a)
Not applicable.
Ameren has the option to seek additional commitments from existing or new lenders to increase the total facility size of the Credit Agreements to a maximum of $1.2 billion for the Missouri Credit Agreement and $1.3 billion for the Illinois Credit Agreement. The principal amount of each revolving loan owed by a borrower under any of the Credit Agreements to which it is a party will be due and payable no later than the maturity date of such Credit Agreement. The principal amount of each revolving loan owed by Ameren Missouri or Ameren Illinois under the applicable Credit Agreement will be due and payable no later than the earlier of the maturity date or 364 days after the date of such loan. The Credit Agreements are currently scheduled to mature in December 2019, but the maturity date may be extended once or twice for additional one-year periods upon mutual consent of the borrowers and lenders.
The obligations of all borrowers under the Credit Agreements are unsecured. Loans are available on a revolving basis under each of the Credit Agreements. Funds borrowed may be repaid and, subject to satisfaction of the conditions to borrowing, reborrowed from time to time. At the election of each borrower, the interest rates on such loans will be the alternate base rate plus the margin applicable to the particular borrower and/or the eurodollar rate plus the margin applicable to the particular borrower. The applicable margins will be determined by the borrower's long-term unsecured credit ratings or, if no such ratings are in effect, the borrower's corporate/issuer ratings then in effect. The borrowers have received commitments from the lenders to issue letters of credit up to $100 million under each of the Credit Agreements. In addition, the issuance of letters of credit is subject to the $2.1 billion overall combined facility borrowing limitations of the Credit Agreements.
The borrowers will use the proceeds from any borrowings under the Credit Agreements for general corporate purposes, including working capital, commercial paper liquidity support, issuance of letters of credit, loan funding under the Ameren money pool arrangements, and other short-term intercompany loan arrangements, or for paying fees and expenses incurred in connection with the Credit Agreements. Both of the Credit Agreements are available to Ameren to support issuances under Ameren's commercial paper program, subject to borrowing sublimits. The Missouri Credit Agreement and the Illinois Credit Agreement are available to support issuances under Ameren (parent)'s, Ameren Missouri's and Ameren Illinois' commercial paper programs, respectively. As of December 31, 2015, based on commercial paper outstanding and letters of credit issued under the Credit Agreements, the aggregate amount of credit capacity available to Ameren (parent), Ameren Missouri, and Ameren Illinois, collectively, was $1.8 billion.
Ameren, Ameren Missouri, and Ameren Illinois did not borrow under the Credit Agreements for the years ended December 31, 2015 and 2014.
Commercial Paper
The following table summarizes the borrowing activity and relevant interest rates under Ameren (parent)'s, Ameren Missouri's and Ameren Illinois' commercial paper programs, for the years ended December 31, 2015 and 2014:
 
 
Ameren (parent)
Ameren Missouri
Ameren Illinois
Ameren Consolidated
2015
 
 
 
 
 
 
Average daily commercial paper outstanding
 
$
721

 
$
42

$
4

$
767

Outstanding borrowings at period-end
 
301

 
—

—

301

Weighted-average interest rate
 
0.57
%
 
0.50
%
0.44
%
0.55
%
Peak commercial paper during period(a)
 
$
874

 
$
294

$
48

$
1,108

Peak interest rate
 
0.91
%
 
0.60
%
0.60
%
0.91
%
2014
 
 
 
 
 
 
Average daily commercial paper outstanding
 
$
423

 
$
110

$
165

$
639

Outstanding borrowings at period-end
 
585

 
97

32

714

Weighted-average interest rate
 
0.36
%
 
0.38
%
0.32
%
0.36
%
Peak commercial paper during period(a)
 
$
625

 
$
495

$
300

$
910

Peak interest rate
 
0.75
%
 
0.70
%
0.60
%
0.75
%
(a)
The timing of peak commercial paper issuances varies by company, and therefore the peak amounts presented by company might not equal the Ameren Consolidated peak commercial paper issuances for the period.

Indebtedness Provisions and Other Covenants
The information below is a summary of the Ameren Companies’ compliance with indebtedness provisions and other covenants.
The Credit Agreements contain conditions for borrowings and issuances of letters of credit. These include the absence of default or unmatured default, material accuracy of representations and warranties (excluding any representation after the closing date as to the absence of material adverse change and material litigation, and the absence of any notice of violation, liability, or requirement under any environmental laws that could have a material adverse effect), and obtainment of required regulatory authorizations. In addition, it is a condition for any Ameren Illinois borrowing that, at the time of and after giving effect to such borrowing, Ameren Illinois not be in violation of any limitation on its ability to incur unsecured indebtedness contained in its articles of incorporation.
The Credit Agreements also contain nonfinancial covenants, including restrictions on the ability to incur liens, to transact with affiliates, to dispose of assets, to make investments in or transfer assets to its affiliates, and to merge with other entities. The Credit Agreements require each of Ameren, Ameren Missouri, and Ameren Illinois to maintain consolidated indebtedness of not more than 65% of its consolidated total capitalization pursuant to a defined calculation set forth in the agreements. As of December 31, 2015, the ratios of consolidated indebtedness to total consolidated capitalization, calculated in accordance with the provisions of the Credit Agreements, were 51%, 49%, and 47%, for Ameren, Ameren Missouri, and Ameren Illinois, respectively. In addition, under the Illinois Credit Agreement and, by virtue of the cross-default provisions of the Missouri Credit Agreement, under the Missouri Credit Agreement, Ameren is required to maintain a ratio of consolidated funds from operations plus interest expense to consolidated interest expense of 2.0 to 1.0. However, the interest coverage requirement applies only at such times as Ameren does not have a senior long-term unsecured credit rating of at least Baa3 from Moody's or BBB- from S&P. As of December 31, 2015, Ameren exceeded the rating requirements; therefore, the interest coverage requirement was not applicable. Any failure by a borrower to satisfy a financial covenant constitutes an immediate default under the applicable Credit Agreement.
The Credit Agreements contain default provisions that apply separately to each borrower; provided, however, that a default of Ameren Missouri or Ameren Illinois under the applicable Credit Agreement is also deemed to constitute a default of Ameren under such agreement. Defaults include a cross-default resulting from a default of such borrower under any other agreement covering outstanding indebtedness of such borrower and certain subsidiaries (other than project finance subsidiaries and nonmaterial subsidiaries) in excess of $75 million in the aggregate (including under the other Credit Agreement). However, under the default provisions of the Credit Agreements, any default of Ameren under any Credit Agreement that results solely from a default of Ameren Missouri or Ameren Illinois thereunder does not result in a cross-default of Ameren under the other Credit Agreement. Further, the Credit Agreement default provisions provide that an Ameren default under any of the Credit Agreements does not constitute a default by Ameren Missouri or Ameren Illinois.
None of the Ameren Companies' credit agreements or financing agreements contain credit rating triggers that would cause a default or acceleration of repayment of outstanding balances. The Ameren Companies were in compliance with the provisions and covenants of their credit agreements at December 31, 2015.
Money Pools
Ameren has money pool agreements with and among its subsidiaries to coordinate and provide for certain short-term cash and working capital requirements.
Ameren Missouri, Ameren Illinois, and ATXI may participate in the utility money pool as both lenders and borrowers. Ameren and Ameren Services may participate in the utility money pool only as lenders. Surplus internal funds are contributed to the money pool from participants. The primary sources of external funds for the utility money pool are the Credit Agreements and the commercial paper programs. The total amount available to the pool participants from the utility money pool at any given time is reduced by the amount of borrowings made by participants, but it is increased to the extent that the pool participants advance surplus funds to the utility money pool or remit funds from other external sources. The availability of funds is also determined by funding requirement limits established by regulatory authorizations. Participants receiving a loan under the money pool agreement must repay the principal amount of such loan, together with accrued interest. The rate of interest depends on the composition of internal and external funds in the utility money pool. The average interest rate for borrowing under the money pool for the year ended December 31, 2015, was 0.11% (2014 – 0.19%).
See Note 14 – Related Party Transactions for the amount of interest income and expense from the money pool arrangements recorded by the Ameren Companies for the years ended December 31, 2015, 2014, and 2013.
Long-Term Debt And Equity Financings
LONG-TERM DEBT AND EQUITY FINANCINGS
LONG-TERM DEBT AND EQUITY FINANCINGS
The following table presents long-term debt outstanding, including maturities due within one year, for the Ameren Companies as of December 31, 2015 and 2014:
 
2015
 
2014
Ameren (Parent):
 
 
 
2.70% Senior unsecured notes due 2020
$
350

 
$
—

3.65% Senior unsecured notes due 2026
350

 
—

Total long-term debt, gross
700

 
—

Less: Unamortized debt issuance costs(a)
(6
)
 
—

Long-term debt, net
$
694

 
$
—

Ameren Missouri:
 
 
 
Senior secured notes:(b)
 
 
 
4.75% Senior secured notes due 2015
—

 
114

5.40% Senior secured notes due 2016
260

 
260

6.40% Senior secured notes due 2017
425

 
425

6.00% Senior secured notes due 2018(c)
179

 
179

5.10% Senior secured notes due 2018
199

 
199

6.70% Senior secured notes due 2019(c)
329

 
329

5.10% Senior secured notes due 2019
244

 
244

5.00% Senior secured notes due 2020
85

 
85

3.50% Senior secured notes due 2024
350

 
350

5.50% Senior secured notes due 2034
184

 
184

5.30% Senior secured notes due 2037
300

 
300

8.45% Senior secured notes due 2039(c)
350

 
350

3.90% Senior secured notes due 2042(c)
485

 
485

3.65% Senior secured notes due 2045
250

 
—

Environmental improvement and pollution control revenue bonds:
 
 
 
1992 Series due 2022(d)(e)
47

 
47

1993 5.45% Series due 2028(f)
(f)

 
(f)

1998 Series A due 2033(d)(e)
60

 
60

1998 Series B due 2033(d)(e)
50

 
50

1998 Series C due 2033(d)(e)
50

 
50

Capital lease obligations:
 
 
 
City of Bowling Green capital lease (Peno Creek CT) due 2022
48

 
54

Audrain County capital lease (Audrain County CT) due 2023
240

 
240

Total long-term debt, gross
4,135

 
4,005

Less: Unamortized discount and premium
(6
)
 
(6
)
Less: Unamortized debt issuance costs(a)
(19
)
 
(18
)
Less: Maturities due within one year
(266
)
 
(120
)
Long-term debt, net
$
3,844

 
$
3,861

 
2015
 
2014
Ameren Illinois:
 
 
 
Senior secured notes:
 
 
 
6.20% Senior secured notes due 2016(g)
$
54

 
$
54

6.25% Senior secured notes due 2016(h)
75

 
75

6.125% Senior secured notes due 2017(h)(i)
250

 
250

6.25% Senior secured notes due 2018(h)(i)
144

 
144

9.75% Senior secured notes due 2018(h)(i)
313

 
313

2.70% Senior secured notes due 2022(h)(i)
400

 
400

3.25% Senior secured notes due 2025(h)
300

 
300

6.125% Senior secured notes due 2028(h)
60

 
60

6.70% Senior secured notes due 2036(h)
61

 
61

6.70% Senior secured notes due 2036(g)
42

 
42

4.80% Senior secured notes due 2043(h)
280

 
280

4.30% Senior secured notes due 2044(h)
250

 
250

4.15% Senior secured notes due 2046(h)
250

 
—

Environmental improvement and pollution control revenue bonds:
 
 
 
5.90% Series 1993 due 2023(j)
(j)

 
(j)

5.70% 1994A Series due 2024(k)
(k)

 
(k)

1993 Series B-1 due 2028(e)(l)
17

 
17

Total long-term debt, gross
2,496

 
2,246

Less: Unamortized discount and premium
(7
)
 
(5
)
Less: Unamortized debt issuance costs(a)
(18
)
 
(17
)
Less: Maturities due within one year
(129
)
 
—

Long-term debt, net
$
2,342

 
$
2,224

Ameren consolidated long-term debt, net
$
6,880

 
$
6,085

(a)
Reflects the adoption of the new authoritative accounting guidance for the presentation of debt issuance costs. See Note 1 – Summary of Significant Accounting Policies for additional information.
(b)
These notes are collaterally secured by first mortgage bonds issued by Ameren Missouri under the Ameren Missouri mortgage indenture. The notes have a fall-away lien provision and will remain secured only as long as any first mortgage bonds issued under the Ameren Missouri mortgage indenture remain outstanding. Redemption, purchase, or maturity of all first mortgage bonds, including first mortgage bonds currently outstanding and any that may be issued in the future, would result in a release of the first mortgage bonds currently securing these notes, at which time these notes would become unsecured obligations. Considering the Ameren Missouri senior secured notes currently outstanding, we do not expect the first mortgage bond lien protection associated with these notes to fall away until 2042.
(c)
Ameren Missouri has agreed that so long as any of the 3.90% senior secured notes due 2042 are outstanding, Ameren Missouri will not permit a release date to occur, and so long as any of the 6.70% senior secured notes due 2019, 6.00% senior secured notes due 2018 and 8.45% senior secured notes due 2039 are outstanding, Ameren Missouri will not optionally redeem, purchase, or otherwise retire in full the outstanding first mortgage bonds not subject to release provisions.
(d)
These bonds are collaterally secured by first mortgage bonds issued by Ameren Missouri under the Ameren Missouri mortgage indenture and have a fall-away lien provision similar to that of Ameren Missouri's senior secured notes. The bonds are also backed by an insurance guarantee policy.
(e)
The interest rates, and the periods during which such rates apply, vary depending on our selection of defined rate modes. Maximum interest rates could reach 18% depending on the series of bonds. The bonds are callable at 100% of par value. The average interest rates for 2015 and 2014 were as follows:
    
 
2015
 
2014
Ameren Missouri 1992 Series due 2022
0.06%
 
0.10%
Ameren Missouri 1998 Series A due 2033
0.24%
 
0.26%
Ameren Missouri 1998 Series B due 2033
0.24%
 
0.27%
Ameren Missouri 1998 Series C due 2033
0.24%
 
0.26%
Ameren Illinois 1993 Series B-1 due 2028
0.49%
 
0.21%

(f)
These bonds are first mortgage bonds issued by Ameren Missouri under the Ameren Missouri mortgage bond indenture and are secured by substantially all Ameren Missouri property and franchises. The bonds are callable at 100% of par value. Less than $1 million principal amount of the bonds remain outstanding.
(g)
These notes are collaterally secured by first mortgage bonds issued by Ameren Illinois under the CILCO mortgage indenture. The notes have a fall-away lien provision, and Ameren Illinois could cause these notes to become unsecured at any time by redeeming the pollution control bonds 5.90% Series 1993 due 2023 (of which less than $1 million remains outstanding).
(h)
These notes are collaterally secured by mortgage bonds issued by Ameren Illinois under the Ameren Illinois mortgage indenture. They are secured by substantially all property of the former IP and CIPS. The notes have a fall-away lien provision and will remain secured only as long as any series of first mortgage bonds issued under the Ameren Illinois mortgage indenture remain outstanding. Redemption, purchase, or maturity of all mortgage bonds, including first mortgage bonds currently outstanding and any that may be issued in the future, would result in a release of the mortgage bonds currently securing these notes, at which time these notes would become unsecured obligations. Considering the Ameren Illinois senior secured notes currently outstanding, we do not expect the mortgage bond lien protection associated with these notes to fall away until 2024.
(i)
Ameren Illinois has agreed that so long as any of the 2.70% senior secured notes due 2022 are outstanding, Ameren Illinois will not permit a release date to occur, and so long as any of the 9.75% senior secured notes due 2018, 6.25% senior secured notes due 2018 and 6.125% senior secured notes due 2017 are outstanding, Ameren Illinois will not optionally redeem, purchase or otherwise retire in full the outstanding first mortgage bonds not subject to release provisions; therefore, a release date will not occur so long as any of these notes remain outstanding.
(j)
These bonds are first mortgage bonds issued by Ameren Illinois under the CILCO mortgage indenture. They are secured by substantially all property of the former CILCO. The bonds are callable at 100% of par value. Less than $1 million principal amount of the bonds remain outstanding.
(k)
These bonds are mortgage bonds issued by Ameren Illinois under the Ameren Illinois mortgage indenture. They are secured by substantially all property of the former IP and CIPS. The bonds are callable at 100% of par value. The bonds are also backed by an insurance guarantee policy. Less than $1 million principal amount of the bonds remains outstanding.
(l)
The bonds are callable at 100% of par value.
The following table presents the aggregate maturities of long-term debt, including current maturities, for the Ameren Companies at December 31, 2015:
 
Ameren
(parent)(a)
 
 Ameren
Missouri(a)
 
 Ameren
Illinois(a)
 
Ameren
Consolidated
2016
$
—

 
$
266

 
$
129

 
$
395

2017
—

 
431

 
250

 
681

2018
—

 
383

 
457

 
840

2019
—

 
581

 
—

 
581

2020
350

 
92

 
—

 
442

Thereafter
350

 
2,382

 
1,660

 
4,392

Total
$
700

 
$
4,135

 
$
2,496

 
$
7,331

(a)
Excludes unamortized discount and premium and debt issuance costs of $6 million, $25 million, and $25 million at Ameren (parent), Ameren Missouri, and Ameren Illinois, respectively.
All classes of Ameren Missouri’s and Ameren Illinois’ preferred stock are entitled to cumulative dividends, have voting rights, and are not subject to mandatory redemption. The preferred stock of Ameren's subsidiaries was included in "Noncontrolling Interests" on Ameren's consolidated balance sheet. The following table presents the outstanding preferred stock of Ameren Missouri and Ameren Illinois, which is redeemable, at the option of the issuer, at the prices shown below as of December 31, 2015 and 2014:
 
 
 
Redemption Price(per share)
 
2015
 
2014
Ameren Missouri:
 
 
 
 
 
 
 
Without par value and stated value of $100 per share, 25 million shares authorized
 
 
 
 
 
 
$3.50 Series
130,000 shares
 
$
110.00

 
$
13

 
$
13

$3.70 Series
40,000 shares
 
104.75

 
4

 
4

$4.00 Series
150,000 shares
 
105.625

 
15

 
15

$4.30 Series
40,000 shares
 
105.00

 
4

 
4

$4.50 Series
213,595 shares
 
110.00

(a) 
21

 
21

$4.56 Series
200,000 shares
 
102.47

 
20

 
20

$4.75 Series
20,000 shares
 
102.176

 
2

 
2

$5.50 Series A
14,000 shares
 
110.00

 
1

 
1

Total
 
 
 
$
80

 
$
80

Ameren Illinois:
 
 
 
 
 
 
 
With par value of $100 per share, 2 million shares authorized
 
 
 
 
 
 
4.00% Series
144,275 shares
 
$
101.00

 
$
14

 
$
14

4.08% Series
45,224 shares
 
103.00

 
5

 
5

4.20% Series
23,655 shares
 
104.00

 
2

 
2

4.25% Series
50,000 shares
 
102.00

 
5

 
5

4.26% Series
16,621 shares
 
103.00

 
2

 
2

4.42% Series
16,190 shares
 
103.00

 
2

 
2

4.70% Series
18,429 shares
 
103.00

 
2

 
2

4.90% Series
73,825 shares
 
102.00

 
7

 
7

4.92% Series
49,289 shares
 
103.50

 
5

 
5

5.16% Series
50,000 shares
 
102.00

 
5

 
5

6.625% Series
124,274 shares
 
100.00

 
12

 
12

7.75% Series
4,542 shares
 
100.00

 
1

 
1

Total
 
 
 
$
62

 
$
62

Total Ameren
 
 
 
$
142

 
$
142

(a)
In the event of voluntary liquidation, $105.50.
Ameren has 100 million shares of $0.01 par value preferred stock authorized, with no such shares outstanding. Ameren Missouri has 7.5 million shares of $1 par value preference stock authorized, with no such shares outstanding. Ameren Illinois has 2.6 million shares of no par value preferred stock authorized, with no such shares outstanding.
Ameren
In November 2015, Ameren (parent) issued $350 million of 2.70% senior unsecured notes due November 15, 2020, with interest payable semiannually on May 15 and November 15 of each year, beginning May 15, 2016. Ameren (parent) received proceeds of $348 million, which were used to repay a portion of short-term debt.
In November 2015, Ameren (parent) issued $350 million of 3.65% senior unsecured notes due February 15, 2026, with interest payable semiannually on February 15 and August 15 of each year, beginning February 15, 2016. Ameren (parent) received proceeds of $347 million, which were used to repay a portion of short-term debt.
In May 2014, Ameren (parent) repaid at maturity $425 million of its 8.875% senior unsecured notes, plus accrued interest. The notes were repaid with proceeds from commercial paper issuances.
In June 2015, Ameren, Ameren Missouri, and Ameren Illinois filed a Form S-3 shelf registration statement registering the issuance of an indeterminate amount of certain types of securities. The registration statement became effective immediately upon filing and will expire in June 2018.
Ameren filed a Form S-3 registration statement with the SEC in May 2014, authorizing the offering of 8.6 million additional shares of its common stock under DRPlus, which expires in May 2017. Shares of common stock sold under DRPlus are, at Ameren’s option, newly issued shares, treasury shares, or shares purchased in the open market or in privately negotiated transactions.
In October 2013, Ameren filed a Form S-8 registration statement with the SEC, authorizing the offering of 4 million additional shares of its common stock under its 401(k) plan. Shares of common stock sold under the 401(k) plan are, at Ameren’s option, newly issued shares, treasury shares, or shares purchased in the open market or in privately negotiated transactions.
From 2013 through 2015, Ameren shares for its DRPlus and its 401(k) plans were purchased in the open market.
Ameren Missouri
In February 2016, $260 million principal amount of Ameren Missouri's 5.40% senior secured notes matured and were repaid with cash on hand and commercial paper borrowings.
In April 2015, Ameren Missouri issued $250 million of 3.65% senior secured notes due April 15, 2045, with interest payable semiannually on April 15 and October 15 of each year, beginning October 15, 2015. Ameren Missouri received proceeds of $247 million, which were used to repay outstanding short-term debt, including short-term debt that Ameren Missouri incurred in connection with the repayment of $114 million of its 4.75% senior secured notes that matured on April 1, 2015.
In April 2014, Ameren Missouri issued $350 million of 3.50% senior secured notes due April 15, 2024, with interest payable semiannually on April 15 and October 15 of each year, beginning October 15, 2014. Ameren Missouri received proceeds of $348 million, which were used to repay at maturity $104 million of its 5.50% senior secured notes due May 15, 2014 and to repay a portion of its short-term debt.
For information on Ameren Missouri's capital contributions and return of capital, refer to Capital Contributions and Return of Capital in Note 1 – Summary of Significant Accounting Policies.
Ameren Illinois
In December 2015, Ameren Illinois issued $250 million of 4.15% senior secured notes due March 15, 2046, with interest payable semiannually on March 15 and September 15, beginning March 15, 2016. Ameren Illinois received proceeds of $245 million, which were used to repay a portion of its short-term debt.
In January 2014, Ameren Illinois redeemed the following environmental improvement and pollution control revenue bonds at par value plus accrued interest:
Senior Secured Notes
Principal Amount
5.90% Series 1993 due 2023(a)
$
32

5.70% 1994A Series due 2024(a)
36

1993 Series C-1 5.95% due 2026
35

1993 Series C-2 5.70% due 2026
8

5.40% 1998A Series due 2028
19

5.40% 1998B Series due 2028
33

Total amount redeemed
$
163

(a)
Less than $1 million principal amount of the bonds remains outstanding after redemption.
In June 2014, Ameren Illinois issued $250 million of 4.30% senior secured notes due July 1, 2044, with interest payable semiannually on January 1 and July 1, beginning January 1, 2015. Ameren Illinois received proceeds of $246 million, which were used to repay a portion of its short-term debt.
In December 2014, Ameren Illinois issued $300 million of 3.25% senior secured notes due March 1, 2025, with interest payable semiannually on March 1 and September 1, beginning March 1, 2015. Ameren Illinois received proceeds of $298 million, which were used to repay a portion of its short-term debt.
For information on Ameren Illinois' capital contributions, refer to Capital Contributions and Return of Capital in Note 1 – Summary of Significant Accounting Policies.
Indenture Provisions and Other Covenants
Ameren Missouri’s and Ameren Illinois’ indentures, credit facilities, and articles of incorporation include covenants and provisions related to issuances of first mortgage bonds and preferred stock. Ameren Missouri and Ameren Illinois are required to meet certain ratios to issue additional first mortgage bonds and preferred stock. A failure to achieve these ratios would not result in a default under these covenants and provisions but would restrict the companies’ ability to issue bonds or preferred stock. The following table summarizes the required and actual interest coverage ratios for interest charges, dividend coverage ratios, and bonds and preferred stock issuable as of December 31, 2015, at an assumed interest rate of 5% and dividend rate of 6%.
 
Required Interest
Coverage Ratio(a)
Actual Interest
Coverage Ratio
Bonds Issuable(b)
 
Required Dividend
Coverage Ratio(c)
Actual Dividend
Coverage Ratio
Preferred Stock
Issuable
 
Ameren Missouri
>2.0
3.8

$
3,385

  
>2.5
104.0

$
2,315

 
Ameren Illinois
>2.0
6.3

3,566

(d) 
>1.5
2.6

203

(e) 
(a)
Coverage required on the annual interest charges on first mortgage bonds outstanding and to be issued. Coverage is not required in certain cases when additional first mortgage bonds are issued on the basis of retired bonds.
(b)
Amount of bonds issuable based either on required coverage ratios or unfunded property additions, whichever is more restrictive. The amounts shown also include bonds issuable based on retired bond capacity of $946 million and $204 million at Ameren Missouri and Ameren Illinois, respectively.
(c)
Coverage required on the annual dividend on preferred stock outstanding and to be issued, as required in the respective company’s articles of incorporation.
(d)
Amount of bonds issuable by Ameren Illinois based on unfunded property additions and retired bonds solely under the former IP mortgage indenture. The amount of bonds issuable by Ameren Illinois is also subject to the lien restrictions contained in the Illinois Credit Agreement.
(e)
Preferred stock issuable is restricted by the amount of preferred stock that is currently authorized by Ameren Illinois' articles of incorporation.

Ameren's indenture does not require Ameren to comply with any quantitative financial covenants. The indenture does, however, include certain cross-default provisions. Specifically, either (1) the failure by Ameren to pay when due and upon expiration of any applicable grace period any portion of any Ameren indebtedness in excess of $25 million, or (2) the acceleration upon default of the maturity of any Ameren indebtedness in excess of $25 million under any indebtedness agreement, including borrowings under the Credit Agreements or the Ameren commercial paper program, constitutes a default under the indenture, unless such past due or accelerated debt is discharged or the acceleration is rescinded or annulled within a specified period.

Ameren Missouri and Ameren Illinois and certain other nonregistrant Ameren subsidiaries are subject to Section 305(a) of the Federal Power Act, which makes it unlawful for any officer or director of a public utility, as defined in the Federal Power Act, to participate in the making or paying of any dividend from any funds “properly included in capital account.” The FERC has consistently interpreted the provision to allow dividends to be paid as long as (1) the source of the dividends is clearly disclosed, (2) the dividends are not excessive, and (3) there is no self-dealing on the part of corporate officials. At a minimum, Ameren believes that dividends can be paid by its subsidiaries that are public utilities from net income and retained earnings. In addition, under Illinois law, Ameren Illinois may not pay any dividend on its stock unless, among other things, its earnings and earned surplus are sufficient to declare and pay a dividend after provision is made for reasonable and proper reserves, or unless Ameren Illinois has specific authorization from the ICC.
Ameren Illinois’ articles of incorporation require dividend payments on its common stock to be based on ratios of common stock to total capitalization and other provisions related to certain operating expenses and accumulations of earned surplus. Ameren Illinois has made a commitment to the FERC to maintain a minimum 30% ratio of common stock equity to total capitalization. As of December 31, 2015, Ameren Illinois’ ratio of common stock equity to total capitalization was 51%.
In order for the Ameren Companies to issue securities in the future, they will have to comply with all applicable requirements in effect at the time of any such issuances.
Off-Balance-Sheet Arrangements
At December 31, 2015, none of the Ameren Companies had off-balance-sheet financing arrangements, other than operating leases entered into in the ordinary course of business, letters of credit, and Ameren parent guarantee arrangements on behalf of its subsidiaries. None of the Ameren Companies expect to engage in any significant off-balance-sheet financing arrangements in the near future.
Other Income And Expenses
OTHER INCOME AND EXPENSES
OTHER INCOME AND EXPENSES
The following table presents the components of "Other Income and Expenses" in the Ameren Companies’ statements of income (loss) for the years ended December 31, 2015, 2014, and 2013:
 
2015
 
2014
 
2013
 
Ameren:(a)
 
 
 
 
 
 
Miscellaneous income:
 
 
 
 
 
 
Allowance for equity funds used during construction
$
30

 
$
34

 
$
37

 
Interest income on industrial development revenue bonds
27

 
27

 
27

 
Interest income (b)
14

  
10

  
3

 
Other
3

 
8

(c) 
2

 
Total miscellaneous income
$
74

 
$
79

 
$
69

 
Miscellaneous expense:
 
 
 
 
 
 
Donations
$
15

 
$
10

 
$
12

 
Other
15

 
12

 
14

 
Total miscellaneous expense
$
30

 
$
22

 
$
26

 
Ameren Missouri:
 
 
 
 
 
 
Miscellaneous income:
 
 
 
 
 
 
Allowance for equity funds used during construction
$
22

 
$
32

 
$
31

 
Interest income on industrial development revenue bonds
27

 
27

 
27

 
Interest income
1

 
1

 
—

 
Other
2

 
—

 
—

 
Total miscellaneous income
$
52

 
$
60

 
$
58

 
Miscellaneous expense:
 
 
 
 
 
 
Donations
$
5

 
$
6

 
$
4

 
Other
6

 
6

 
7

 
Total miscellaneous expense
$
11

 
$
12

 
$
11

 
Ameren Illinois:
 
 
 
 
 
 
Miscellaneous income:
 
 
 
 
 
 
Allowance for equity funds used during construction
$
8

 
$
2

 
$
6

 
Interest income (b)
12

  
7

  
2

 
Other
1

 
8

(c) 
2

 
Total miscellaneous income
$
21

 
$
17

 
$
10

 
Miscellaneous expense:
 
 
 
 
 
 
Donations
$
5

 
$
4

 
$
4

 
Other
7

 
4

 
5

 
Total miscellaneous expense
$
12

 
$
8

 
$
9

 
(a)
Includes amounts for Ameren registrant and nonregistrant subsidiaries and intercompany eliminations.
(b)
Includes Ameren Illinois' interest income on the IEIMA revenue requirement reconciliation adjustment regulatory assets.
(c)
Includes Ameren Illinois' income earned in 2014 from customer-requested construction.
Derivative Financial Instruments
DERIVATIVE FINANCIAL INSTRUMENTS
DERIVATIVE FINANCIAL INSTRUMENTS
We use derivatives to manage the risk of changes in market prices for natural gas, power, and uranium, as well as the risk of changes in rail transportation surcharges through fuel oil hedges. Such price fluctuations may cause the following:
•
an unrealized appreciation or depreciation of our contracted commitments to purchase or sell when purchase or sale prices under the commitments are compared with current commodity prices;
•
market values of natural gas and uranium inventories that differ from the cost of those commodities in inventory; and
•
actual cash outlays for the purchase of these commodities that differ from anticipated cash outlays.
The derivatives that we use to hedge these risks are governed by our risk management policies for forward contracts, futures, options, and swaps. Our net positions are continually assessed within our structured hedging programs to determine whether new or offsetting transactions are required. The goal of the hedging program is generally to mitigate financial risks while ensuring that sufficient volumes are available to meet our requirements. Contracts we enter into as part of our risk management program may be settled financially, settled by physical delivery, or net settled with the counterparty.
The following table presents open gross commodity contract volumes by commodity type for derivative assets and liabilities as of December 31, 2015 and 2014. As of December 31, 2015, these contracts ran through October 2018, March 2021, May 2032, and January 2019 for fuel oils, natural gas, power, and uranium, respectively.
  
Quantity (in millions, except as indicated)
 
2015
2014
Commodity
Ameren Missouri
Ameren Illinois
Ameren
Ameren Missouri
Ameren Illinois
Ameren
Fuel oils (in gallons)(a)
35
(b)
35
50
(b)
50
Natural gas (in mmbtu)
30
151
181
28
108
136
Power (in megawatthours)
1
10
11
1
11
12
Uranium (pounds in thousands)
494
(b)
494
332
(b)
332

(a)
Fuel oils consist of heating oil and ultra-low-sulfur diesel.
(b)
Not applicable.
Authoritative accounting guidance regarding derivative instruments requires that all contracts considered to be derivative instruments be recorded on the balance sheet at their fair values, unless the NPNS exception applies. See Note 8 – Fair Value Measurements for discussion of our methods of assessing the fair value of derivative instruments. Many of our physical contracts, such as our purchased power contracts, qualify for the NPNS exception to derivative accounting rules. The revenue or expense on NPNS contracts is recognized at the contract price upon physical delivery.
If we determine that a contract meets the definition of a derivative and is not eligible for the NPNS exception, we review the contract to determine whether it qualifies for hedge accounting. We also consider whether gains or losses resulting from such derivatives qualify for regulatory deferral. Derivative contracts that qualify for regulatory deferral are recorded at fair value, with changes in fair value recorded as regulatory assets or regulatory liabilities in the period in which the change occurs. We believe derivative losses and gains deferred as regulatory assets and regulatory liabilities are probable of recovery or refund through future rates charged to customers. Regulatory assets and regulatory liabilities are amortized to operating income as related losses and gains are reflected in rates charged to customers. Therefore, gains and losses on these derivatives have no effect on operating income. As of December 31, 2015 and 2014, all contracts that qualify for hedge accounting receive regulatory deferral.
Authoritative accounting guidance permits companies to offset fair value amounts recognized for the right to reclaim cash collateral (a receivable) or the obligation to return cash collateral (a liability) against fair value amounts recognized for derivative instruments that are executed with the same counterparty under a master netting arrangement or similar agreement. The Ameren Companies did not elect to adopt this guidance for any eligible derivative instruments.
The following table presents the carrying value and balance sheet location of all derivative commodity contracts, none of which were designated as hedging instruments, as of December 31, 2015 and 2014:
 
Balance Sheet Location
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
2015
 
 
 
 
 
 
 
Natural gas
Other current assets
$
—

$
1

$
1

 
Other assets
 
1

 
—

 
1

Power
Other current assets
 
16

 
—

 
16

 
Total assets (a)
$
17

$
1

$
18

Fuel oils
Other current liabilities
$
22

$
—

$
22

 
Other deferred credits and liabilities
 
7

 
—

 
7

Natural gas
MTM derivative liabilities
 
(b)

 
32

 
(b)

 
Other current liabilities
 
6

 
—

 
38

 
Other deferred credits and liabilities
 
8

 
18

 
26

Power
MTM derivative liabilities
 
(b)

 
13

 
(b)

 
Other current liabilities
 
—

 
—

 
13

 
Other deferred credits and liabilities
 
—

 
157

 
157

Uranium
Other current liabilities
 
1

 
—

 
1

 
Total liabilities (c)
$
44

$
220

$
264

2014
 
 
 
 
 
 
 
Fuel oils
Other current assets
$
2

$
—

$
2

Natural gas
Other current assets
 
1

 
1

 
2

Power
Other current assets
 
15

 
—

 
15

 
Total assets (a)
$
18

$
1

$
19

Fuel oils
Other current liabilities
$
22

$
—

$
22

 
Other deferred credits and liabilities
 
7

 
—

 
7

Natural gas
MTM derivative liabilities
 
(b)

 
31

 
(b)

 
Other current liabilities
 
6

 
—

 
37

 
Other deferred credits and liabilities
 
6

 
13

 
19

Power
MTM derivative liabilities
 
(b)

 
11

 
(b)

 
Other current liabilities
 
3

 
—

 
14

 
Other deferred credits and liabilities
 
—

 
131

 
131

Uranium
Other current liabilities
 
2

 
—

 
2

 
Total liabilities (c)
$
46

$
186

$
232

(a)
Because all contracts qualifying for hedge accounting receive regulatory deferral, the cumulative amount of pretax net gains on all derivative instruments is deferred as a regulatory liability.
(b)
Balance sheet line item not applicable to registrant.
(c)
Because all contracts qualifying for hedge accounting receive regulatory deferral, the cumulative amount of pretax net losses on all derivative instruments is deferred as a regulatory asset.
Derivative instruments are subject to various credit-related losses in the event of nonperformance by counterparties to the transaction. Exchange-traded contracts are supported by the financial and credit quality of the clearing members of the respective exchanges and have nominal credit risk. In all other transactions, we are exposed to credit risk. Our credit risk management program involves establishing credit limits and collateral requirements for counterparties, using master netting arrangements or similar agreements, and reporting daily exposure to senior management.
We believe that entering into master netting arrangements or similar agreements mitigates the level of financial loss that could result from default by allowing net settlement of derivative assets and liabilities. We generally enter into the following master netting arrangements: (1) the International Swaps and Derivatives Association Agreement, a standardized financial natural gas and electric contract; (2) the Master Power Purchase and Sale Agreement, created by the Edison Electric Institute and the National Energy Marketers Association, a standardized contract for the purchase and sale of wholesale power; and (3) the North American Energy Standards Board Inc. Agreement, a standardized contract for the purchase and sale of natural gas. These master netting arrangements allow the counterparties to net settle sale and purchase transactions. Further, collateral requirements are calculated at the master netting arrangement or similar agreement level by counterparty.
The following table provides the recognized gross derivative balances and the net amounts of those derivatives subject to an enforceable master netting arrangement or similar agreement as of December 31, 2015 and 2014:
 
 
 
 
Gross Amounts Not Offset on the Balance Sheet
 
 
Commodity Contracts Eligible to be Offset
 
Gross Amounts Recognized on the Balance Sheet
 
Derivative Instruments
 
Cash Collateral Received/Posted(a)
 
Net
Amount
2015
 
 
 
 
 
 
 
 
Assets:
 
 
 
 
 
 
 
 
Ameren Missouri
$
17

$
1

$
—

$
16

Ameren Illinois
 
1

 
—

 
—

 
1

Ameren
$
18

$
1

$
—

$
17

Liabilities:
 
 
 
 
 
 
 
 
Ameren Missouri
$
44

$
1

$
8

$
35

Ameren Illinois
 
220

 
—

 
3

 
217

Ameren
$
264

$
1

$
11

$
252

2014
 
 
 
 
 
 
 
 
Assets:
 
 
 
 
 
 
 
 
Ameren Missouri
$
18

$
5

$
—

$
13

Ameren Illinois
 
1

 
—

 
—

 
1

Ameren
$
19

$
5

$
—

$
14

Liabilities:
 
 
 
 
 
 
 
 
Ameren Missouri
$
46

$
5

$
5

$
36

Ameren Illinois
 
186

 
—

 
—

 
186

Ameren
$
232

$
5

$
5

$
222

(a)
Cash collateral received reduces gross asset balances and is included in “Other current liabilities” and “Other deferred credits and liabilities” on the balance sheet. Cash collateral posted reduces gross liability balances and is included in “Other current assets” and “Other assets” on the balance sheet.
Concentrations of Credit Risk
In determining our concentrations of credit risk related to derivative instruments, we review our individual counterparties and categorize each counterparty into groupings according to the primary business in which each engages. We calculate maximum exposures based on the gross fair value of financial instruments, including NPNS and other accrual contracts. These exposures are presented on a gross basis, which include affiliate exposure not eliminated at the consolidated Ameren level. The potential loss on counterparty exposures may be reduced or eliminated by the application of master netting arrangements or similar agreements and collateral held. As of December 31, 2015, if counterparty groups were to fail completely to perform on contracts, Ameren's, Ameren Missouri's, and Ameren Illinois' maximum exposure would have been immaterial with or without consideration of the application of master netting arrangements or similar agreements and collateral held.
Derivative Instruments with Credit Risk-Related Contingent Features
Our commodity contracts contain collateral provisions tied to the Ameren Companies’ credit ratings. If we were to experience an adverse change in our credit ratings, or if a counterparty with reasonable grounds for uncertainty regarding performance of an obligation requested adequate assurance of performance, additional collateral postings might be required. The following table presents, as of December 31, 2015, the aggregate fair value of all derivative instruments with credit risk-related contingent features in a gross liability position, the cash collateral posted, and the aggregate amount of additional collateral that counterparties could require. The additional collateral required is the net liability position allowed under the master netting arrangements or similar agreements assuming (1) the credit risk-related contingent features underlying these arrangements were triggered on December 31, 2015, and (2) those counterparties with rights to do so requested collateral.
 
Aggregate Fair Value of
Derivative Liabilities(a)
 
Cash
Collateral Posted
 
Potential Aggregate Amount of
Additional Collateral Required(b)
2015
 
 
 
 
 
Ameren Missouri
$
87

 
$
9

 
$
72

Ameren Illinois
78

 
3

 
71

Ameren
$
165

 
$
12

 
$
143

(a)
Before consideration of master netting arrangements or similar agreements and including NPNS and other accrual contract exposures.
(b)
As collateral requirements with certain counterparties are based on master netting arrangements or similar agreements, the aggregate amount of additional collateral required to be posted is determined after consideration of the effects of such arrangements.
Fair Value Measurements
FAIR VALUE MEASUREMENTS
FAIR VALUE MEASUREMENTS
Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. We use various methods to determine fair value, including market, income, and cost approaches. With these approaches, we adopt certain assumptions that market participants would use in pricing the asset or liability, including assumptions about market risk or the risks inherent in the inputs to the valuation. Inputs to valuation can be readily observable, market-corroborated, or unobservable. We use valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs. Authoritative accounting guidance established a fair value hierarchy that prioritizes the inputs used to measure fair value. All financial assets and liabilities carried at fair value are classified and disclosed in one of the following three hierarchy levels:
Level 1: Inputs based on quoted prices in active markets for identical assets or liabilities. Level 1 assets and liabilities are primarily exchange-traded derivatives and assets, including cash and cash equivalents and listed equity securities, such as those held in Ameren Missouri’s nuclear decommissioning trust fund.
The market approach is used to measure the fair value of equity securities held in Ameren Missouri's nuclear decommissioning trust fund. Equity securities in this fund are representative of the S&P 500 index, excluding securities of Ameren Corporation, owners and/or operators of nuclear power plants, and the trustee and investment managers. The S&P 500 index comprises stocks of large-capitalization companies.
Level 2: Market-based inputs corroborated by third-party brokers or exchanges based on transacted market data. Level 2 assets and liabilities include certain assets held in Ameren Missouri’s nuclear decommissioning trust fund, including corporate bonds and other fixed-income securities, United States Treasury and agency securities, and certain over-the-counter derivative instruments, including natural gas and financial power transactions.
Fixed income securities are valued by using prices from independent industry recognized data vendors who provide values that are either exchange-based or matrix-based. The fair value measurements of fixed income securities classified as Level 2 are based on inputs other than quoted prices that are observable for the asset or liability. Examples are matrix pricing, market corroborated pricing, and inputs such as yield curves and indices. Level 2 fixed income securities in the nuclear decommissioning trust fund are primarily corporate bonds, asset-backed securities, and United States agency bonds.
Derivative instruments classified as Level 2 are valued by corroborated observable inputs, such as pricing services or prices from similar instruments that trade in liquid markets. Our development and corroboration process entails obtaining multiple quotes or prices from outside sources. To derive our forward view to price our derivative instruments at fair value, we average the midpoints of the bid/ask spreads. To validate forward prices obtained from outside parties, we compare the pricing to recently settled market transactions. Additionally, a review of all sources is performed to identify any anomalies or potential errors. Further, we consider the volume of transactions on certain trading platforms in our reasonableness assessment of the averaged midpoint. The value of natural gas derivative contracts is based upon exchange closing prices without significant unobservable adjustments. The value of power derivatives contracts is based upon the use of multiple forward prices provided by third parties. The prices are averaged and shaped to a monthly profile when needed without significant unobservable adjustments.
Level 3: Unobservable inputs that are not corroborated by market data. Level 3 assets and liabilities are valued by internally developed models and assumptions or methodologies that use significant unobservable inputs. Level 3 assets and liabilities include derivative instruments that trade in less liquid markets, where pricing is largely unobservable. We value Level 3 instruments by using pricing models with inputs that are often unobservable in the market, as well as certain internal assumptions. Our development and corroboration process entails obtaining multiple quotes or prices from outside sources. As a part of our reasonableness review, an evaluation of all sources is performed to identify any anomalies or potential errors.
We perform an analysis each quarter to determine the appropriate hierarchy level of the assets and liabilities subject to fair value measurements. Financial assets and liabilities are classified in their entirety according to the lowest level of input that is significant to the fair value measurement. All assets and liabilities whose fair value measurement is based on significant unobservable inputs are classified as Level 3.
The following table describes the valuation techniques and unobservable inputs utilized by the Ameren Companies for the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the periods ended December 31, 2015 and 2014:
 
 
Fair Value
 
 
 
 
Weighted
 
 
Assets
Liabilities
 
Valuation Technique(s)
Unobservable Input
Range
Average
 
Level 3 Derivative asset and liability – commodity contracts(a):
 
 
 
2015
 
 
 
 
 
 
 
 
 
Natural Gas
$
1

$
(1
)
 
Option model
Volatilities(%)(b)
35 – 55
45
 



 

Nodal basis($/mmbtu)(c)
(0.30) – 0
(0.20)
 



 
Discounted cash flow
Nodal basis($/mmbtu)(b)
(0.10) – 0
(0.10)
 
 
Fair Value
 
 
 
 
Weighted
 
 
Assets
Liabilities
 
Valuation Technique(s)
Unobservable Input
Range
Average
 



 

Counterparty credit risk(%)(c)(d)
0.40 – 12
7
 



 

Ameren Missouri credit risk(%)(c)(d)
0.40
(e)
 
Power(f)
16

(170
)
 
Discounted cash flow
Average forward peak and off-peak pricing – forwards/swaps($/MWh)(g)
22 – 39
29
 
 
 
 
 
 
Estimated auction price for FTRs($/MW)(b)
(270) – 2,057
211
 
 
 
 
 
 
Nodal basis($/MWh)(g)
(10) – (1)
(3)
 
 
 
 
 
 
Counterparty credit risk(%)(c)(d)
0.86
(e)
 
 
 
 
 
 
Ameren Illinois credit risk(%)(c)(d)
0.40
(e)
 
 
 
 
 
Fundamental energy production model
Estimated future gas prices($/mmbtu)(b)
3 – 4
4
 
 
 
 
 
 
Escalation rate(%)(b)(h)
3
(e)
 
 
 
 
 
Contract price allocation
Estimated renewable energy credit costs($/credit)(b)
5 – 7
6
 
Uranium
—

(1
)
 
Option model
Volatilities(%)(b)
20
(e)
 
 
 
 
 
Discounted cash flow
Average forward uranium pricing($/pound)(b)
35 – 42
37
 
 
 
 
 
 
Ameren Missouri credit risk(%)(c)(d)
0.40
(e)
2014
 
 
 
 
 
 
 
 
 
Fuel oils
$
2

$
(8
)
 
Option model
Volatilities(%)(c)
3 – 39
32
 
 
 
 
 
Discounted cash flow
Ameren Missouri credit risk(%)(c)(d)
0.43
(e)
 
 
 
 
 
 
Escalation rate(%)(b)(i)
5
(e)
 
Natural Gas
1

(2
)
 
Option model
Volatilities(%)(c)
31 – 144
63
 
 
 
 
 
 
Nodal basis($/mmbtu)(b)
(0.40) – 0
(0.20)
 
 
 
 
 
Discounted cash flow
Nodal basis($/mmbtu)(b)
(0.40) – 0.10
(0.20)
 
 
 
 
 
 
Counterparty credit risk(%)(c)(d)
0.43 – 13
3
 
 
 
 
 
 
Ameren Missouri and Ameren Illinois credit risk(%)(c)(d)
0.43
(e)
 
Power(f)
11

(144
)
 
Discounted cash flow
Average forward peak and off-peak pricing – forwards/swaps($/MWh)(g)
27 – 50
32
 
 
 
 
 
 
Estimated auction price for FTRs($/MW)(b)
(1,833) – 2,743
171
 
 
 
 
 
 
Nodal basis($/MWh)(b)
(6) – 0
(2)
 
 
 
 
 
 
Counterparty credit risk(%)(c)(d)
0.26
(e)
 
 
 
 
 
 
Ameren Missouri and Ameren Illinois credit risk(%)(c)(d)
0.43
(e)
 
 
 
 
 
Fundamental energy production model
Estimated future gas prices($/mmbtu)(b)
4 – 5
4
 
 
 
 
 
 
Escalation rate(%)(b)(h)
0 – 1
1
 
 
 
 
 
Contract price allocation
Estimated renewable energy credit costs($/credit)(b)
5 – 7
6
 
Uranium
—

(2
)
 
Discounted cash flow
Average forward uranium pricing($/pound)(b)
35 – 40
36
(a)
The derivative asset and liability balances are presented net of counterparty credit considerations.
(b)
Generally, significant increases (decreases) in this input in isolation would result in a significantly higher (lower) fair value measurement.
(c)
Generally, significant increases (decreases) in this input in isolation would result in a significantly lower (higher) fair value measurement.
(d)
Counterparty credit risk is applied only to counterparties with derivative asset balances. Ameren Missouri and Ameren Illinois credit risk is applied only to counterparties with derivative liability balances.
(e)
Not applicable.
(f)
Power valuations use visible third-party pricing evaluated by month for peak and off-peak demand through 2019. Valuations beyond 2019 use fundamentally modeled pricing by month for peak and off-peak demand.
(g)
The balance at Ameren is comprised of Ameren Missouri and Ameren Illinois power contracts, which respond differently to unobservable input changes because of their opposing positions.
(h)
Escalation rate applies to power prices 2026 and beyond.
(i)
Escalation rate applies to fuel oil prices 2017 and beyond.

In accordance with applicable authoritative accounting guidance, we consider nonperformance risk in our valuation of derivative instruments by analyzing the credit standing of our counterparties and considering any counterparty credit enhancements (e.g., collateral). The guidance also requires that the fair value measurement of liabilities reflect the nonperformance risk of the reporting entity, as applicable. Therefore, we have factored the impact of our credit standing, as well as any potential credit enhancements, into the fair value measurement of both derivative assets and derivative liabilities. Included in our valuation, and based on current market conditions, is a valuation adjustment for counterparty default derived from market data such as the price of credit default swaps, bond yields, and credit ratings. No gains or losses related to valuation adjustments for counterparty default risk were recorded at Ameren, Ameren Missouri, or Ameren Illinois in 2015, 2014 or 2013. At December 31, 2015 and 2014, the counterparty default risk valuation adjustment related to derivative contracts was immaterial for Ameren, Ameren Missouri, and Ameren Illinois.
The following table sets forth, by level within the fair value hierarchy, our assets and liabilities measured at fair value on a recurring basis as of December 31, 2015:
 
 
 
Quoted Prices in
Active Markets for
Identical Assets
or Liabilities
(Level 1)
 
Significant Other
Observable
Inputs
(Level 2)
 
Significant Other
Unobservable
Inputs
(Level 3)
 
Total
 
Assets:
 
 
 
 
 
 
 
 
 
 
Ameren
Derivative assets – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Natural gas
 
$
—

 
$
1

 
$
1

 
$
2

 
 
Power
 
—

 
—

 
16

 
16

 
 
Total derivative assets – commodity contracts
 
$
—

 
$
1

 
$
17

 
$
18

 
 
Nuclear decommissioning trust fund:
 
 
 
 
 
 
 
 
 
 
Cash and cash equivalents
 
$
4

 
$
—

 
$
—

 
$
4

 
 
Equity securities:
 
 
 
 
 
 
 
 
 
 
U.S. large capitalization
 
364

 
—

 
—

 
364

 
 
Debt securities:
 
 
 
 
 
 
 
 
 
 
U.S. Treasury and agency securities
 
—

 
109

 
—

 
109

 
 
Corporate bonds
 
—

 
58

 
—

 
58

 
 
Other
 
—

 
22

 
—

 
22

 
 
Total nuclear decommissioning trust fund
 
$
368

 
$
189

 
$
—

 
$
557

(b) 
 
Total Ameren
 
$
368

 
$
190

 
$
17

 
$
575

 
Ameren Missouri
Derivative assets – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Natural gas
 
$
—

 
$
—

 
$
1

 
$
1

 
 
Power
 
—

 
—

 
16

 
16

 
 
Total derivative assets – commodity contracts
 
$
—

 
$
—

 
$
17

 
$
17

 
 
Nuclear decommissioning trust fund:
 
 
 
 
 
 
 
 
 
 
Cash and cash equivalents
 
$
4

 
$
—

 
$
—

 
$
4

 
 
Equity securities:
 
 
 
 
 
 
 
 
 
 
U.S. large capitalization
 
364

 
—

 
—

 
364

 
 
Debt securities:
 
 
 
 
 
 
 
 
 
 
U.S. Treasury and agency securities
 
—

 
109

 
—

 
109

 
 
Corporate bonds
 
—

 
58

 
—

 
58

 
 
Other
 
—

 
22

 
—

 
22

 
 
Total nuclear decommissioning trust fund
 
$
368

 
$
189

 
$
—

 
$
557

(b) 
 
Total Ameren Missouri
 
$
368

 
$
189

 
$
17

 
$
574

 
Ameren Illinois
Derivative assets – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Natural gas
 
$
—

 
$
1

 
$
—

 
$
1

 
Liabilities:
 
 
 
 
 
 
 
 
 
 
Ameren
Derivative liabilities – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
29

 
$
—

 
$
—

 
$
29

 
 
Natural gas
 
1

 
62

 
1

 
64

 
 
Power
 
—

 
—

 
170

 
170

 
 
Uranium
 
—

 
—

 
1

 
1

 
 
Total Ameren
 
$
30

 
$
62

 
$
172

 
$
264

 
 
 
 
Quoted Prices in
Active Markets for
Identical Assets
or Liabilities
(Level 1)
 
Significant Other
Observable
Inputs
(Level 2)
 
Significant Other
Unobservable
Inputs
(Level 3)
 
Total
 
Ameren Missouri
Derivative liabilities – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
29

 
$
—

 
$
—

 
$
29

 
 
Natural gas
 
—

 
13

 
1

 
14

 
 
Power
 
—

 
—

 
—

 
—

 
 
Uranium
 
—

 
—

 
1

 
1

 
 
Total Ameren Missouri
 
$
29

 
$
13

 
$
2

 
$
44

 
Ameren Illinois
Derivative liabilities – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Natural gas
 
$
1

 
$
49

 
$
—

 
$
50

 
 
Power
 
—

 
—

 
170

 
170

 
 
Total Ameren Illinois
 
$
1

 
$
49

 
$
170

 
$
220

 
(a)
The derivative asset and liability balances are presented net of counterparty credit considerations.
(b)
Balance excludes $(1) million of receivables, payables, and accrued income, net.
The following table sets forth, by level within the fair value hierarchy, our assets and liabilities measured at fair value on a recurring basis as of December 31, 2014:
 
 
 
Quoted Prices in
Active Markets for
Identical Assets
or Liabilities
(Level 1)
 
Significant Other
Observable Inputs
(Level 2)
 
Significant
Other
Unobservable
Inputs
(Level 3)
 
Total
 
Assets:
 
 
 
 
 
 
 
 
 
 
Ameren
Derivative assets – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
—

 
$
—

 
$
2

 
$
2

 
 
Natural gas
 
—

 
1

 
1

 
2

 
 
Power
 
—

 
4

 
11

 
15

 
 
Total derivative assets – commodity contracts
 
$
—

 
$
5

 
$
14

 
$
19

 
 
Nuclear decommissioning trust fund:
 
 
 
 
 
 
 
 
 
 
Cash and cash equivalents
 
$
1

 
$
—

 
$
—

 
$
1

 
 
Equity securities:
 
 
 
 
 
 
 
 
 
 
U.S. large capitalization
 
364

 
—

 
—

 
364

 
 
Debt securities:
 
 
 
 
 
 
 
 
 
 
U.S. Treasury and agency securities
 
—

 
102

 
—

 
102

 
 
Corporate bonds
 
—

 
63

 
—

 
63

 
 
Other
 
—

 
17

 
—

 
17

 
 
Total nuclear decommissioning trust fund
 
$
365

 
$
182

 
$
—

 
$
547

(b) 
 
Total Ameren
 
$
365

 
$
187

 
$
14

 
$
566

 
Ameren Missouri
Derivative assets – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
—

 
$
—

 
$
2

 
$
2

 
 
Natural gas
 
—

 
1

 
—

 
1

 
 
Power
 
—

 
4

 
11

 
15

 
 
Total derivative assets – commodity contracts
 
$
—

 
$
5

 
$
13

 
$
18

 
 
Nuclear decommissioning trust fund:
 
 
 
 
 
 
 
 
 
 
Cash and cash equivalents
 
$
1

 
$
—

 
$
—

 
$
1

 
 
Equity securities:
 
 
 
 
 
 
 
 
 
 
U.S. large capitalization
 
364

 
—

 
—

 
364

 
 
Debt securities:
 
 
 
 
 
 
 
 
 
 
U.S. Treasury and agency securities
 
—

 
102

 
—

 
102

 
 
Corporate bonds
 
—

 
63

 
—

 
63

 
 
Other
 
—

 
17

 
—

 
17

 
 
Total nuclear decommissioning trust fund
 
$
365

 
$
182

 
$
—

 
$
547

(b) 
 
Total Ameren Missouri
 
$
365

 
$
187

 
$
13

 
$
565

 
Ameren Illinois
Derivative assets – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Natural gas
 
$
—

 
$
—

 
$
1

 
$
1

 
 
 
 
Quoted Prices in
Active Markets for
Identical Assets
or Liabilities
(Level 1)
 
Significant Other
Observable Inputs
(Level 2)
 
Significant
Other
Unobservable
Inputs
(Level 3)
 
Total
 
Liabilities:
 
 
 
 
 
 
 
 
 
 
Ameren
Derivative liabilities – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
21

 
$
—

 
$
8

 
$
29

 
 
Natural gas
 
1

 
53

 
2

 
56

 
 
Power
 
—

 
1

 
144

 
145

 
 
Uranium
 
—

 
—

 
2

 
2

 
 
Total Ameren
 
$
22

 
$
54

 
$
156

 
$
232

 
Ameren Missouri
Derivative liabilities – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
21

 
$
—

 
$
8

 
$
29

 
 
Natural gas
 
1

 
10

 
1

 
12

 
 
Power
 
—

 
1

 
2

 
3

 
 
Uranium
 
—

 
—

 
2

 
2

 
 
Total Ameren Missouri
 
$
22

 
$
11

 
$
13

 
$
46

 
Ameren Illinois
Derivative liabilities – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Natural gas
 
$
—

 
$
43

 
$
1

 
$
44

 
 
Power
 
—

 
—

 
142

 
142

 
 
Total Ameren Illinois
 
$
—

 
$
43

 
$
143

 
$
186

 
(a)
The derivative asset and liability balances are presented net of counterparty credit considerations.
(b)
Balance excludes $2 million of receivables, payables, and accrued income, net.

The following table summarizes the changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the year ended December 31, 2015:
  
 
Net Derivative Commodity Contracts
  
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
Fuel oils:
 
 
 
 
 
 
Beginning balance at January 1, 2015
$
(6
)
$
(a)

$
(6
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities:
 
(1
)
 
(a)

 
(1
)
Settlements
 
5

 
(a)

 
5

Transfers out of Level 3
 
2

 
(a)

 
2

Ending balance at December 31, 2015
$
—

$
(a)

$
—

Change in unrealized gains (losses) related to assets/liabilities held at December 31, 2015
$
—

$
(a)

$
—

Natural gas:
 
 
 
 
 
 
Beginning balance at January 1, 2015
$
(1
)
$
—

$
(1
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities:

 
—

 
1

 
1

Settlements
 
1

 
(1
)
 
—

Ending balance at December 31, 2015
$
—

$
—

$
—

Change in unrealized gains (losses) related to assets/liabilities held at December 31, 2015
$
—

$
—

$
—

Power:
 
 
 
 
 
 
Beginning balance at January 1, 2015
$
9

$
(142
)
$
(133
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities:

 
2

 
(41
)
 
(39
)
Purchases
 
29

 
—

 
29

Settlements
 
(23
)
 
13

 
(10
)
Transfers out of Level 3
 
(1
)
 
—

 
(1
)
Ending balance at December 31, 2015
$
16

$
(170
)
$
(154
)
Change in unrealized gains (losses) related to assets/liabilities held at December 31, 2015
$
—

$
(39
)
$
(39
)
Uranium:
 
 
 
 
 
 
Beginning balance at January 1, 2015
$
(2
)
$
(a)

$
(2
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities:

 
(1
)
 
(a)

 
(1
)
Settlements
 
2

 
(a)

 
2

Ending balance at December 31, 2015
$
(1
)
$
(a)

$
(1
)
Change in unrealized gains (losses) related to assets/liabilities held at December 31, 2015
$
—

$
(a)

$
—

(a)
Not applicable.
The following table summarizes the changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the year ended December 31, 2014:
  
 
Net Derivative Commodity Contracts
  
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
Fuel oils:
 
 
 
 
 
 
Beginning balance at January 1, 2014
$
5

$
(a)

$
5

Realized and unrealized gains (losses) included in regulatory assets/liabilities:

 
(9
)
 
(a)

 
(9
)
Settlements
 
(2
)
 
(a)

 
(2
)
Ending balance at December 31, 2014
$
(6
)
$
(a)

$
(6
)
Change in unrealized gains (losses) related to assets/liabilities held at December 31, 2014
$
(6
)
$
(a)

$
(6
)
Natural gas:
 
 
 
 
 
 
Beginning balance at January 1, 2014
$
—

$
—

$
—

Realized and unrealized gains (losses) included in regulatory assets/liabilities:

 
—

 
1

 
1

Purchases
 
—

 
(2
)
 
(2
)
Sales
 
(1
)
 
—

 
(1
)
Settlements
 
—

 
1

 
1

Ending balance at December 31, 2014
$
(1
)
$
—

$
(1
)
Change in unrealized gains (losses) related to assets/liabilities held at December 31, 2014
$
—

$
2

$
2

Power:
 
 
 
 
 
 
Beginning balance at January 1, 2014
$
19

$
(108
)
$
(89
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities:

 
(14
)
 
(39
)
 
(53
)
Purchases
 
34

 
—

 
34

Sales
 
(1
)
 
—

 
(1
)
Settlements
 
(29
)
 
5

 
(24
)
Ending balance at December 31, 2014
$
9

$
(142
)
$
(133
)
Change in unrealized gains (losses) related to assets/liabilities held at December 31, 2014
$
—

$
(43
)
$
(43
)
Uranium:
 
 
 
 
 
 
Beginning balance at January 1, 2014
$
(6
)
$
(a)

$
(6
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities:

 
(1
)
 
(a)

 
(1
)
Settlements
 
5

 
(a)

 
5

Ending balance at December 31, 2014
$
(2
)
$
(a)

$
(2
)
Change in unrealized gains (losses) related to assets/liabilities held at December 31, 2014
$
(1
)
$
(a)

$
(1
)
(a)
Not applicable.
Transfers into or out of Level 3 represent either (1) existing assets and liabilities that were previously categorized as a higher level, but were recategorized to Level 3 because the inputs to the model became unobservable during the period, or (2) existing assets and liabilities that were previously classified as Level 3, but were recategorized to a higher level because the lowest significant input became observable during the period. Transfers between Level 1 and Level 3 for fuel oils and between Level 2 and Level 3 for power derivatives were primarily caused by changes in availability of similar financial trades observable on electronic exchanges between the periods. Any reclassifications are reported as transfers out of Level 3 at the fair value measurement reported at the beginning of the period in which the changes occur.
See Note 11 – Retirement Benefits for the fair value hierarchy tables detailing Ameren’s pension and postretirement plan assets as of December 31, 2015, as well as a table summarizing the changes in Level 3 plan assets during 2015.
The Ameren Companies’ carrying amounts of cash and cash equivalents approximate fair value because of the short-term nature of these instruments. They are considered to be Level 1 in the fair value hierarchy. The Ameren Companies' short-term borrowings also approximate fair value because of their short-term nature. Short-term borrowings are considered to be Level 2 in the fair value hierarchy as they are valued based on market rates for similar market transactions. The estimated fair value of long-term debt and preferred stock is based on the quoted market prices for same or similar issuances for companies with similar credit profiles or on the current rates offered to the Ameren Companies for similar financial instruments, which fair value measurement is considered Level 2 in the fair value hierarchy.
The following table presents the carrying amounts and estimated fair values of our long-term debt, capital lease obligations and preferred stock at December 31, 2015 and 2014:
  
2015
 
2014
  
Carrying Amount
 
Fair Value
 
Carrying Amount
 
Fair Value
Ameren:(a)
 
 
 
 
 
 
 
Long-term debt and capital lease obligations (including current portion)(b)
$
7,275

 
$
7,814

 
$
6,205

 
$
7,135

Preferred stock
142

 
125

 
142

 
122

Ameren Missouri:
 
 
 
 
 
 
 
Long-term debt and capital lease obligations (including current portion)(b)
$
4,110

 
$
4,449

 
$
3,981

 
$
4,518

Preferred stock
80

 
75

 
80

 
73

Ameren Illinois:
 
 
 
 
 
 
 
Long-term debt (including current portion)(b)
$
2,471

 
$
2,665

 
$
2,224

 
$
2,517

Preferred stock
62

 
50

 
62

 
49

(a)
Preferred stock is recorded in "Noncontrolling Interests" on the consolidated balance sheet.
(b)
Carrying amounts reflect the adoption of the new authoritative accounting guidance for the presentation of debt issuance costs. See Note 1 – Summary of Significant Accounting Policies
Nuclear Decommissioning Trust Fund Investments
NUCLEAR DECOMMISSIONING TRUST FUND INVESTMENTS
NUCLEAR DECOMMISSIONING TRUST FUND INVESTMENTS
Ameren Missouri has investments in debt and equity securities that are held in a trust fund for the purpose of funding the decommissioning of its Callaway energy center. We have classified these investments as available for sale, and we have recorded all such investments at their fair market value at December 31, 2015, and 2014. See Note 10 – Callaway Energy Center for additional information.
Investments in the nuclear decommissioning trust fund have a target allocation of 60% to 70% in equity securities, with the balance invested in debt securities.
The following table presents proceeds from the sale and maturities of investments in Ameren Missouri’s nuclear decommissioning trust fund and the gross realized gains and losses resulting from those sales for the years ended December 31, 2015, 2014, and 2013:
 
2015
 
2014
 
2013
Proceeds from sales and maturities
$
349

 
$
391

 
$
196

Gross realized gains
8

 
7

 
7

Gross realized losses
2

 
2

 
5


Net realized and unrealized gains and losses are deferred and recorded as a regulatory asset or a regulatory liability on Ameren’s and Ameren Missouri’s balance sheets. This reporting is consistent with the method used to account for the decommissioning costs recovered in rates. Gains or losses associated with assets in the trust fund could result in lower or higher funding requirements for decommissioning costs, which are expected to be reflected in electric rates paid by Ameren Missouri’s customers. See Note 2 – Rate and Regulatory Matters.
The following table presents the costs and fair values of investments in debt and equity securities in Ameren's and Ameren Missouri’s nuclear decommissioning trust fund at December 31, 2015 and 2014:
Security Type
Cost
 
Gross Unrealized Gain
 
Gross Unrealized Loss
 
Fair Value
2015
 
 
 
 
 
 
 
Debt securities
$
191

 
$
2

$
4

 
$
189

Equity securities
147

 
224

 
7

 
364

Cash
4

 
—

 
—

 
4

Other(a)
(1
)
 
—

 
—

 
(1
)
Total
$
341

 
$
226

$
11

 
$
556

2014
 
 
 
 
 
 
 
Debt securities
$
175

 
$
7

$
—

 
$
182

Equity securities
138

 
230

 
4

 
364

Cash
1

 
—

 
—

 
1

Other(a)
2

 
—

 
—

 
2

Total
$
316

 
$
237

$
4

 
$
549


(a)
Represents payables relating to pending security purchases, net of receivables related to pending security sales and interest.
The following table presents the costs and fair values of investments in debt securities in Ameren's and Ameren Missouri’s nuclear decommissioning trust fund according to their contractual maturities at December 31, 2015:
 
Cost
 
Fair Value
Less than 5 years
$
106

 
$
105

5 years to 10 years
42

 
41

Due after 10 years
43

 
43

Total
$
191

 
$
189


We have unrealized losses relating to certain available-for-sale investments included in our nuclear decommissioning trust fund, recorded as a regulatory asset as discussed above. Decommissioning will not occur until our nuclear energy center is retired. Ameren Missouri received a license extension from the NRC in March 2015 to extend the Callaway energy center’s operating license to 2044. The following table presents the fair value and the gross unrealized losses of the available-for-sale securities held in Ameren's and Ameren Missouri's nuclear decommissioning trust fund. They are aggregated by investment category and the length of time that individual securities have been in a continuous unrealized loss position at December 31, 2015:
  
Less than 12 Months
 
 
12 Months or Greater
 
Total
  
Fair Value
 
Gross
Unrealized
Losses
 
 
Fair Value
 
Gross
Unrealized
Losses
 
Fair Value
 
Gross
Unrealized
Losses
Debt securities
$
136

$
3

 
 
$
4

$
1

 
$
140

$
4

Equity securities
16

 
3

 
 
4

 
4

 
20

 
7

Total
$
152

$
6

 
 
$
8

$
5

 
$
160

$
11

Callaway Energy Center
CALLAWAY ENERGY CENTER
CALLAWAY ENERGY CENTER
Under the NWPA, the DOE is responsible for disposing of spent nuclear fuel from the Callaway energy center and other commercial nuclear energy centers. Under the NWPA, Ameren Missouri and other owners of nuclear energy centers are responsible for paying the disposal costs. The NWPA established the fee that these utilities pay the federal government for disposing of the spent nuclear fuel at one mill, or one-tenth of one cent, for each kilowatthour generated and sold by those plants. The NWPA also requires the DOE to review the nuclear waste fee annually against the cost of the nuclear waste disposal program and to propose to the United States Congress any fee adjustment necessary to offset the costs of the program. As required by the NWPA, Ameren Missouri and other utilities have entered into standard contracts with the DOE. Consistent with the NWPA and its standard contract, Ameren Missouri had historically collected one mill from its electric customers for each kilowatthour of electricity that it generated and sold from its Callaway energy center. Because the federal government is not meeting its disposal obligation, the collection of this fee is currently suspended.
Although both the NWPA and the standard contract stated that the DOE would begin to dispose of spent nuclear fuel by 1998, the DOE is not meeting its disposal obligation. The DOE's delay in carrying out its obligation to dispose of spent nuclear fuel from the Callaway energy center is not expected to adversely affect the continued operations of the energy center. Ameren Missouri has sufficient capacity in the spent fuel pool and dry spent storage facility at the Callaway energy center to store its spent nuclear fuel generated through the end of the energy center’s operating license in 2044.
As a result of the DOE's failure to begin to dispose of spent nuclear fuel from commercial nuclear energy centers and fulfill its contractual obligations, Ameren Missouri and other nuclear energy center owners sued the DOE to recover costs, such as certain NRC fees and Missouri ad valorem taxes, incurred for ongoing storage of their spent fuel. The lawsuit resulted in a settlement agreement that provides for annual recovery of additional spent fuel storage and related costs incurred from 2010 through 2016, with the ability to extend the recovery period as mutually agreed upon by the parties. Included in these reimbursements are costs related to the dry spent fuel storage facility at the Callaway energy center, to which Ameren Missouri began transferring spent fuel assemblies in 2015. Ameren Missouri will continue to apply for reimbursement from the DOE for allowable costs associated with the ongoing storage of spent fuel.
Electric utility rates charged to customers provide for the recovery of the Callaway energy center's decommissioning costs, which include decontamination, dismantling, and site restoration costs, over the expected life of the nuclear energy center. Amounts collected from customers are deposited into the external nuclear decommissioning trust fund to provide for the Callaway energy center’s decommissioning. It is assumed that the Callaway energy center site will be decommissioned through the immediate dismantlement method and removed from service. Ameren and Ameren Missouri have recorded an ARO for the Callaway energy center decommissioning costs at fair value, which represents the present value of estimated future cash outflows. Annual decommissioning costs of $7 million are included in the costs used to establish electric rates for Ameren Missouri's customers. Every three years, the MoPSC requires Ameren Missouri to file an updated cost study and funding analysis for decommissioning its Callaway energy center. Following the NRC’s decision in March 2015 to extend the Callaway energy center’s operating license from 2024 to 2044, an updated cost study and a revised funding analysis were filed with the MoPSC in April 2015. Ameren Missouri’s April 2015 filing supported no change in electric service rates for decommissioning costs. There is no time requirement by which the MoPSC must issue an order regarding the decommissioning cost included in Ameren Missouri’s electric service rates. If the assumed return on trust assets is not earned, we believe that it is probable that any such earnings deficiency will be recovered in rates. The fair value of the trust fund for Ameren Missouri's Callaway energy center is reported as "Nuclear decommissioning trust fund" in Ameren's and Ameren Missouri's balance sheets. This amount is legally restricted and may be used only to fund the costs of nuclear decommissioning. Changes in the fair value of the trust fund are recorded as an increase or decrease to the nuclear decommissioning trust fund, with an offsetting adjustment to the related regulatory liability.
See Note 2 – Rate and Regulatory Matters and Note 9 – Nuclear Decommissioning Trust Fund Investments for additional information related to the Callaway energy center.
Retirement Benefits
RETIREMENT BENEFITS
RETIREMENT BENEFITS
The primary objective of the Ameren pension and postretirement benefit plans is to provide eligible employees with pension and postretirement health care and life insurance benefits. Ameren offers defined benefit pension and postretirement benefit plans covering substantially all of its union employees. Ameren offers defined benefit pension plans covering substantially all of its non-union employees and postretirement benefit plans covering non-union employees hired before October 2015. Ameren uses a measurement date of December 31 for its pension and postretirement benefit plans. Ameren Missouri and Ameren Illinois each participate in Ameren’s single-employer pension and other postretirement plans. Ameren’s qualified pension plan is the Ameren Retirement Plan. Ameren also has an unfunded nonqualified pension plan, the Ameren Supplemental Retirement Plan, which is available to provide certain management employees and retirees with a supplemental benefit when their qualified pension plan benefits are capped in compliance with Internal Revenue Code limitations. Ameren’s other postretirement plans are the Ameren Retiree Medical Plan and the Ameren Group Life Insurance Plan. Only Ameren subsidiaries participate in the plans listed above.
In December 2013, Ameren completed the divestiture of New AER to IPH. In accordance with the transaction agreement, Ameren retained the pension obligations as of December 2, 2013, associated with the current and former employees of New AER and its subsidiaries who were included in the Ameren Retirement Plan and the Ameren Supplemental Retirement Plan. Ameren also retained the postretirement benefit obligations associated with the employees of New AER and its subsidiaries who were eligible to retire at December 2, 2013, and who were included in the Ameren Retiree Medical Plan and the Ameren Group Life Insurance Plan.
Ameren’s unfunded obligation under its pension and other postretirement benefit plans was $567 million and $710 million as of December 31, 2015, and December 31, 2014, respectively. These net liabilities are recorded in "Other current liabilities," "Pension and other postretirement benefits," and "Other assets" on Ameren's consolidated balance sheet. The primary factor contributing to the decrease in the unfunded obligation during 2015 was a 50 basis point increase in the pension and other postretirement benefit plan discount rates used to determine the present value of the obligation. The decrease in the unfunded obligation also resulted in a decrease to "Regulatory assets" on Ameren's, Ameren Missouri's, and Ameren Illinois' consolidated balance sheet.
The following table presents the net benefit liability recorded on the balance sheets of each of the Ameren Companies as of December 31, 2015 and 2014:
 
2015

2014

Ameren(a)
$
567

$
710

Ameren Missouri
236

277

Ameren Illinois
219

278

(a)
Includes amounts for Ameren registrant and nonregistrant subsidiaries.
Ameren recognizes the underfunded status of its pension and postretirement plans as a liability on its consolidated balance sheet, with offsetting entries to accumulated OCI and regulatory assets, in accordance with authoritative accounting guidance. The following table presents the funded status of Ameren's pension and postretirement benefit plans as of December 31, 2015 and 2014. It also provides the amounts included in regulatory assets and accumulated OCI at December 31, 2015 and 2014, that have not been recognized in net periodic benefit costs.
  
2015
 
2014
  
Pension Benefits(a)
 
Postretirement
Benefits(a)
 
Pension Benefits(a)
 
Postretirement
Benefits(a)
Accumulated benefit obligation at end of year
$
3,995

$
(b)

 
$
4,176

$
(b)

Change in benefit obligation:
 
 
 
 
 
 
 
Net benefit obligation at beginning of year
$
4,410

$
1,203

 
$
3,900

$
1,096

Service cost
92

 
24

 
79

 
19

Interest cost
174

 
48

 
183

 
50

Participant contributions
—

 
8

 
—

 
16

Actuarial (gain) loss
(256
)
 
(133
)
 
462

 
84

Settlement
(2
)
 
—

 
—

 
—

Benefits paid
(221
)
 
(56
)
 
(214
)
 
(65
)
Federal subsidy on benefits paid
(b)

 
—

 
(b)

 
3

Net benefit obligation at end of year
4,197

 
1,094

 
4,410

 
1,203

Change in plan assets:
 
 
 
 
 
 
 
Fair value of plan assets at beginning of year
3,794

 
1,109

 
3,461

 
1,074

Actual return on plan assets
(29
)
 
(8
)
 
448

 
75

Employer contributions
111

 
18

 
99

 
6

Federal subsidy on benefits paid
(b)

 
—

 
(b)

 
3

Participant contributions
—

 
8

 
—

 
16

Settlements
(2
)
 
—

 
—

 
—

Benefits paid
(221
)
 
(56
)
 
(214
)
 
(65
)
Fair value of plan assets at end of year
3,653

 
1,071

 
3,794

 
1,109

Funded status – deficiency
544

 
23

 
616

 
94

Accrued benefit cost at December 31
$
544

$
23

 
$
616

$
94

Amounts recognized in the balance sheet consist of:
 
 
 
 
 
 
 
Noncurrent asset(c)
$
—

$
(18
)
 
$
—

$
—

Current liability(d)
3

 
2

 
3

 
2

Noncurrent liability
541

 
39

 
613

 
92

Net liability recognized
$
544

$
23

 
$
616

$
94

Amounts recognized in regulatory assets consist of:
 
 
 
 
 
 
 
Net actuarial (gain) loss
$
395

$
(82
)
 
$
452

$
(7
)
Prior service cost (credit)
(5
)
 
(11
)
 
(6
)
 
(16
)
Amounts (pretax) recognized in accumulated OCI consist of:
 
 
 
 
 
 
 
Net actuarial (gain) loss
17

 
(3
)
 
29

 
(5
)
Prior service cost (credit)
—

 
—

 
—

 
(1
)
Total
$
407

$
(96
)
 
$
475

$
(29
)
(a)
Includes amounts for Ameren registrant and nonregistrant subsidiaries.
(b)
Not applicable.
(c)
Included in "Other assets" on Ameren's consolidated balance sheet.
(d)
Included in "Other current liabilities" on Ameren's consolidated balance sheet.
The following table presents the assumptions used to determine our benefit obligations at December 31, 2015 and 2014:
  
Pension Benefits
 
Postretirement Benefits
  
2015
 
2014
 
2015
 
2014
Discount rate at measurement date
4.50
%
 
4.00
%
 
4.50
%
 
4.00
%
Increase in future compensation
3.50

 
3.50

 
3.50

 
3.50

Medical cost trend rate (initial)
(a)

 
(a)

 
5.00

 
5.00

Medical cost trend rate (ultimate)
(a)

 
(a)

 
5.00

 
5.00

Years to ultimate rate
(a)

 
(a)

 
—

 
—


(a)
Not applicable
Ameren determines discount rate assumptions by identifying a theoretical settlement portfolio of high-quality corporate bonds sufficient to provide for a plan's projected benefit payments. The settlement portfolio of bonds is selected from a pool of more than 700 high-quality corporate bonds. A single discount rate is then determined; that rate results in a discounted value of the plan's benefit payments that equates to the market value of the selected bonds. In addition, during 2015, Ameren adopted the Society of Actuaries 2015 Mortality Tables Report and Mortality Improvement Scale. The updated mortality tables assume a lower rate of mortality improvement as compared to the 2014 Mortality Tables Report and Mortality Improvement Scale that Ameren adopted in 2014. The 2015 tables lowered projected improvements in life expectancies for our employees and retirees, resulting in a decrease to our pension and other postretirement benefit obligations.
Funding
Pension benefits are based on the employees’ years of service, age, and compensation. Ameren’s pension plans are funded in compliance with income tax regulations, federal funding, and other regulatory requirements. As a result, Ameren expects to fund its pension plan at a level equal to the greater of the pension expense or the legally required minimum contribution. Considering its assumptions at December 31, 2015, its investment performance in 2015, and its pension funding policy, Ameren expects to make annual contributions of $40 million to $70 million in each of the next five years, with aggregate estimated contributions of $280 million. We expect Ameren Missouri’s and Ameren Illinois’ portion of the future funding requirements to be 40% and 50%, respectively. These amounts are estimates. They may change based on actual investment performance, changes in interest rates, changes in our assumptions, changes in government regulations, and any voluntary contributions. Our funding policy for postretirement benefits is primarily to fund the Voluntary Employee Beneficiary Association (VEBA) trusts to match the annual postretirement expense.
The following table presents the cash contributions made to our defined benefit retirement plan and to our postretirement plans during 2015, 2014, and 2013:
  
Pension Benefits
 
Postretirement Benefits
  
2015
 
2014
 
2013
 
2015
 
2014
 
2013
Ameren Missouri
$
47

 
$
41

 
$
60

 
$
8

 
$
3

 
$
10

Ameren Illinois
45

 
39

 
50

 
8

 
2

 
11

Other
19

 
19

 
46

 
2

 
1

 
4

Ameren(a)
111

 
99

 
156

 
18

 
6

 
25

(a)
Includes amounts for Ameren registrant and nonregistrant subsidiaries.
Investment Strategy and Policies
Ameren manages plan assets in accordance with the “prudent investor” guidelines contained in ERISA. The investment committee, which includes members of senior management, approves and implements investment strategy and asset allocation guidelines for the plan assets. The investment committee’s goals are twofold: first, to ensure that sufficient funds are available to provide the benefits at the time they are payable; and second, to maximize total return on plan assets and to minimize expense volatility consistent with its tolerance for risk. Ameren delegates the task of investment management to specialists in each asset class. As appropriate, Ameren provides each investment manager with guidelines that specify allowable and prohibited investment types. The investment committee regularly monitors manager performance and compliance with investment guidelines.
The expected return on plan assets assumption is based on historical and projected rates of return for current and planned asset classes in the investment portfolio. Projected rates of return for each asset class were estimated after an analysis of historical experience, future expectations, and the volatility of the various asset classes. After considering the target asset allocation for each asset class, we adjusted the overall expected rate of return for the portfolio for historical and expected experience of active portfolio management results compared with benchmark returns and for the effect of expenses paid from plan assets. Ameren will use an expected return on plan assets for its pension and postretirement plan assets of 7.00%, in 2016. No plan assets are expected to be returned to Ameren during 2016.
Ameren’s investment committee strives to assemble a portfolio of diversified assets that does not create a significant concentration of risks. The investment committee develops asset allocation guidelines between asset classes, and it creates diversification through investments in assets that differ by type (equity, debt, real estate, private equity), duration, market capitalization, country, style (growth or value) and industry, among other factors. The diversification of assets is displayed in the target allocation table below. The investment committee also routinely rebalances the plan assets to adhere to the diversification goals. The investment committee’s strategy reduces the concentration of investment risk; however, Ameren is still subject to overall market risk. The following table presents our target allocations for 2016 and our pension and postretirement plans’ asset categories as of December 31, 2015 and 2014:
Asset
Category
Target Allocation
2016
 
Percentage of Plan Assets at December  31,
2015
 
2014
Pension Plan:
 
 
 
 
 
Cash and cash equivalents
0% – 5%
 
1
%
 
2
%
Equity securities:
 
 
 
 
 
U.S. large-capitalization
29% – 39%
 
34
%
 
34
%
U.S. small- and mid-capitalization
3% – 13%
 
7
%
 
7
%
International and emerging markets
9% – 19%
 
13
%
 
12
%
Total equity
51% – 61%
 
54
%
 
53
%
Debt securities
35% – 45%
 
40
%
 
41
%
Real estate
0% –  9%  
 
5
%
 
4
%
Private equity
0% –  5%  
 
(a)

 
(a)

Total
 
 
100
%
 
100
%
Postretirement Plans:
 
 
 
 
 
Cash and cash equivalents
0% – 7%
 
4
%
 
4
%
Equity securities:
 
 
 
 
 
U.S. large-capitalization
34% – 44%
 
39
%
 
40
%
U.S. small- and mid-capitalization
2% – 12%
 
7
%
 
7
%
International
9% – 19%
 
13
%
 
13
%
Total equity
55% – 65%
 
59
%
 
60
%
Debt securities
33% – 43%
 
37
%
 
36
%
Total
 
 
100
%
 
100
%

(a)
Less than 1% of plan assets.
In general, the United States large-capitalization equity investments are passively managed or indexed, whereas the international, emerging markets, United States small-capitalization, and United States mid-capitalization equity investments are actively managed by investment managers. Debt securities include a broad range of fixed-income vehicles. Debt security investments in high-yield securities, emerging market securities, and non-United-States-dollar-denominated securities are owned by the plans, but in limited quantities to reduce risk. Most of the debt security investments are under active management by investment managers. Real estate investments include private real estate vehicles; however, Ameren does not, by policy, hold direct investments in real estate property. Ameren’s investment in private equity funds is spread among eight different limited partnerships, with invested capital ranging from less than $1 million to $4 million in each, which invest primarily in a diversified number of small United States-based companies. Ameren is seeking to eliminate its private equity investments over time. Additionally, Ameren’s investment committee allows investment managers to use derivatives, such as index futures, exchange traded funds, foreign exchange futures, and options, in certain situations, to increase or to reduce market exposure in an efficient and timely manner.
Fair Value Measurements of Plan Assets
Investments in the pension and postretirement benefit plans were stated at fair value as of December 31, 2015. The fair value of an asset is the amount that would be received upon its sale in an orderly transaction between market participants at the measurement date. Cash and cash equivalents have initial maturities of three months or less and are recorded at cost plus accrued interest. The carrying amounts of cash and cash equivalents approximate fair value because of the short-term nature of these instruments. Investments traded in active markets on national or international securities exchanges are valued at closing prices on the last business day on or before the measurement date. Securities traded in over-the-counter markets are valued based on quoted market prices, broker or dealer quotations, or alternative pricing sources with reasonable levels of price transparency. Investments measured under net asset valuation are based on the fair values of the underlying assets provided by the funds and their administrators. Derivative contracts are valued at fair value, as determined by the investment managers (or independent third parties on behalf of the investment managers), who use proprietary models and take into consideration exchange quotations on underlying instruments, dealer quotations, and other market information. The fair value of real estate is based on annual appraisal reports prepared by an independent real estate appraiser.
The following table sets forth, by level within the fair value hierarchy discussed in Note 8 – Fair Value Measurements, the pension plan assets measured at fair value as of December 31, 2015:
 
Quoted Prices in
Active Markets for
Identified Assets
(Level 1)
 
Significant Other
Observable Inputs
(Level 2)
 
Significant Other
Unobservable
Inputs
(Level 3)
 
Total
Cash and cash equivalents
$
—

 
$
20

 
$
—

 
$
20

Equity securities:
 
 
 
 
 
 
 
U.S. large-capitalization
—

 
1,296

 
—

 
1,296

U.S. small- and mid-capitalization
268

 
—

 
—

 
268

International and emerging markets
122

 
369

 
—

 
491

Debt securities:
 
 
 
 
 
 
 
Corporate bonds
—

 
631

 
—

 
631

Municipal bonds
—

 
104

 
—

 
104

U.S. Treasury and agency securities
6

 
751

 
—

 
757

Other
—

 
5

 
—

 
5

Real estate
—

 
—

 
168

 
168

Private equity
—

 
—

 
8

 
8

Total
$
396

 
$
3,176

 
$
176

 
$
3,748

Less: Medical benefit assets at December 31(a)
 
 
 
 
 
 
(123
)
Plus: Net receivables at December 31(b)
 
 
 
 
 
 
28

Fair value of pension plans assets at year end
 
 
 
 
 
 
$
3,653

(a)
Medical benefit (health and welfare) component for accounts maintained in accordance with Section 401(h) of the Internal Revenue Code to fund a portion of the postretirement obligation.
(b)
Receivables related to pending security sales, offset by payables related to pending security purchases.
The following table sets forth, by level within the fair value hierarchy discussed in Note 8 – Fair Value Measurements, the pension plan assets measured at fair value as of December 31, 2014:
 
Quoted Prices in
Active Markets for
Identified Assets or Liabilities
(Level 1)
 
Significant Other
Observable Inputs
(Level 2)
 
Significant Other
Unobservable
Inputs
(Level 3)
 
Total
Cash and cash equivalents
$
—

 
$
38

 
$
—

 
$
38

Equity securities:
 
 
 
 
 
 
 
U.S. large-capitalization
—

 
1,331

 
—

 
1,331

U.S. small- and mid-capitalization
270

 
—

 
—

 
270

International and emerging markets
134

 
360

 
—

 
494

Debt securities:
 
 
 
 
 
 
 
Corporate bonds
—

 
1,026

 
—

 
1,026

Municipal bonds
—

 
175

 
—

 
175

U.S. Treasury and agency securities
6

 
366

 
—

 
372

Other
—

 
31

 
—

 
31

Real estate
—

 
—

 
147

 
147

Private equity
—

 
—

 
13

 
13

Derivative assets
1

 
—

 
—

 
1

Total
$
411

 
$
3,327

 
$
160

 
$
3,898

Less: Medical benefit assets at December 31(a)
 
 
 
 
 
 
(125
)
Plus: Net receivables at December 31(b)
 
 
 
 
 
 
21

Fair value of pension plans assets at year end
 
 
 
 
 
 
$
3,794

(a)
Medical benefit (health and welfare) component for accounts maintained in accordance with Section 401(h) of the Internal Revenue Code to fund a portion of the postretirement obligation.
(b)
Receivables related to pending security sales, offset by payables related to pending security purchases.
The following table summarizes the changes in the fair value of the pension plan assets classified as Level 3 in the fair value hierarchy for each of the years ended December 31, 2015 and 2014:
 
Beginning
Balance at
January 1,
 
Actual Return on
Plan Assets Related
to Assets Still Held
at the Reporting Date
 
Actual Return on
Plan Assets Related
to Assets Sold
During the Period
 
Purchases,
Sales, and
Settlements, Net
 
Net
Transfers
into (out of)
of Level 3
 
Ending Balance at
December 31,
2015:
 
 
 
 
 
 
 
 
 
 
 
Real estate
$
147

 
$
14

 
$
—

 
$
7

 
$
—

 
$
168

Private equity
13

 
(9
)
 
9

 
(5
)
 
—

 
8

2014:
 
 
 
 
 
 
 
 
 
 
 
Real estate
$
131

 
$
11

 
$
—

 
$
5

 
$
—

 
$
147

Private equity
15

 
(9
)
 
10

 
(3
)
 
—

 
13


The following table sets forth, by level within the fair value hierarchy discussed in Note 8 – Fair Value Measurements, the postretirement benefit plans assets measured at fair value as of December 31, 2015:
 
Quoted Prices in
Active Markets for
Identified Assets
(Level 1)
 
Significant Other
Observable Inputs
(Level 2)
 
Significant Other
Unobservable
Inputs
(Level 3)
 
Total
Cash and cash equivalents
$
61

 
$
—

 
$
—

 
$
61

Equity securities:
 
 
 
 
 
 
 
U.S. large-capitalization
272

 
98

 
—

 
370

U.S. small- and mid-capitalization
65

 
—

 
—

 
65

International
33

 
93

 
—

 
126

Other
—

 
7

 
—

 
7

Debt securities:
 
 
 
 
 
 
 
Corporate bonds
—

 
138

 
—

 
138

Municipal bonds
—

 
114

 
—

 
114

U.S. Treasury and agency securities
—

 
55

 
—

 
55

Other
—

 
40

 
—

 
40

Total
$
431

 
$
545

 
$
—

 
$
976

Plus: Medical benefit assets at December 31(a)
 
 
 
 
 
 
123

Less: Net payables at December 31(b)
 
 
 
 
 
 
(28
)
Fair value of postretirement benefit plans assets at year end
 
 
 
 
 
 
$
1,071

(a)
Medical benefit (health and welfare) component for 401(h) accounts to fund a portion of the postretirement obligation. These 401(h) assets are included in the pension plan assets shown above.
(b)
Payables related to pending security purchases, offset by interest receivables and receivables related to pending security sales.
The following table sets forth, by level within the fair value hierarchy discussed in Note 8 – Fair Value Measurements, the postretirement benefit plans assets measured at fair value as of December 31, 2014:
 
Quoted Prices in
Active Markets for
Identified Assets
(Level 1)
 
Significant Other
Observable Inputs
(Level 2)
 
Significant Other
Unobservable
Inputs
(Level 3)
 
Total
Cash and cash equivalents
$
89

 
$
—

 
$
—

 
$
89

Equity securities:
 
 
 
 
 
 
 
U.S. large-capitalization
291

 
101

 
—

 
392

U.S. small- and mid-capitalization
70

 
—

 
—

 
70

International
37

 
94

 
—

 
131

Other
—

 
7

 
—

 
7

Debt securities:
 
 
 
 
 
 
 
Corporate bonds
—

 
105

 
—

 
105

Municipal bonds
—

 
111

 
—

 
111

U.S. Treasury and agency securities
—

 
89

 
—

 
89

Other
—

 
44

 
—

 
44

Total
$
487

 
$
551

 
$
—

 
$
1,038

Plus: Medical benefit assets at December 31(a)
 
 
 
 
 
 
125

Less: Net payables at December 31(b)
 
 
 
 
 
 
(54
)
Fair value of postretirement benefit plans assets at year end
 
 
 
 
 
 
$
1,109

(a)
Medical benefit (health and welfare) component for 401(h) accounts to fund a portion of the postretirement obligation. These 401(h) assets are included in the pension plan assets shown above.
(b)
Payables related to pending security purchases, offset by Medicare, interest receivables, and receivables related to pending security sales.
Net Periodic Benefit Cost
The following table presents the components of the net periodic benefit cost of Ameren's pension and postretirement benefit plans during 2015, 2014, and 2013:
 
Pension Benefits(a)
 
Postretirement Benefits(a)
2015
 
 
 
Service cost
$
92

 
$
24

Interest cost
174

 
48

Expected return on plan assets
(248
)
 
(68
)
Amortization of:
 
 
 
Prior service credit
(1
)
 
(5
)
Actuarial loss
74

 
5

Settlement Loss
1

 
—

Net periodic benefit cost
$
92

 
$
4

2014
 
 
 
Service cost
$
79

 
$
19

Interest cost
183

 
50

Expected return on plan assets
(229
)
 
(65
)
Amortization of:
 
 
 
Prior service credit
(1
)
 
(5
)
Actuarial (gain) loss
49

 
(7
)
Net periodic benefit cost (benefit)
$
81

 
$
(8
)
2013
 
 
 
Service cost
$
91

 
$
22

Interest cost
163

 
46

Expected return on plan assets
(218
)
 
(62
)
Amortization of:
 
 
 
Prior service credit
(2
)
 
(6
)
Actuarial loss
87

 
8

Curtailment gain
(12
)
 
(7
)
Net periodic benefit cost(b)
$
109

 
$
1

(a)
Includes amounts for Ameren registrant and nonregistrant subsidiaries.
(b)
The net periodic benefit cost includes a $6 million and a $7 million net gain for pension benefits and postretirement benefits, respectively, which was included in "Income (loss) from discontinued operations, net of taxes" on Ameren's consolidated statement of income (loss). This net gain includes the curtailment gain recognized in 2013 as a result of a significant reduction in employees as of the December 2, 2013 closing date of the New AER divestiture. See Note 16 – Divestiture Transactions and Discontinued Operations for additional information on the divestiture.
The estimated amounts that will be amortized from regulatory assets and accumulated OCI into Ameren's net periodic benefit cost in 2016 are as follows:
  
Pension Benefits(a)
 
Postretirement Benefits(a)
Regulatory assets:
 
 
 
Prior service credit
$
(1
)
 
$
(4
)
Net actuarial loss
46

 
(3
)
Accumulated OCI:
 
 
 
Net actuarial (gain) loss
(3
)
 
(2
)
Total
$
42

 
$
(9
)
(a)
Includes amounts for Ameren registrant and nonregistrant subsidiaries.
Prior service cost is amortized on a straight-line basis over the average future service of active participants benefiting under the plan amendment. The net actuarial (gain) loss subject to amortization is amortized on a straight-line basis over 10 years.
The Ameren Companies are responsible for their share of the pension and postretirement benefit costs. The following table presents the pension costs and the postretirement benefit costs incurred and included in continuing operations for the years ended December 31, 2015, 2014, and 2013:
  
Pension Costs
 
Postretirement Costs
  
2015
 
2014
 
2013
 
2015
 
2014
 
2013
Ameren Missouri(a)
$
54

 
$
50

 
$
69

 
$
8

 
$
3

 
$
8

Ameren Illinois
38

 
30

 
41

 
(3
)
 
(9
)
 
—

Other
—

 
1

 
5

 
(1
)
 
(2
)
 
—

Ameren(b)
92

 
81

 
115

 
4

 
(8
)
 
8

(a)
Does not include the impact of the regulatory tracking mechanism for the difference between the level of pension and postretirement benefit costs incurred by Ameren Missouri under GAAP and the level of such costs included in rates.
(b)
Includes amounts for Ameren registrant and nonregistrant subsidiaries.
The expected pension and postretirement benefit payments from qualified trust and company funds, which reflect expected future service, as of December 31, 2015, are as follows:
  
Pension Benefits
 
Postretirement Benefits
  
Paid from
Qualified
Trust Funds
 
        Paid from
         Company
      Funds
 
        Paid from
         Qualified
      Trust Funds
 
        Paid from
         Company
      Funds
2016
$
233

 
$
3

 
$
55

 
$
2

2017
244

 
3

 
58

 
2

2018
250

 
3

 
60

 
2

2019
257

 
3

 
62

 
2

2020
261

 
3

 
65

 
2

2021 – 2025
1,377

 
13

 
341

 
12


The following table presents the assumptions used to determine net periodic benefit cost for our pension and postretirement benefit plans for the years ended December 31, 2015, 2014, and 2013:
  
Pension Benefits
 
Postretirement Benefits
  
2015
 
2014
 
2013
 
2015
 
2014
 
2013
Discount rate at measurement date
4.00
%
 
4.75
%
 
4.00
%
 
4.00
%
 
4.75
%
 
4.00
%
Expected return on plan assets
7.25

 
7.25

 
7.50

 
7.00

 
7.00

 
7.25

Increase in future compensation
3.50

 
3.50

 
3.50

 
3.50

 
3.50

 
3.50

Medical cost trend rate (initial)
(a)

 
(a)

 
(a)

 
5.00

 
5.00

 
5.00

Medical cost trend rate (ultimate)
(a)

 
(a)

 
(a)

 
5.00

 
5.00

 
5.00

Years to ultimate rate
(a)

 
(a)

 
(a)

 
—

 
—

 
—


(a)
Not applicable
The table below reflects the sensitivity of Ameren’s plans to potential changes in key assumptions:
  
Pension Benefits
 
Postretirement Benefits
  
Service Cost
and Interest
Cost
 
    Projected
    Benefit
     Obligation
 
    Service Cost
    and Interest
    Cost
 
    Postretirement
      Benefit
       Obligation
0.25% decrease in discount rate
$
(1
)
 
$
130

 
$
1

 
$
37

0.25% increase in salary scale
2

 
14

 
—

 
—

1.00% increase in annual medical trend
—

 
—

 
3

 
44

1.00% decrease in annual medical trend
—

 
—

 
(3
)
 
(44
)

Other
Ameren sponsors a 401(k) plan for eligible employees. The Ameren 401(k) plan covered all eligible employees at December 31, 2015. The plan allows employees to contribute a portion of their compensation in accordance with specific guidelines. Ameren matches a percentage of the employee contributions up to certain limits. The following table presents the portion of the matching contribution to the Ameren 401(k) plan attributable to the continuing operations for each of the Ameren Companies for the years ended December 31, 2015, 2014, and 2013:
 
2015
 
2014
 
2013
Ameren Missouri
$
16

 
$
16

 
$
16

Ameren Illinois
12

 
11

 
10

Other
1

 
1

 
1

Ameren(a)
29

 
28

 
27

(a)
Includes amounts for Ameren registrant and nonregistrant subsidiaries.
Stock-Based Compensation
STOCK-BASED COMPENSATION
STOCK-BASED COMPENSATION
The 2014 Incentive Plan is Ameren’s long-term stock compensation plan for eligible employees and directors. The 2006 Incentive Plan was replaced prospectively for new grants beginning in April 2014. The 2014 Incentive Plan provides for a maximum of 8 million common shares to be available for grant to eligible employees and directors. To the extent that the issuance of a share that is subject to an outstanding award under the 2006 Incentive Plan would cause Ameren to exceed the maximum authorized shares under the 2006 Incentive Plan, the issuance of that share will take place under the 2014 Incentive Plan. This will reduce the maximum number of shares that may be granted under the 2014 Incentive Plan. The 2014 Incentive Plan awards may be stock options, stock appreciation rights, restricted stock, restricted stock units, performance shares, performance share units, cash-based awards, and other stock-based awards.
A summary of nonvested shares at December 31, 2015, and changes during the year ended December 31, 2015, under the 2006 Incentive Plan and the 2014 Incentive Plan are presented below:
  
Performance Share Units
  
Share
Units
 
Weighted-average
Fair Value per Share Unit
Nonvested at January 1, 2015
1,162,377

 
$
35.35

Granted(a)
570,313

 
52.88

Forfeitures
(1,944
)
 
34.75

Earned and vested(b)
(705,876
)
 
33.93

Nonvested at December 31, 2015
1,024,870

 
$
46.08

(a)
Includes performance share units (share units) granted to certain executive and nonexecutive officers and other eligible employees in 2015 under the 2014 Incentive Plan.
(b)
Includes share units granted in 2013 that vested as of December 31, 2015, that were earned pursuant to the terms of the award grants. Also includes share units that vested due to attainment of retirement eligibility by certain employees. Actual shares issued for retirement-eligible employees will vary depending on actual performance over the three-year measurement period.
Ameren recorded compensation expense of $19 million, $19 million, and $20 million for the years ended December 31, 2015, 2014, and 2013, respectively, and a related tax benefit of $7 million, $7 million, and $8 million for the years ended December 31, 2015, 2014, and 2013, respectively. Ameren settled performance share units of $27 million, $33 million, and $11 million for the years ended December 31, 2015, 2014, and 2013. There were no significant compensation costs capitalized related to the performance share units during the years ended December 31, 2015, 2014, and 2013. As of December 31, 2015, total compensation cost of $21 million related to nonvested awards not yet recognized is expected to be recognized over a weighted-average period of 23 months.
Performance Share Units
A share unit vests and entitles an employee to receive shares of Ameren common stock (plus accumulated dividends) if, at the end of the three-year performance period, certain specified performance or market conditions have been met and if the individual remains employed by Ameren through the required vesting period. The exact number of shares issued pursuant to a share unit varies from 0% to 200% of the target award, depending on actual company performance relative to the performance goals. The vesting period for share units awarded in 2015 extended beyond the three-year performance period to the payout date, while the vesting period for share units awarded in 2013 and 2014 matched the three-year performance period.
The fair value of each share unit awarded in 2015 under the 2014 Incentive Plan was determined to be $52.88, which was based on Ameren's closing common share price of $46.13 at December 31, 2014, and lattice simulations. Lattice simulations are used to estimate expected share payout based on Ameren's total shareholder return for a three-year performance period relative to the designated peer group beginning January 1, 2015. The simulations can produce a greater fair value for the share unit than the applicable closing common share price because they include the weighted payout scenarios in which an increase in the share price has occurred. The significant assumptions used to calculate fair value also included a three-year risk-free rate of 1.10%, volatility of 12% to 18% for the peer group, and Ameren's attainment of a three-year average earnings per share threshold during the performance period.
The fair value of each share unit awarded in 2014, excluding the grants issued in April 2014 for certain executive officers, under the 2006 Incentive Plan and the 2014 Incentive Plan was determined to be $38.90, which was based on Ameren’s closing common share price of $36.16 at December 31, 2013, and lattice simulations. Lattice simulations are used to estimate expected share payout based on Ameren’s total shareholder return for a three-year performance period relative to the designated peer group beginning January 1, 2014. The significant assumptions used to calculate fair value also included a three-year risk-free rate of 0.78%, volatility of 12% to 18% for the peer group, and Ameren’s attainment of a three-year average earnings per share threshold during the performance period.
Income Taxes
INCOME TAXES
INCOME TAXES
The following table presents the principal reasons for the difference between the effective income tax rate and the statutory federal income tax rate for the years ended December 31, 2015, 2014, and 2013:
 
Ameren Missouri
 
Ameren Illinois
 
Ameren
2015
 
 
 
 
 
Statutory federal income tax rate:
35
 %
 
35
 %
 
35
 %
Increases (decreases) from:
 
 
 
 
 
Depreciation differences
—

 
(2
)
 
(1
)
Amortization of investment tax credit
(1
)
 
—

 
(1
)
State tax
3

 
5

 
5

Other permanent items
—

 
(1
)
 
—

Effective income tax rate
37
 %
 
37
 %
 
38
 %
2014
 
 
 
 
 
Statutory federal income tax rate:
35
 %
 
35
 %
 
35
 %
Increases (decreases) from:
 
 
 
 
 
Amortization of investment tax credit
(1
)
 
—

 
(1
)
State tax
3

 
6

 
4

Other permanent items
—

 
—

 
1

Effective income tax rate
37
 %
 
41
 %
 
39
 %
2013
 
 
 
 
 
Statutory federal income tax rate:
35
 %
 
35
 %
 
35
 %
Increases (decreases) from:
 
 
 
 
 
Depreciation differences
—

 
(1
)
 
—

Amortization of investment tax credit
(1
)
 
—

 
(1
)
State tax
3

 
6

 
4

Other permanent items
1

 
—

 
—

Effective income tax rate
38
 %
 
40
 %
 
38
 %


The following table presents the components of income tax expense (benefit) for the years ended December 31, 2015, 2014, and 2013:
 
Ameren Missouri
 
Ameren Illinois
 
Other
 
Ameren
2015
 
 
 
 
 
 
 
Current taxes:
 
 
 
 
 
 
 
Federal
$
110

 
$
(83
)
 
$
(29
)
 
$
(2
)
State
17

 
(11
)
 
(10
)
 
(4
)
Deferred taxes:
 
 
 
 
 
 
 
Federal
71

 
193

 
35

 
299

State
16

 
29

 
31

 
76

Deferred investment tax credits, amortization
(5
)
 
(1
)
 
—

 
(6
)
Total income tax expense
$
209

 
$
127

 
$
27

 
$
363

2014
 
 
 
 
 
 
 
Current taxes:
 
 
 
 
 
 
 
Federal
$
(13
)
 
$
(51
)
 
$
27

 
$
(37
)
State
(3
)
 
(2
)
 
(32
)
 
(37
)
Deferred taxes:
 
 
 
 
 
 
 
Federal
222

 
159

 
(12
)
 
369

State
28

 
38

 
22

 
88

Deferred investment tax credits, amortization
(5
)
 
(1
)
 
—

 
(6
)
Total income tax expense
$
229

 
$
143

 
$
5

 
$
377

2013
 
 
 
 
 
 
 
Current taxes:
 
 
 
 
 
 
 
Federal
$
136

 
$
(15
)
 
$
(239
)
(a) 
$
(118
)
State
41

 
21

 
(43
)
(a) 
19

Deferred taxes:
 
 
 
 
 
 
 
Federal
64

 
99

 
205

(a) 
368

State
6

 
6

 
36

(a) 
48

Deferred investment tax credits, amortization
(5
)
 
(1
)
 
—

 
(6
)
Total income tax expense (benefit)
$
242

 
$
110

 
$
(41
)
 
$
311


(a)
These amounts are substantially related to the reversal of unrecognized tax benefits as a result of IRS guidance related to the deductibility of expenditures to maintain, replace, or improve steam or electric power generation property, along with casualty loss deductions for storm damage. The amounts also reflect the increase in deferred tax expense due to available net operating losses.
The Illinois corporate income tax rate was increased to 9.5% from January 2011 through December 2014. The tax rate decreased to 7.75% on January 1, 2015, and is scheduled to decrease to 7.3% on January 1, 2025.
The following table presents the deferred tax assets and deferred tax liabilities recorded as a result of temporary differences at December 31, 2015 and 2014:
 
Ameren Missouri
 
Ameren Illinois
 
Other
 
Ameren
2015
 
 
 
 
 
 
 
Accumulated deferred income taxes, net liability (asset):
 
 
 
 
 
 
 
Plant related
$
2,931

 
$
1,587

 
$
37

 
$
4,555

Regulatory assets, net
81

 
(1
)
 
—

 
80

Deferred employee benefit costs
(76
)
 
(40
)
 
(91
)
 
(207
)
Revenue requirement reconciliation adjustments

—

 
66

 
—

 
66

Tax carryforwards
(65
)
 
(133
)
 
(405
)
 
(603
)
Other
(27
)
 
1

 
20

 
(6
)
Total net accumulated deferred income tax liabilities (assets) (a)
$
2,844

 
$
1,480

 
$
(439
)
 
$
3,885

2014
 
 
 
 
 
 
 
Accumulated deferred income taxes, net liability (asset):
 
 
 
 
 
 
 
Plant related
$
2,776

 
$
1,393

 
$
16

 
$
4,185

Regulatory assets, net
82

 
(5
)
 
1

 
78

Deferred employee benefit costs
(80
)
 
(45
)
 
(95
)
 
(220
)
Revenue requirement reconciliation adjustments
—

 
66

 
3

 
69

Tax carryforwards
(107
)
 
(139
)
 
(429
)
 
(675
)
Other
86

 
(22
)
 
70

 
134

Total net accumulated deferred income tax liabilities (assets) (a)
$
2,757

 
$
1,248

 
$
(434
)
 
$
3,571


(a)
Reflects the adoption of the new authoritative accounting guidance for the balance sheet classification of deferred income taxes. See Note 1 – Summary of Significant Accounting Policies for additional information.
The following table presents the components of deferred tax assets relating to net operating loss carryforwards, tax credit carryforwards, and charitable contribution carryforwards at December 31, 2015:
 
Ameren Missouri
 
Ameren Illinois
 
Other
 
Ameren
Net operating loss carryforwards:
 
 
 
 
 
 
 
Federal(a)
$
35

 
$
127

 
$
245

 
$
407

State(b)
4

 
4

 
38

 
46

Total net operating loss carryforwards
$
39

 
$
131

 
$
283

 
$
453

Tax credit carryforwards:
 
 
 
 
 
 
 
Federal(c)
$
26

 
$
1

 
$
78

 
$
105

State(d)
—

 
1

 
40

 
41

State valuation allowance(e)
—

 
—

 
(2
)
 
(2
)
Total tax credit carryforwards
$
26

 
$
2

 
$
116

 
$
144

Charitable contribution carryforwards(f)
$
—

 
$
—

 
$
10

 
$
10

Valuation allowance(e)
—

 
—

 
(4
)
 
(4
)
Total charitable contribution carryforwards
$
—

 
$
—

 
$
6

 
$
6


(a)
Will begin to expire in 2029.
(b)
Will begin to expire in 2023.
(c)
Will begin to expire in 2029.
(d)
Will begin to expire in 2016.
(e)
See Schedule II under Part IV, Item 15, in this report for information on changes in the valuation allowance.
(f)
Will begin to expire in 2016.

The following table presents the components of deferred tax assets relating to net operating loss carryforwards, tax credit carryforwards, and charitable contribution carryforwards at December 31, 2014:
 
Ameren Missouri
 
Ameren Illinois
 
Other
 
Ameren
Net operating loss carryforwards:
 
 
 
 
 
 
 
Federal(a)
$
75

 
$
127

 
$
255

 
$
457

State(b)
11

 
10

 
53

 
74

Total net operating loss carryforwards
$
86

 
$
137

 
$
308

 
$
531

Tax credit carryforwards:
 
 
 
 
 
 
 
Federal(c)
$
21

 
$
1

 
$
77

 
$
99

State(d)
1

 
2

 
33

 
36

State valuation allowance(e)
(1
)
 
(1
)
 
(2
)
 
(4
)
Total tax credit carryforwards
$
21

 
$
2

 
$
108

 
$
131

Charitable contribution carryforwards(f)
$
—

 
$
—

 
$
19

 
$
19

Valuation allowance(e)
—

 
—

 
(6
)
 
(6
)
Total charitable contribution carryforwards
$
—

 
$
—

 
$
13

 
$
13


(a)
Will begin to expire in 2028
(b)
Will begin to expire in 2019.
(c)
Will begin to expire in 2029.
(d)
Began to expire in 2013.
(e)
See Schedule II under Part IV, Item 15, in this report for information on changes in the valuation allowance.
(f)
Began to expire in 2013.

Uncertain Tax Positions
A reconciliation of the change in the unrecognized tax benefit balance during the years ended December 31, 2013, 2014, and 2015, is as follows:
 
Ameren Missouri
 
Ameren Illinois
 
Other
 
Ameren
Unrecognized tax benefits – January 1, 2013
$
136

 
$
13

 
$
7

 
$
156

Increases based on tax positions prior to 2013
—

 
2

 
5

 
7

Decreases based on tax positions prior to 2013
(122
)
 
(16
)
 
(5
)
 
(143
)
Increases based on tax positions related to 2013
16

 
—

 
53

(a) 
69

Changes related to settlements with taxing authorities
—

 
—

 
—

 
—

Decreases related to the lapse of statute of limitations
1

 
—

 
—

 
1

Unrecognized tax benefits – December 31, 2013
$
31

 
$
(1
)
 
$
60

 
$
90

Increases based on tax positions prior to 2014
1

 
1

 
4

 
6

Decreases based on tax positions prior to 2014
(32
)
 
(1
)
 
(9
)
 
(42
)
Increases based on tax positions related to 2014
—

 
—

 
—

 
—

Changes related to settlements with taxing authorities
—

 
—

 
—

 
—

Increases related to the lapse of statute of limitations
—

 
—

 
—

 
—

Unrecognized tax benefits – December 31, 2014
$
—

 
$
(1
)
 
$
55

 
$
54

Increases based on tax positions prior to 2015
—

 
1

 
1

 
2

Decreases based on tax positions prior to 2015
—

 
—

 
(56
)
(a) 
(56
)
Increases based on tax positions related to 2015
—

 
—

 
—

 
—

Changes related to settlements with taxing authorities
—

 
—

 
—

 
—

Increases related to the lapse of statute of limitations
—

 
—

 
—

 
—

Unrecognized tax benefits – December 31, 2015
$
—

 
$
—

 
$
—

 
$
—

Total unrecognized tax benefits that, if recognized, would affect the effective tax rates as of December 31, 2013
$
3

 
$
—

 
$
51

(a) 
$
54

Total unrecognized tax benefits (detriments) that, if recognized, would affect the effective tax rates as of December 31, 2014
$
—

 
$
(1
)
 
$
53

(a) 
$
52

Total unrecognized tax benefits that, if recognized, would affect the effective tax rates as of December 31, 2015
$
—

 
$
—

 
$
—

 
$
—


(a)
Primarily due to tax positions relating to the New AER divestiture. The income statement impact of this unrecognized tax benefit was included in "Income (loss) from discontinued operations, net of taxes" on Ameren's consolidated statement of income (loss). See Note 16 – Divestiture Transactions and Discontinued Operations for additional information.
The Ameren Companies recognize interest charges (income) and penalties accrued on tax liabilities on a pretax basis as interest charges (income) or miscellaneous expense, respectively, in the statements of income.
A reconciliation of the change in the liability for interest on unrecognized tax benefits during the years ended December 31, 2013, 2014, and 2015, is as follows:
 
Ameren Missouri
 
Ameren Illinois
 
Other
 
Ameren
Liability for interest – January 1, 2013
$
8

 
$
1

 
$
(3
)
 
$
6

Interest charges (income) for 2013
(8
)
 
(1
)
 
4

 
(5
)
Liability for interest – December 31, 2013
$
—

 
$
—

 
$
1

 
$
1

Interest charges (income) for 2014
—

 
—

 
(1
)
 
(1
)
Liability for interest – December 31, 2014
$
—

 
$
—

 
$
—

 
$
—

Interest charges (income) for 2015
—

 
—

 
—

 
—

Liability for interest – December 31, 2015
$
—

 
$
—

 
$
—

 
$
—


As of December 31, 2013, 2014, and 2015, the Ameren Companies have accrued no amount for penalties with respect to unrecognized tax benefits.
In 2015, final settlements for tax years 2012 and 2013 were reached with the IRS. There were no uncertain tax positions related to the 2012 tax year, as of December 31, 2014, so this settlement did not affect the amount of recorded unrecognized tax benefits during 2015. The settlement related to the 2013 tax year resolved the uncertain tax position associated with the final tax basis of New AER and the related tax benefit resulting from the divested merchant generation business. The settlement resulted in a reduction of Ameren's unrecognized tax benefits of $53 million and an increase to net income from discontinued operations. See Note 16 – Divestiture Transactions and Discontinued Operations for additional information.

In 2014, final settlements for tax years 2007 through 2011 were reached with the IRS. These settlements, which resolved the uncertain tax positions associated with the timing of research tax deductions for these years, resulted in a decrease in Ameren’s and Ameren Missouri’s unrecognized tax benefits of $20 million, and $13 million, respectively. In addition, the settlement for tax years 2007 through 2011 provided certainty for the previously uncertain tax positions associated with the timing of research tax deductions for the remaining open tax years of 2012, 2013, and 2014. The certainty provided from the settlement resulted in an $18 million decrease in both Ameren’s and Ameren Missouri’s unrecognized tax benefits. The settlement also resulted in a $2 million increase to Ameren’s state unrecognized tax benefits. The net reduction in unrecognized tax benefits in 2014 did not materially affect income tax expense for the Ameren Companies.
In 2013, unrecognized tax benefits related to the deductibility of expenditures to maintain, replace, or improve steam or electric power generation property, along with casualty loss deductions for storm damage, were reduced by $103 million, $95 million, and $5 million for Ameren, Ameren Missouri, and Ameren Illinois, respectively. This reduction in unrecognized tax benefits did not affect income tax expense for the Ameren Companies. However, the liability for interest related to these unrecognized tax benefits was released in 2013. In 2013, Ameren adopted an accounting method change as a result of guidance issued by the IRS, with respect to the amount and timing of the deductions to maintain, replace, or improve generation property.
State income tax returns are generally subject to examination for a period of three years after filing. The state impact of any federal changes remains subject to examination by various states for up to one year after formal notification to the states. The Ameren Companies currently do not have material state income tax issues under examination, administrative appeals, or litigation.
Ameren Missouri has an uncertain tax position tracker. Under Missouri's regulatory framework, uncertain tax positions do not reduce Ameren Missouri's electric rate base. When an uncertain income tax position liability is resolved, the MoPSC requires, through the uncertain tax position tracker, the creation of a regulatory asset or regulatory liability to reflect the time value, using the weighted-average cost of capital included in each of the electric rate orders in effect before the tax position was resolved, of the difference between the uncertain tax position liability that was excluded from rate base and the final tax liability. The resulting regulatory asset or liability will affect earnings in the year it is created and then will be amortized over three years, beginning on the effective date of new rates established in the next electric rate case.
Related Party Transactions
RELATED PARTY TRANSACTIONS
RELATED PARTY TRANSACTIONS
In the normal course of business, the Ameren Companies have engaged in, and may in the future engage in, affiliate transactions. These transactions primarily consist of natural gas and power purchases and sales, services received or rendered, and borrowings and lendings. Transactions between affiliates are reported as intercompany transactions on their financial statements, but are eliminated in consolidation for Ameren’s financial statements. Below are the material related party agreements.
Electric Power Supply Agreements
Ameren Illinois must acquire capacity and energy sufficient to meet its obligations to customers. Ameren Illinois uses periodic RFP processes that are administered by the IPA and approved by the ICC, to contract capacity and energy on behalf of its customers. Ameren Missouri participates in the RFP process and has been a winning supplier for certain periods.
Capacity Supply Agreements
In 2010, Ameren Missouri contracted to supply a portion of Ameren Illinois’ capacity requirements for less than $1 million for the period from June 1, 2010, through May 31, 2013. In a procurement event in 2012, Ameren Missouri contracted to supply a portion of Ameren Illinois' capacity requirements for $1 million and $3 million for the 12 months ending May 31, 2014, and 2015, respectively. In a procurement event in 2015, Ameren Missouri contracted to supply a portion of Ameren Illinois' capacity requirements for $15 million for the 12 months ending May 31, 2017. 
Energy Swaps and Energy Products
As a result of an IPA procurement event in 2011, Ameren Missouri and Ameren Illinois entered into energy product agreements by which Ameren Missouri agreed to sell and Ameren Illinois agreed to purchase approximately 40,800 megawatthours at approximately $29 per megawatthour during the 12 months ended May 31, 2013, and approximately 40,800 megawatthours at approximately $28 per megawatthour during the 12 months ended May 31, 2014. The energy product agreements for the period ended May 31, 2013, were for off-peak hours only.
As a result of an IPA procurement event in 2014, Ameren Missouri and Ameren Illinois entered into energy product agreements by which Ameren Missouri agreed to sell and Ameren Illinois agreed to purchase approximately 168,400 megawatthours at approximately $51 per megawatthour during the period of January 1, 2015, through February 28, 2017.
As a result of an IPA procurement event in April 2015, Ameren Missouri and Ameren Illinois entered into energy product agreements by which Ameren Missouri agreed to sell and Ameren Illinois agreed to purchase 667,000 megawatthours at an average price of $36 per megawatthour during the period of June 1, 2015, through June 30, 2017. Also in September 2015, Ameren Missouri and Ameren Illinois entered into energy product agreements by which Ameren Missouri agreed to sell and Ameren Illinois agreed to purchase 339,000 megawatthours at an average price of $38 per megawatthour during the period of November 1, 2015, through May 31, 2018.
Interconnection and Transmission Agreements
Ameren Missouri and Ameren Illinois are parties to an interconnection agreement for the use of their respective transmission lines and other facilities for the distribution of power. These agreements have no contractual expiration date, but may be terminated by either party with three years’ notice.
Support Services Agreements
Ameren Services provides support services to its affiliates. The costs of support services, including wages, employee benefits, professional services, and other expenses, are based on, or are an allocation of, actual costs incurred. The support services agreement can be terminated at any time by the mutual agreement of Ameren Services and that affiliate or by either party with 60 days' notice before the end of a calendar year.
In addition, Ameren Missouri and Ameren Illinois provide affiliates, primarily Ameren Services, with access to their facilities for administrative purposes. The costs of the rent and facility services are based on, or are an allocation of, actual costs incurred.
Separately, Ameren Missouri and Ameren Illinois provide storm-related and miscellaneous support services to each other on an as-needed basis. 
Transmission Services
Ameren Illinois takes transmission service from MISO for the retail load it serves in the AMIL pricing zone. ATXI is one of the transmission owners in the AMIL pricing zone. Accordingly, ATXI receives transmission payments from Ameren Illinois through the MISO billing process.
Money Pool
See Note 4 – Short-term Debt and Liquidity and Note 5 – Long-term Debt and Equity Financings for a discussion of affiliate borrowing arrangements.
Collateral Postings
Under the terms of the Illinois power procurement agreements entered into through RFP processes administered by the IPA, suppliers must post collateral under certain market conditions to protect Ameren Illinois in the event of nonperformance. The collateral postings are unilateral, which means that only the suppliers can be required to post collateral. Therefore, Ameren Missouri, as a winning supplier in the RFP process, may be required to post collateral. As of December 31, 2015 and 2014, there were no collateral postings required of Ameren Missouri related to the Illinois power procurement agreements.
Tax Allocation Agreement
See Note 1 – Summary of Significant Accounting Policies for a discussion of the tax allocation agreement. At December 31, 2015 and 2014, Ameren Missouri accrued capital contributions from Ameren (parent) of $38 million and $9 million, respectively, pursuant to the tax allocation agreement.
The following table presents the impact on Ameren Missouri and Ameren Illinois of related party transactions for the years ended December 31, 2015, 2014, and 2013. It is based primarily on the agreements discussed above and the money pool arrangements discussed in Note 4 – Short-term Debt and Liquidity.
Agreement
Income Statement Line Item                    
 
  
 
Ameren
Missouri
 
Ameren
Illinois
Ameren Missouri power supply agreements
Operating Revenues
 
2015
$
15

$
(a)

with Ameren Illinois
 
 
2014
 
5

 
(a)

 
 
 
2013
 
3

 
(a)

Ameren Missouri and Ameren Illinois
Operating Revenues
 
2015
 
25

 
4

rent and facility services
 
 
2014
 
21

 
2

 
 
 
2013
 
21

 
1

Ameren Missouri and Ameren Illinois
Operating Revenues
 
2015
 
2

 
(b)

miscellaneous support services
 
 
2014
 
1

 
(b)

 
 
 
2013
 
1

 
3

Total Operating Revenues
 
 
2015
$
42

$
4

 
 
 
2014
 
27

 
2

 
 
 
2013
 
25

 
4

Ameren Illinois power supply
Purchased Power
 
2015
$
(a)

$
15

agreements with Ameren Missouri
 
 
2014
 
(a)

 
5

 
 
 
2013
 
(a)

 
3

Ameren Illinois transmission
Purchased Power
 
2015
 
(a)

 
2

services with ATXI
 
 
2014
 
(a)

 
2

 
 
 
2013
 
(a)

 
2

Total Purchased Power
 
 
2015
$
(a)

$
17

 
 
 
2014
 
(a)

 
7

 
 
 
2013
 
(a)

 
5

Ameren Services support services
Other Operations and
 
2015
$
131

$
119

agreement
Maintenance
 
2014
 
124

 
109

 
 
 
2013
 
116

 
93

Total Other Operations and
 
 
2015
$
131

$
119

Maintenance Expenses
 
 
2014
 
124

 
109

 
 
 
2013
 
116

 
93

Money pool borrowings (advances)
Interest (Charges)
 
2015
$
(b)

$
(b)

 
Income
 
2014
 
(b)

 
(b)

 
 
 
2013
 
(b)

 
(b)

(a)
Not applicable.
(b)
Amount less than $1 million.
Commitments And Contingencies
COMMITMENTS AND CONTINGENCIES
COMMITMENTS AND CONTINGENCIES
We are involved in legal, tax, and regulatory proceedings before various courts, regulatory commissions, authorities, and governmental agencies with respect to matters that arise in the ordinary course of business, some of which involve substantial amounts of money. We believe that the final disposition of these proceedings, except as otherwise disclosed in these notes to our financial statements, will not have a material adverse effect on our results of operations, financial position, or liquidity.
See also Note 1 – Summary of Significant Accounting Policies, Note 2 – Rate and Regulatory Matters, Note 10 – Callaway Energy Center, and Note 14 – Related Party Transactions in this report.
Callaway Energy Center
The following table presents insurance coverage at Ameren Missouri’s Callaway energy center at December 31, 2015. The property coverage and the nuclear liability coverage must be renewed on April 1 and January 1, respectively, of each year.
Type and Source of Coverage
Maximum Coverages
 
Maximum Assessments
 
Public liability and nuclear worker liability:
 
 
 
 
American Nuclear Insurers
$
375


$
—

 
Pool participation
13,114

(a)  
127

(b)  
 
$
13,489

(c)  
$
127

 
Property damage:
 
 
 
 
Nuclear Electric Insurance Limited
$
2,750

(d)  
$
27

(e)  
European Mutual Association for Nuclear Insurance
500

(f)  
—

 
 
$
3,250

 
$
27

 
Replacement power:
 
 
 
 
Nuclear Electric Insurance Limited
$
490

(g)  
$
10

(e)  

(a)
Provided through mandatory participation in an industrywide retrospective premium assessment program.
(b)
Retrospective premium under the Price-Anderson Act. This is subject to retrospective assessment with respect to a covered loss in excess of $375 million in the event of an incident at any licensed United States commercial reactor, payable at $19 million per year.
(c)
Limit of liability for each incident under the Price-Anderson liability provisions of the Atomic Energy Act of 1954, as amended. A company could be assessed up to $127 million per incident for each licensed reactor it operates, with a maximum of $19 million per incident to be paid in a calendar year for each reactor. This limit is subject to change to account for the effects of inflation and changes in the number of licensed reactors.
(d)
NEIL provides $2.25 billion in property damage, decontamination, and premature decommissioning insurance for both radiation and nonradiation events. An additional $500 million is provided for radiation events only for a total of $2.75 billion.
(e)
All NEIL-insured plants could be subject to assessments should losses exceed the accumulated funds from NEIL.
(f)
European Mutual Association for Nuclear Insurance provides $500 million in excess of the $2.75 billion and $2.25 billion property coverage for radiation and nonradiation events, respectively, provided by NEIL.
(g)
Provides replacement power cost insurance in the event of a prolonged accidental outage. Weekly indemnity is up to $4.5 million for 52 weeks, which commences after the first twelve weeks of an outage, plus up to $3.6 million per week for a minimum of 71 weeks thereafter, for a total not exceeding the policy limit of $490 million. Nonradiation events are sub-limited to $328 million.
The Price-Anderson Act is a federal law that limits the liability for claims from an incident involving any licensed United States commercial nuclear energy center. The limit is based on the number of licensed reactors. The limit of liability and the maximum potential annual payments are adjusted at least every five years for inflation to reflect changes in the Consumer Price Index. The most recent five-year inflationary adjustment became effective in September 2013. Owners of a nuclear reactor cover this exposure through a combination of private insurance and mandatory participation in a financial protection pool, as established by the Price-Anderson Act.
Losses resulting from terrorist attacks on nuclear facilities are covered under NEIL’s policies, subject to an industrywide aggregate policy coverage limit of $3.24 billion within a 12-month period, or $1.83 billion for events not involving radiation contamination.
If losses from a nuclear incident at the Callaway energy center exceed the limits of, or are not covered by, insurance or if coverage is unavailable, Ameren Missouri is at risk for any uninsured losses. If a serious nuclear incident were to occur, it could have a material adverse effect on Ameren’s and Ameren Missouri’s results of operations, financial position, and liquidity.
Leases
We lease various facilities, office equipment, plant equipment, and rail cars under capital and operating leases. The following table presents our lease obligations at December 31, 2015:
 
2016
 
2017
 
2018
 
2019
 
2020
 
After 5 Years
 
Total
Ameren:(a)
 
 
 
 
 
 
 
 
 
 
 
 
 
Minimum capital lease payments(b)
$
33

 
$
33

 
$
32

 
$
32

 
$
32

 
$
329

 
$
491

Less amount representing interest
27

 
27

 
26

 
25

 
25

 
73

 
203

Present value of minimum capital lease payments
$
6

 
$
6

 
$
6

 
$
7

 
$
7

 
$
256

 
$
288

Operating leases(c)
14

 
13

 
12

 
12

 
11

 
30

 
92

Total lease obligations
$
20

 
$
19

 
$
18

 
$
19

 
$
18

 
$
286

 
$
380

Ameren Missouri:
 
 
 
 
 
 
 
 
 
 
 
 
 
Minimum capital lease payments(b)
$
33

 
$
33

 
$
32

 
$
32

 
$
32

 
$
329

 
$
491

Less amount representing interest
27

 
27

 
26

 
25

 
25

 
73

 
203

Present value of minimum capital lease payments
$
6

 
$
6

 
$
6

 
$
7

 
$
7

 
$
256

 
$
288

Operating leases(c)
12

 
11

 
11

 
11

 
10

 
29

 
84

Total lease obligations
$
18

 
$
17

 
$
17

 
$
18

 
$
17

 
$
285

 
$
372

Ameren Illinois:
 
 
 
 
 
 
 
 
 
 
 
 
 
Operating leases(c)
$
1

 
$
1

 
$
1

 
$
1

 
$
1

 
$
1

 
$
6

(a)
Includes amounts for Ameren registrant and nonregistrant subsidiaries and intercompany eliminations.
(b)
See Properties under Part I, Item 2, and Note 3 – Property and Plant, Net, of this report for additional information.
(c)
Amounts related to certain land-related leases have indefinite payment periods. The annual obligations of $3 million, $2 million, and $1 million for Ameren, Ameren Missouri, and Ameren Illinois for these items are included in the 2016 through 2020 columns, respectively.
The following table presents total rental expense included in operating expenses for the years ended December 31, 2015, 2014, and 2013:
 
2015
 
2014
 
2013
Ameren(a)
$
36

 
$
37

 
$
32

Ameren Missouri
34

 
32

 
29

Ameren Illinois
28

 
25

 
21

(a)
Includes amounts for Ameren registrant and nonregistrant subsidiaries and intercompany eliminations.
Other Obligations
To supply a portion of the fuel requirements of our energy centers, we have entered into various long-term commitments for the procurement of coal, natural gas, nuclear fuel, and methane gas. We also have entered into various long-term commitments for purchased power and natural gas for distribution. The table below presents our estimated fuel, purchased power, and other commitments for fuel at December 31, 2015. Ameren’s and Ameren Missouri’s purchased power commitments include a 102-megawatt power purchase agreement with a wind farm operator, which expires in 2024. Ameren’s and Ameren Illinois’ purchased power commitments include the Ameren Illinois power purchase agreements entered into as part of the IPA-administered power procurement process. Included in the Other column are minimum purchase commitments under contracts for equipment, design and construction, and meter reading services at December 31, 2015.
 
Coal
 
Natural
Gas(a)
 
Nuclear
Fuel
 
Purchased
Power(b)
 
Methane
Gas
 
Other
 
Total
Ameren:(c)
 
 
 
 
 
 
 
 
 
 
 
 
 
2016
$
664

 
$
249

 
$
51

 
$
241

 
$
3

 
$
115

 
$
1,323

2017
685

 
190

 
46

 
147

 
4

 
73

 
1,145

2018
204

 
127

 
68

 
72

 
5

 
55

 
531

2019
110

 
89

 
24

 
58

 
5

 
56

 
342

2020
—

 
43

 
51

 
58

 
6

 
57

 
215

Thereafter
—

 
60

 
108

 
539

 
71

 
350

 
1,128

Total
$
1,663

 
$
758

 
$
348

 
$
1,115

 
$
94

 
$
706

 
$
4,684

Ameren Missouri:
 
 
 
 
 
 
 
 
 
 
 
 
 
2016
$
664

 
$
46

 
$
51

 
$
23

 
$
3

 
$
46

 
$
833

2017
685

 
36

 
46

 
23

 
4

 
32

 
826

2018
204

 
24

 
68

 
23

 
5

 
28

 
352

2019
110

 
14

 
24

 
23

 
5

 
29

 
205

2020
—

 
10

 
51

 
23

 
6

 
30

 
120

Thereafter
—

 
23

 
108

 
84

 
71

 
183

 
469

Total
$
1,663

 
$
153

 
$
348

 
$
199

 
$
94

 
$
348

 
$
2,805

Ameren Illinois:
 
 
 
 
 
 
 
 
 
 
 
 
 
2016
$
—

 
$
203

 
$
—

 
$
218

 
$
—

 
$
31

 
$
452

2017
—

 
154

 
—

 
124

 
—

 
25

 
303

2018
—

 
103

 
—

 
49

 
—

 
24

 
176

2019
—

 
75

 
—

 
35

 
—

 
27

 
137

2020
—

 
33

 
—

 
35

 
—

 
27

 
95

Thereafter
—

 
37

 
—

 
455

 
—

 
167

 
659

Total
$
—

 
$
605

 
$
—

 
$
916

 
$
—

 
$
301

 
$
1,822

(a)
Includes amounts for generation and for distribution.
(b)
The purchased power amounts for Ameren and Ameren Illinois include agreements through 2032 for renewable energy credits with various renewable energy suppliers. The agreements contain a provision that allows Ameren Illinois to reduce the quantity purchased in the event that Ameren Illinois would not be able to recover the costs associated with the renewable energy credits.
(c)
Includes amounts for Ameren registrant and nonregistrant subsidiaries.
Environmental Matters
We are subject to various environmental laws and regulations enforced by federal, state, and local authorities. From the beginning phases of siting and development to the operation of electric generation, transmission, and distribution facilities and natural gas storage, transmission, and distribution facilities, our activities involve compliance with diverse environmental laws and regulations. These laws and regulations address emissions, discharges to water, water usage, impacts to air, land, and water, and chemical and waste handling. Complex and lengthy processes are required to obtain and renew approvals, permits, and licenses for new, existing or modified facilities. Additionally, the use and handling of various chemicals or hazardous materials require release prevention plans and emergency response procedures.
The EPA has promulgated several environmental regulations that will have a significant impact on the electric utility industry. Over time, compliance with these regulations could be costly for certain companies, including Ameren Missouri, that operate coal-fired power plants. Significant new rules include the regulation of CO2 emissions from existing power plants through the Clean Power Plan and from new power plants through the revised NSPS; the CSAPR, which requires further reductions of SO2 emissions and NOx emissions from power plants; a regulation governing management and storage of CCR; the MATS, which require reduction of emissions of mercury, toxic metals, and acid gases from power plants; revised NSPS for particulate matter, SO2, and NOx emissions from new sources; new effluent standards applicable to wastewater discharges from power plants and new regulations under the Clean Water Act that could require significant capital expenditures, such as modifications to water intake structures or new cooling towers at Ameren Missouri’s energy centers. The EPA also periodically reviews and revises national ambient air quality standards, including those standards associated with emissions from power plants, such as particulate matter, ozone, SO2 and NOx. Certain of these new regulations are being or are likely to be challenged through litigation, so their ultimate implementation, as well as the timing of any such implementation, is uncertain. Although many details of future regulations are unknown, individually or the combined effects of new environmental regulations could result in significant capital expenditures and increased operating costs for Ameren and Ameren Missouri. Compliance with all of these environmental laws and regulations could be prohibitively expensive, result in the closure or alteration of the operation of some of Ameren Missouri’s energy centers, or require capital investment. Ameren and Ameren Missouri expect that these costs would be recoverable through rates, subject to MoPSC prudence review, but the nature and timing of costs could result in regulatory lag.
Ameren Missouri's current plan for compliance with existing environmental regulations for air emissions includes burning ultra-low-sulfur coal and installing new or optimizing existing pollution control equipment. Ameren and Ameren Missouri estimate that they will need to make capital expenditures of $600 million to $700 million in the aggregate from 2016 through 2020 in order to comply with existing environmental regulations. Ameren Missouri may be required to install additional air emissions controls within the next six to 10 years. This estimate includes our capital expenditures required for the CCR regulations that were published in 2015, the rule applicable to cooling water intake structures at existing power plants under the Clean Water Act, and the effluent limitation guidelines applicable to steam electric generating units under the Clean Water Act, all of which are discussed below. These estimates do not include the impacts of the Clean Power Plan discussed below. Considerable uncertainty remains in these estimates. The actual amount of capital expenditures required to comply with existing environmental regulations may vary substantially from the above estimate due to uncertainty as to the precise compliance strategies that will be used and their ultimate cost, among other things.
The following sections describe the more significant new environmental laws and rules and environmental enforcement and remediation matters that affect or could affect our operations.
Clean Air Act
Federal and state laws require significant reductions in SO2 and NOx through either emission source reductions or the use and retirement of emission allowances. The CSAPR became effective in 2015. There will be further emission reduction requirements in 2017 and potentially more in subsequent years. To achieve compliance with CSAPR, Ameren Missouri burns ultra-low-sulfur coal and operates two scrubbers at its Sioux energy center. Ameren Missouri does not expect to make additional capital investments to comply with the current CSAPR requirements. However, Ameren Missouri expects to incur additional costs as it lowers its emissions at one or more of its energy centers to comply with the CSAPR in future years. These higher costs are expected to be collected from customers through the FAC or higher base rates.
In December 2011, the EPA issued the MATS under the Clean Air Act, which requires reductions in emissions of mercury and other hazardous air pollutants, such as acid gases, trace metals, and hydrogen chloride. The MATS do not require a specific control technology to achieve the emission reductions. The MATS apply to each unit at a coal-fired power plant. However, in certain cases, compliance can be achieved by averaging emissions from similar units at the same power plant. Compliance was required by April 2015 or, with a case-by-case extension, by April 2016. All of Ameren Missouri's coal-fired power plants will be in compliance before the required due dates. As part of Ameren Missouri's compliance plan, the Meramec energy center will burn natural gas at two of its units beginning in April 2016, thereby excluding such units from the MATS. In addition, Ameren Missouri is incurring additional costs to comply with the MATS. These higher costs are being collected from customers through the FAC or higher base rates.
CO2 Emissions Standards
The Clean Power Plan, which sets forth CO2 emissions standards applicable to existing power plants, was issued by the EPA but stayed by the United States Supreme Court pending the outcome of various appeals, as discussed below.
If the Clean Power Plan is ultimately upheld as issued, Ameren Missouri expects to incur increased fuel and operating costs, and make new or accelerated capital expenditures, in addition to the costs of making modifications to existing operations in order to achieve compliance. The Clean Power Plan required Missouri and Illinois to reduce CO2 emissions from power plants within their states significantly below 2005 levels by 2030. The rule contains interim compliance periods commencing in 2022 that require each state to demonstrate progress in achieving its CO2 reduction target. Ameren is evaluating the Clean Power Plan's potential impacts to its operations, including those related to electric system reliability, and to its level of investment in customer energy efficiency programs, renewable energy, and other forms of generation investment. Significant uncertainty exists regarding the impact of the Clean Power Plan, as its implementation will depend upon plans to be developed by the states. Numerous legal challenges are pending, which could result in the rule being declared invalid or the nature and timing of CO2 emissions reductions being revised. In February 2016, the United States Supreme Court stayed the Clean Power Plan and all implementation requirements until such time as legal appeals are concluded. The District of Columbia Circuit Court of Appeals has scheduled hearings for June 2016 on the legality of the rule. A decision by the District of Columbia Circuit Court of Appeals is expected to be issued later this year and additional appeals before the United States Supreme Court are likely. Appeals are not expected to conclude prior to 2018. We cannot predict the outcome of such legal challenges or their impact on our results of operations, financial position, or liquidity. If the rule is ultimately upheld and implemented in substantially similar form to the rule when issued, compliance measures could result in the closure or alteration of the operation of some of Ameren Missouri’s coal and natural-gas-fired energy centers, which could result in increased operating costs. Ameren Missouri expects substantially all of these increased costs to be recoverable, subject to MoPSC prudence review, through higher rates to customers, which could be significant.
Also, in August 2015, the EPA issued final regulations that set CO2 emissions standards for new power plants. These new standards establish separate emissions limits for new natural-gas-fired combined cycle plants and new coal-fired plants.
Federal and state legislation or regulations that mandate limits on the emission of CO2 may result in significant increases in capital expenditures and operating costs, which could lead to increased liquidity needs and higher financing costs. Mandatory limits on the emission of CO2 could increase costs for Ameren Missouri’s customers or have a material adverse effect on Ameren's and Ameren Missouri's results of operations, financial position, and liquidity if regulators delay or deny recovery in rates of these compliance costs. The cost of Ameren Illinois’ purchased power and gas purchased for resale could increase. However, Ameren Illinois expects these costs would be recovered from customers with no material adverse effect on its results of operations, financial position, or liquidity. Ameren's and Ameren Missouri's earnings might benefit from increased investment to comply with CO2 emission limitations to the extent that the investments are reflected and recovered on a timely basis in rates charged to customers.
NSR and Clean Air Litigation
In January 2011, the Department of Justice, on behalf of the EPA, filed a complaint against Ameren Missouri in the United States District Court for the Eastern District of Missouri. The EPA's complaint, as amended in October 2013, alleges that in performing projects at its Rush Island coal-fired energy center in 2007 and 2010, Ameren Missouri violated provisions of the Clean Air Act and Missouri law. Ameren Missouri anticipates that a trial of this case could occur as early as 2016. Ameren Missouri believes its defenses are meritorious and is defending itself vigorously. However, there can be no assurances that it will be successful in its efforts.
The ultimate resolution of this matter could have a material adverse effect on the results of operations, financial position, and liquidity of Ameren and Ameren Missouri. A resolution of this matter could result in increased capital expenditures for the installation of pollution control equipment and increased operations and maintenance expenses. We are unable to predict the ultimate resolution of these matters or the costs that might be incurred.
Clean Water Act
In August 2014, the EPA issued its final rule applicable to cooling water intake structures at existing power plants. The rule requires a case-by-case evaluation and plan for reducing aquatic organisms impinged on the facility’s intake screens or entrained through the plant's cooling water system. All of Ameren Missouri’s coal-fired and nuclear energy centers are subject to this rule. Each of Ameren Missouri’s affected energy centers will become subject to the revised limitations when it renews its water discharge permit. These permits are scheduled to be renewed between 2018 and 2023. The rule could have an adverse effect on Ameren’s and Ameren Missouri’s results of operations, financial position, and liquidity if its implementation requires the installation of cooling towers or extensive modifications to the cooling water systems at our energy centers and if those investments are not recovered on a timely basis in electric rates charged to Ameren Missouri's customers.
In September 2015, the EPA issued its final rule under the Clean Water Act to revise the effluent limitation guidelines applicable to steam electric generating units. Effluent limitation guidelines are national standards for water discharges that are based on the effectiveness of available control technology. The EPA's rule prohibits effluent discharges of certain, but not all, waste streams and imposes more stringent limitations on certain components in water discharges from power plants. All of Ameren Missouri’s coal-fired energy centers are subject to this rule and its implementation will be consistent with the water discharge permit process described above beginning as early as 2018. Ameren Missouri is evaluating the final rule, which became effective in January 2016, and the possible effects on its operations.
Ash Management
In 2015, the EPA issued regulations regarding the management and disposal of CCR, that will affect future CCR disposal and handling costs at Ameren Missouri's energy centers. The regulations allow for the management of CCR as a solid waste, as well as for its continued beneficial uses, such as recycling, which could reduce the amount to be disposed. The regulations also establish criteria regarding the structural integrity, location, and operation of CCR impoundments and landfills. They require groundwater monitoring and closure of impoundments if the groundwater standards are not achieved. During 2015, Ameren and Ameren Missouri recorded an increase to their AROs associated with CCR storage facilities and accelerated the closure of certain CCR storage facilities at its energy centers as a result of the new regulations. Ameren Missouri plans to close these CCR storage facilities between 2018 and 2023. See Note 1 – Summary of Significant Accounting Policies in this report for additional information. Ameren Missouri's capital expenditure plan includes the cost of constructing landfills as part of its environmental compliance plan.
The new regulations do not apply to ash ponds at plants no longer in operation, such as Ameren’s Meredosia and Hutsonville energy centers.
Remediation
The Ameren Companies are involved in a number of remediation actions to clean up sites affected by hazardous substances, as required by federal and state law. Such laws require that responsible parties fund remediation actions regardless of their degree of fault, the legality of original disposal, or the ownership of a disposal site. Ameren Missouri and Ameren Illinois have each been identified by federal or state governments as a potentially responsible party at several contaminated sites.
As of December 31, 2015, Ameren Illinois owned or was otherwise responsible for 44 former MGP sites in Illinois, which are in various stages of investigation, evaluation, remediation, and closure. Ameren Illinois estimates it could substantially conclude remediation efforts by 2025. The ICC allows Ameren Illinois to recover remediation and litigation costs associated with its former MGP sites from its electric and natural gas utility customers through environmental adjustment rate riders. Costs are subject to annual prudence review by the ICC. As of December 31, 2015, Ameren Illinois estimated the obligation related to these former MGP sites at $232 million to $313 million. Ameren and Ameren Illinois recorded a liability of $232 million to represent their estimated minimum obligation for these sites, as no other amount within the range was a better estimate.
The scope and extent to which these former MGP sites are remediated may increase as remediation efforts continue. Considerable uncertainty remains in these estimates, as many factors can influence the ultimate actual costs, including site-specific unanticipated underground structures, the degree to which groundwater is encountered, regulatory changes, local ordinances, and site accessibility. The actual costs may vary substantially from these estimates.
Ameren Illinois formerly used an off-site landfill, which Ameren Illinois did not own, in connection with the operation of a previously owned energy center. Ameren Illinois could be required to perform certain maintenance activities at that landfill, which is now closed. As of December 31, 2015, Ameren Illinois estimated the obligation related to this site at $0.5 million to $6 million. Ameren Illinois recorded a liability of $0.5 million to represent its estimated minimum obligation for this site, as no other amount within the range was a better estimate. Ameren Illinois is also responsible for the cleanup of some underground storage tanks and a water treatment plant in Illinois. As of December 31, 2015, Ameren Illinois recorded a liability of $0.7 million to represent its best estimate of the obligation for these sites.
In 2008, the EPA issued an administrative order to Ameren Missouri pertaining to a former coal tar distillery in St. Louis, Missouri, operated by Koppers Company or its predecessor and successor companies. While Ameren Missouri is the current owner of the site, it did not conduct any of the manufacturing operations involving coal tar or its byproducts. Ameren Missouri, along with two other potentially responsible parties, have completed site investigation activities and have submitted their findings to the EPA. As of December 31, 2015, Ameren Missouri estimated its obligation at $2 million to $5 million. Ameren Missouri recorded a liability of $2 million to represent its estimated minimum obligation, as no other amount within the range was a better estimate.
Ameren Missouri also participated in the investigation of several sites located in Sauget, Illinois. In 2000, the EPA notified Ameren Missouri and numerous other companies, including Solutia, Inc., that former landfills and lagoons at those sites may contain soil and groundwater contamination. These sites are known as Sauget Area 2. From about 1926 until 1976, Ameren Missouri operated an energy center adjacent to Sauget Area 2. Ameren Missouri currently owns a parcel of property at Sauget Area 2 that was once used as a landfill.
In December 2013, the EPA issued its record of decision for Sauget Area 2 approving the investigation and the remediation alternatives recommended by the potentially responsible parties. Further negotiation among the potentially responsible parties will determine how to fund the implementation of the EPA-approved cleanup remedies. As of December 31, 2015, Ameren Missouri estimated its obligation related to Sauget Area 2 at $1 million to $2.5 million. Ameren Missouri recorded a liability of $1 million to represent its estimated minimum obligation, as no other amount within the range was a better estimate.
In December 2012, Ameren Missouri signed an administrative order with the EPA and agreed to investigate soil and groundwater conditions at an Ameren Missouri-owned substation in St. Charles, Missouri. As of December 31, 2015, Ameren Missouri estimated and recorded a $0.6 million liability related to the site. Although monitoring will continue for some time, no significant additional remediation measures are anticipated.
Our operations or those of our predecessor companies involve the use of, disposal of, and in appropriate circumstances, the cleanup of substances regulated under environmental laws. We are unable to determine whether such practices will result in future environmental commitments or will affect our results of operations, financial position, or liquidity.
Pumped-storage Hydroelectric Facility Breach
In December 2005, there was a breach of the upper reservoir at Ameren Missouri's Taum Sauk pumped-storage hydroelectric energy center. The breach resulted in significant flooding in the local area, which damaged a state park. Ameren Missouri had liability insurance coverage for the Taum Sauk incident, subject to certain limits and deductibles.
As of December 31, 2015, Ameren Missouri had an insurance receivable of $41 million. In February 2016, Ameren Missouri and an insurer that was providing Ameren Missouri with liability coverage on the date of the Taum Sauk incident reached a settlement that resulted in Ameren Missouri receiving $42 million. As a result of this settlement, the receivable was included in “Miscellaneous accounts and notes receivable” on Ameren’s and Ameren Missouri’s balance sheets as of December 31, 2015 whereas previously this receivable was included in “Other assets” on their respective balance sheets as of December 31, 2014.
Asbestos-related Litigation
Ameren, Ameren Missouri, and Ameren Illinois have been named, along with numerous other parties, in a number of lawsuits filed by plaintiffs claiming varying degrees of injury from asbestos exposure at our present or former energy centers. Most have been filed in the Circuit Court of Madison County, Illinois. The total number of defendants named in each case varies, with 75 as the average number of parties as of December 31, 2015. Each lawsuit seeks unspecified damages that, if awarded at trial, typically would be shared among the various defendants.
The following table presents the pending asbestos-related lawsuits filed against Ameren Missouri and Ameren Illinois as of December 31, 2015:
Ameren
Missouri
 
Ameren
Illinois
 
Total(a)
26
 
38
 
48

(a)
Total does not equal the sum of the subsidiary unit lawsuits because some of the lawsuits name multiple Ameren entities as defendants.
At December 31, 2015, Ameren, Ameren Missouri, and Ameren Illinois had liabilities of $8 million, $3 million, and $5 million, respectively, recorded to represent their best estimates of their obligations related to asbestos claims.
Ameren Illinois has a tariff rider to recover the costs of IP asbestos-related litigation claims, subject to the following terms: 90% of the cash expenditures in excess of the amount included in base electric rates is to be recovered from a trust fund that was established when Ameren acquired IP. At December 31, 2015, the trust fund balance was $22 million, including accumulated interest. If cash expenditures are less than the amount in base rates, Ameren Illinois will contribute 90% of the difference to the trust fund. Once the trust fund is depleted, 90% of allowed cash expenditures in excess of base rates will be recovered through charges assessed to customers under the tariff rider. The rider will permit recovery from electric customers within IP’s historical service territory.
Ameren Missouri Municipal Taxes
The cities of Creve Coeur and Winchester, Missouri, on behalf of themselves and other municipalities in Ameren Missouri’s service area, filed a class action lawsuit in November 2011 against Ameren Missouri in the Circuit Court of St. Louis County, Missouri. The lawsuit alleges that Ameren Missouri failed to collect and pay gross receipts taxes or license fees on certain revenues. Ameren and Ameren Missouri recorded immaterial liabilities on their respective balance sheets as of December 31, 2015, representing their estimate of taxes and fees due as a result of this lawsuit. The ultimate resolution of any unpaid municipal tax or fees could have a material adverse effect on the results of operations, financial position, and liquidity of Ameren and Ameren Missouri. Ameren Missouri believes its defenses are meritorious and is defending itself vigorously; however, there can be no assurances that Ameren Missouri will be successful in its efforts.
Divestiture Transactions and Discontinued Operations
DIVESTITURE TRANSACTIONS AND DISCONTINUED OPERATIONS
NOTE 16 – DIVESTITURE TRANSACTIONS AND DISCONTINUED OPERATIONS
On December 2, 2013, Ameren completed the divestiture of New AER to IPH in accordance with the transaction agreement between Ameren and IPH dated March 14, 2013, as amended by a letter agreement dated December 2, 2013. Pursuant to that agreement, in 2015, Ameren paid $25 million related to a previously-recorded liability and concluded its obligations to provide credit support to New AER with no resulting additional impact to its results of operations. The transaction agreement with IPH, as amended, provides that if the Elgin, Gibson City, and Grand Tower gas-fired energy centers are subsequently sold by Medina Valley and if Medina Valley receives additional proceeds from such sale, Medina Valley will pay Genco any proceeds from such sale, net of taxes and other expenses, in excess of the $137.5 million previously paid to Genco.
On January 31, 2014, Medina Valley completed the sale of the Elgin, Gibson City, and Grand Tower gas-fired energy centers to Rockland Capital for a total purchase price of $168 million. The agreement with Rockland Capital required a portion of the purchase price to be held in escrow until January 31, 2016, to fund certain indemnity obligations, if any, of Medina Valley. Medina Valley received the escrow balance from Rockland Capital and expects to pay Genco its portion of that escrow balance during the first quarter of 2016.
Discontinued Operations Presentation
All matters related to the final tax basis of New AER and the related tax benefit resulting from the divested merchant generation business have been resolved with the completion of the IRS audit for 2013. During 2015, based on the completion of the IRS audit, Ameren removed a reserve for unrecognized tax benefits recorded in 2013 and recognized a tax benefit from discontinued operations. See Note 13 – Income Taxes for additional information regarding the Ameren Companies’ uncertain tax positions.
The following table presents the components of discontinued operations in Ameren's consolidated statement of income (loss) for the years ended December 31, 2015, 2014, and 2013:
 
Year ended
 
 
2015
 
2014
 
2013
 
Operating revenues
$
—

 
$
1

 
$
1,037

 
Operating benefits (expenses)
1


(2
)
 
(1,207
)
(a) 
Operating income (loss)
1

 
(1
)
 
(170
)
 
Other income (loss)
—

 
—

 
(1
)
 
Interest charges
—

 
—

 
(39
)
 
Income (loss) before income taxes
1

 
(1
)
 
(210
)
 
Income tax (expense) benefit
50

 
—

 
(13
)
 
Income (loss) from discontinued operations, net of taxes
$
51

 
$
(1
)
 
$
(223
)
 
(a)
Includes a $201 million pretax loss on disposal relating to the New AER divestiture.
The following table presents the carrying amounts of the components of assets and liabilities of Ameren's discontinued operations, which consist primarily of AROs and related deferred income tax assets associated with the abandoned Meredosia and Hutsonville energy centers, at December 31, 2015 and 2014:
 
December 31, 2015
 
December 31, 2014
Assets of discontinued operations
 
 
 
Accumulated deferred income taxes, net
$
14

 
$
15

Total assets of discontinued operations
$
14

 
$
15

Liabilities of discontinued operations
 
 
 
Accounts payable and other current obligations
$
1

 
$
1

Asset retirement obligations(a)
28

 
32

Total liabilities of discontinued operations
$
29

 
$
33


(a)
Ameren is demolishing the Hutsonville energy center and expects to demolish the Meredosia energy center beginning in 2016.
Segment Information
SEGMENT INFORMATION
SEGMENT INFORMATION
Ameren has two reportable segments: Ameren Missouri and Ameren Illinois. Ameren Missouri and Ameren Illinois each have one reportable segment. The Ameren Missouri segment for both Ameren and Ameren Missouri includes all the operations of Ameren Missouri as described in Note 1 – Summary of Significant Accounting Policies. The Ameren Illinois segment for both Ameren and Ameren Illinois consists of all of the operations of Ameren Illinois as described in Note 1 – Summary of Significant Accounting Policies. The category called Other primarily includes Ameren parent company activities, Ameren Services, and ATXI. The Other category also includes certain corporate activities previously included in the Merchant Generation segment. See Note 16 – Divestiture Transactions and Discontinued Operations for additional information.
The following table presents information about the reported revenues and specified items reflected in Ameren’s net income attributable to Ameren common shareholders and capital expenditures from continuing operations for the years ended December 31, 2015, 2014, and 2013, and total assets in continuing operations as of December 31, 2015, 2014, and 2013:
 
Ameren
Missouri
 
Ameren
Illinois
 
Other
 
Intersegment
Eliminations
 
Consolidated
 
2015
 
 
 
 
 
 
 
 
 
 
External revenues
$
3,566

 
$
2,462

 
$
70

 
$
—

 
$
6,098

 
Intersegment revenues
43

 
4

 
2

 
(49
)
 
—

 
Depreciation and amortization
492

 
295

 
9

 
—

 
796

 
Interest and dividend income
28

 
12

 
1

 
—

 
41

 
Interest charges
219

 
131

 
5

 
—

 
355

 
Income taxes
209

 
127

 
27

 
—

 
363

 
Net income attributable to Ameren common shareholders from continuing operations
352

 
214

 
13

 
—

 
579

 
Capital expenditures
622

 
918

 
377

(a) 
—

 
1,917

 
Total assets(c)
13,851

 
8,903

 
1,139

 
(267
)
 
23,626

(b) 
2014
 
 
 
 
 
 
 
 
 
 
External revenues
$
3,526

 
$
2,496

 
$
31

 
$
—

 
$
6,053

 
Intersegment revenues
27

 
2

 
2

 
(31
)
 
—

 
Depreciation and amortization
473

 
263

 
9

 
—

 
745

 
Interest and dividend income
28

 
7

 
2

 
—

 
37

 
Interest charges
211

 
112

 
18

 
—

 
341

 
Income taxes
229

 
143

 
5

 
—

 
377

 
Net income (loss) attributable to Ameren common shareholders from continuing operations
390

 
201

 
(4
)
 
—

 
587

 
Capital expenditures
747

 
835

 
203

(a) 
—

 
1,785

 
Total assets(c)
13,474

 
8,204

 
799

 
(203
)
 
22,274

(b) 
2013
 
 
 
 
 
 
 
 
 
 
External revenues
$
3,516

 
$
2,307

 
$
15

 
$
—

 
$
5,838

 
Intersegment revenues
25

 
4

 
2

 
(31
)
 
—

 
Depreciation and amortization
454

 
243

 
9

 
—

 
706

 
Interest and dividend income
27

 
2

 
1

 
—

 
30

 
Interest charges
210

 
143

 
45

 
—

 
398

 
Income taxes (benefit)
242

 
110

 
(41
)
 
—

 
311

 
Net income (loss) attributable to Ameren common shareholders from continuing operations
395

 
160

 
(43
)
 
—

 
512

 
Capital expenditures
648

 
701

 
30

(a) 
—

 
1,379

 
Total assets(c)
12,867

 
7,397

 
711

 
(233
)
 
20,742

(b) 

(a)
Includes the elimination of intercompany transfers.
(b)
Excludes total assets from discontinued operations of $14 million, $15 million, and $165 million as of December 31, 2015, 2014, and 2013, respectively.
(c)
Reflects the adoption of the new authoritative accounting guidance for the presentation of debt issuance costs and balance sheet classification of deferred income taxes. See Note 1 – Summary of Significant Accounting Policies for additional information.
Selected Quarterly Information
SELECTED QUARTERLY INFORMATION
SELECTED QUARTERLY INFORMATION (Unaudited) (In millions, except per share amounts)
Ameren
2015
 
 
2014
Quarter ended(a)
March 31
 
June 30
 
September 30
 
December 31
 
 
March 31
 
June 30
 
September 30
 
December 31
Operating revenues
$
1,556

 
$
1,401

 
$
1,833

 
$
1,308

 
 
$
1,594

 
$
1,419

 
$
1,670

 
$
1,370

Operating income
256

 
237

 
626

 
140

 
 
246

 
322

 
561

 
125

Net income
110

 
151

 
345

 
30

 
 
98

 
150

 
295

 
49

Net income attributable to Ameren common shareholders – continuing operations
$
108

 
$
98

 
$
343

 
$
30

 
 
$
97

 
$
150

 
$
294

 
$
46

Net income (loss) attributable to Ameren common shareholders – discontinued operations
—

 
52

 
—

 
(1
)
 
 
(1
)
 
(1
)
 
(1
)
 
2

Net income attributable to Ameren common shareholders
$
108

 
$
150

 
$
343

 
$
29

 
 
$
96

 
$
149

 
$
293

 
$
48

Earnings per common share – basic – continuing operations
$
0.45

 
$
0.40

 
$
1.42

 
$
0.12

 
 
$
0.40

 
$
0.62

 
$
1.21

 
$
0.19

Earnings (loss) per common share – basic – discontinued operations
—

 
0.21

 
—

 
—

 
 
—

 
(0.01
)
 
—

 
0.01

Earnings per common share – basic
$
0.45

 
$
0.61

 
$
1.42

 
$
0.12

 
 
$
0.40

 
$
0.61

 
$
1.21

 
$
0.20

Earnings per common share – diluted – continuing operations
$
0.45

 
$
0.40

 
$
1.41

 
$
0.12

 
 
$
0.40

 
$
0.62

 
$
1.20

 
$
0.19

Earnings (loss) per common share – diluted – discontinued operations
—

 
0.21

 
—

 
—

 
 
—

 
(0.01
)
 
—

 
0.01

Earnings per common share – diluted
$
0.45

 
$
0.61

 
$
1.41

 
$
0.12

 
 
$
0.40

 
$
0.61

 
$
1.20

 
$
0.20

(a)
The sum of quarterly amounts, including per share amounts, may not equal amounts reported for year-to-date periods. This is because of the effects of rounding and the changes in the number of weighted-average diluted shares outstanding each period.
Ameren Missouri Quarter ended
 
Operating
Revenues
 
Operating
Income
 
Net Income
 (Loss)
 
Net Income (Loss)
Available
to Common
Shareholder
March 31, 2015
 
$
800

 
$
115

 
$
42

 
$
41

March 31, 2014
 
817

 
119

 
48

 
47

June 30, 2015
 
884

 
146

 
62

 
61

June 30, 2014
 
900

 
243

 
127

 
126

September 30, 2015
 
1,171

 
423

 
240

 
239

September 30, 2014
 
1,097

 
394

 
223

 
222

December 31, 2015
 
754

 
58

 
11

 
11

December 31, 2014
 
739

 
29

 
(5
)
 
(5
)

Ameren Illinois Quarter ended
 
Operating
Revenues
 
Operating
Income
 
Net Income
 
Net Income
Available
to Common
Shareholder
March 31, 2015
 
$
745

 
$
120

 
$
54

 
$
53

March 31, 2014
 
774

 
120

 
54

 
53

June 30, 2015
 
513

 
83

 
32

 
31

June 30, 2014
 
519

 
75

 
29

 
28

September 30, 2015
 
655

 
189

 
98

 
98

September 30, 2014
 
572

 
158

 
75

 
75

December 31, 2015
 
553

 
74

 
33

 
32

December 31, 2014
 
633

 
97

 
46

 
45

Schedule I - Condensed Financial Information Of Parent
Condensed Financial Information Of Parent
SCHEDULE I – CONDENSED FINANCIAL INFORMATION OF PARENT
AMEREN CORPORATION
CONDENSED STATEMENT OF INCOME AND COMPREHENSIVE INCOME
For the Years Ended December 31, 2015, 2014, and 2013
(In millions)
2015
 
2014
 
2013
Operating revenues
$
—

 
$
—

 
$
—

Operating expenses
14

 
11

 
26

Operating loss
(14
)
 
(11
)
 
(26
)
Equity in earnings of subsidiaries
600

 
607

 
546

Interest income from affiliates
6

 
3

 
3

Total other income (expense), net
(5
)
 
2

 
(5
)
Interest charges
3

 
16

 
42

Income tax (benefit)
5

 
(2
)
 
(36
)
Net Income Attributable to Ameren Common Shareholders – Continuing Operations
579

 
587

 
512

Net Income (Loss) Attributable to Ameren Common Shareholders
 – Discontinued Operations
51

 
(1
)
 
(223
)
Net Income Attributable to Ameren Common Shareholders
$
630

 
$
586

 
$
289

 
 
 
 
 
 
Net Income Attributable to Ameren Common Shareholders – Continuing Operations
$
579

 
$
587

 
$
512

Other Comprehensive Income, Net of Taxes:
 
 
 
 
 
Pension and other postretirement benefit plan activity, net of income taxes (benefit) of $3, $(7), and $16, respectively
6

 
(12
)
 
30

Comprehensive Income from Continuing Operations Attributable to Ameren Common Shareholders
585

 
575

 
542

Net Income (Loss) Attributable to Ameren Common Shareholders – Discontinued Operations
51

 
(1
)
 
(223
)
Other Comprehensive Loss from Discontinued Operations, Net of Income taxes
—

 
—

 
(19
)
Comprehensive Income (Loss) from Discontinued Operations Attributable to Ameren Common Shareholders
51

 
(1
)
 
(242
)
Comprehensive Income Attributable to Ameren Common Shareholders
$
636

 
$
574

 
$
300

SCHEDULE I – CONDENSED FINANCIAL INFORMATION OF PARENT
AMEREN CORPORATION
CONDENSED BALANCE SHEET
(In millions)
December 31, 2015
 
December 31, 2014
Assets:
 
 
 
Cash and cash equivalents
$
—

 
$
1

Advances to money pool
—

 
55

Accounts receivable – affiliates
53

 
28

Notes receivable – affiliates
—

 
94

Miscellaneous accounts and notes receivable
3

 
39

Other current assets
9

 
14

Total current assets
65

 
231

Investments in subsidiaries – continuing operations
7,231

 
6,680

Investment in subsidiary – discontinued operations
(4
)
 
(4
)
Note receivable – ATXI
290

 
100

Accumulated deferred income taxes, net
426

 
407

Other assets
158

 
152

Total assets
$
8,166

 
$
7,566

Liabilities and Shareholders’ Equity:
 
 
 
Short-term debt
301

 
585

Borrowings from money pool
14

 
—

Accounts payable – affiliates
75

 
88

Other current liabilities
22

 
52

Total current liabilities
412

 
725

Long-term debt
694

 
—

Pension and other postretirement benefits
33

 
47

Other deferred credits and liabilities
81

 
81

Total liabilities
1,220

 
853

Commitments and Contingencies (Notes 4 and 5)
 
 
 
Shareholders’ Equity:
 
 
 
Common stock, $.01 par value, 400.0 shares authorized – shares outstanding of 242.6
2

 
2

Other paid-in capital, principally premium on common stock
5,616

 
5,617

Retained earnings
1,331

 
1,103

Accumulated other comprehensive loss
(3
)
 
(9
)
Total shareholders’ equity
6,946

 
6,713

Total liabilities and shareholders’ equity
$
8,166

 
$
7,566

SCHEDULE I – CONDENSED FINANCIAL INFORMATION OF PARENT
AMEREN CORPORATION
CONDENSED STATEMENT OF CASH FLOWS
For the Years Ended December 31, 2015, 2014, and 2013
(In millions)
 
2015
 
2014
 
2013
Net cash flows provided by operating activities
 
$
537

 
$
514

 
$
453

Cash flows from investing activities:
 
 
 
 
 
 
Money pool advances, net
 
55

 
279

 
(371
)
Notes receivable – affiliates, net
 
(96
)
 
(134
)
 
(23
)
Investments in subsidiaries
 
(509
)
 
(280
)
 
(50
)
Distributions from subsidiaries
 
—

 
215

 
1

Proceeds from note receivable – Marketing Company
 
20

 
95

 
6

Contributions to note receivable – Marketing Company
 
(8
)
 
(89
)
 
(5
)
Other
 
(24
)
 
(12
)
 
(3
)
Net cash flows provided by (used in) investing activities
 
(562
)
 
74

 
(445
)
Cash flows from financing activities:
 
 
 
 
 
 
Dividends on common stock
 
(402
)
 
(390
)
 
(388
)
Short-term debt, net
 
(284
)
 
217

 
368

Money pool borrowings, net
 
14

 
—

 
—

Maturities of long-term debt
 
—

 
(425
)
 
—

Issuances of long-term debt
 
700

 
—

 
—

Capital issuance costs
 
(6
)
 
—

 
—

Other
 
2

 
—

 
—

Net cash flows provided by (used in) financing activities
 
24

 
(598
)
 
(20
)
Net change in cash and cash equivalents
 
$
(1
)
 
$
(10
)
 
$
(12
)
Cash and cash equivalents at beginning of year
 
1

 
11

 
23

Cash and cash equivalents at end of year
 
$
—

 
$
1

 
$
11

 
 
 
 
 
 
 
Cash dividends received from consolidated subsidiaries
 
$
575

 
$
340

 
$
570

 
 
 
 
 
 
 
Noncash investing activity – divestiture
 
$
—

 
$
—

 
$
494

Noncash investing activity – investments in subsidiaries
 
(38
)
 
(19
)
 
—

AMEREN CORPORATION (parent company only)
NOTES TO CONDENSED FINANCIAL STATEMENTS
December 31, 2015
NOTE 1 – BASIS OF PRESENTATION
Ameren Corporation (parent company only) is a public utility holding company that conducts substantially all of its business operations through its subsidiaries. In accordance with authoritative accounting guidance, Ameren Corporation (parent company only) has accounted for wholly owned subsidiaries using the equity method. These financial statements are presented on a condensed basis.
See Note 1 – Summary of Significant Accounting Policies under Part II, Item 8, of this report for additional information.
Accounting Changes and Other Matters
Presentation of Debt Issuance Costs
During 2015, the FASB issued authoritative accounting guidance requiring debt issuance costs to be presented as a reduction to the associated debt liability. Previously, debt issuance costs were presented in "Other assets" on Ameren Corporation's (parent company only) balance sheet. Ameren Corporation (parent company only) early adopted this standard in 2015. Retrospective application of the new guidance had no impact on Ameren Corporation's (parent company only) balance sheet at December 31, 2014. See Note 5 – Long-term Debt and Equity Financings under Part II, Item 8, of this report for additional information.
Balance Sheet Classification of Deferred Income Taxes
During 2015, the FASB issued authoritative accounting guidance requiring all deferred tax assets and liabilities, along with any related valuation allowances, to be classified as noncurrent on the balance sheet. Previously, the current portion of deferred taxes was presented as "Current accumulated deferred income taxes, net" and the noncurrent portion of deferred taxes was presented as "Accumulated deferred income taxes, net" on Ameren Corporation's (parent company only) balance sheet. Ameren Corporation (parent company only) early adopted this standard in 2015 and applied the guidance retrospectively. At December 31, 2014, the current portion of deferred income taxes of $143 million previously presented as "Current accumulated deferred income taxes, net" on Ameren Corporation's (parent company only) balance sheet was reclassified and presented in "Accumulated deferred income taxes, net" for comparative purposes.
Additional disclosures relating to the parent company financial statements are included within the combined notes under Part II, Item 8, of this report. See Note 1 – Summary of Significant Accounting Policies and Note 14 – Related Party Transactions under Part II, Item 8, of this report for information on the tax allocation agreement between Ameren Corporation (parent company only) and its subsidiaries.
NOTE 2 – SHORT-TERM DEBT AND LIQUIDITY
Ameren, Ameren Services, and other non-state-regulated Ameren subsidiaries have the ability, subject to Ameren parent company and applicable regulatory short-term borrowing authorizations, to access funding from the Credit Agreements and the commercial paper programs through a non-state-regulated subsidiary money pool agreement. All participants may borrow from or lend to the non-state-regulated money pool. The total amount available to pool participants from the non-state-regulated subsidiary money pool at any given time is reduced by the amount of borrowings made by participants, but is increased to the extent that the pool participants advance surplus funds to the non-state-regulated subsidiary money pool or remit funds from other external sources. The non-state-regulated subsidiary money pool was established to coordinate and to provide short-term cash and working capital for the participants. Participants receiving a loan under the non-state-regulated subsidiary money pool agreement must repay the principal amount of such loan, together with accrued interest. The rate of interest depends on the composition of internal and external funds in the non-state-regulated subsidiary money pool. Interest revenues and interest charges related to non-state-regulated money pool advances and borrowings were immaterial in 2014 and 2015.
Ameren Corporation (parent company only) had a total of $36 million in guarantees outstanding primarily for ATXI that were not recorded on its December 31, 2015 balance sheet. The ATXI guarantees were issued to local governments as assurance for potential remediation of damage caused by ATXI construction.
See Note 4 – Short-term Debt and Liquidity under Part II, Item 8, of this report for a description and details of short-term debt and liquidity needs of Ameren Corporation (parent company only).
NOTE 3 – LONG-TERM OBLIGATIONS
In November 2015, Ameren Corporation (parent company only) issued $350 million of 2.70% senior unsecured notes due November 15, 2020, with interest payable semiannually on May 15 and November 15 of each year, beginning May 15, 2016. Ameren (parent) received proceeds of $348 million, which were used to repay a portion of short-term debt.
In November 2015, Ameren Corporation (parent company only) issued $350 million of 3.65% senior unsecured notes due February 15, 2026, with interest payable semiannually on February 15 and August 15 of each year, beginning February 15, 2016. Ameren (parent) received proceeds of $347 million, which were used to repay a portion of short-term debt.
In May 2014, Ameren Corporation (parent company only) repaid at maturity $425 million of its 8.875% senior unsecured notes, plus accrued interest. The notes were repaid with proceeds from commercial paper issuances.
See Note 5 – Long-term Debt and Equity Financings under Part II, Item 8, of this report for additional information on Ameren Corporation's (parent company only) long-term debt.
NOTE 4 – COMMITMENTS AND CONTINGENCIES
See Note 15 – Commitments and Contingencies under Part II, Item 8, of this report for a description of all material contingencies of Ameren Corporation (parent company only).
NOTE 5 – DIVESTITURE TRANSACTIONS AND DISCONTINUED OPERATIONS
On December 2, 2013, Ameren completed the divestiture of New AER to IPH in accordance with the transaction agreement between Ameren and IPH dated March 14, 2013, as amended by a letter agreement dated December 2, 2013. As a result of the divestiture in 2013, Ameren Corporation (parent company only) recorded a pretax loss on disposal of $201 million. This charge was included within "Net Loss Attributable to Ameren Common Shareholders – Discontinued Operations" in the Ameren Corporation (parent company only) Condensed Statement of Income (Loss) and Comprehensive Income (Loss) for the year ended December 31, 2013.
During 2015, based on the completion of the IRS audit, Ameren Corporation (parent company only) removed a $53 million reserve for unrecognized tax benefits recorded in 2013 and recognized a tax benefit from discontinued operations. See Note 13 – Income Taxes under Part II, Item 8, of this report for additional information regarding Ameren Corporation's (parent company only) uncertain tax positions.
In 2015, Ameren paid $25 million related to a previously-recorded liability pursuant to the transaction agreement between Ameren and IPH with no resulting additional impact to its results of operations.
See Note 16 – Divestiture Transactions and Discontinued Operations under Part II, Item 8, of this report for additional information regarding the divestiture transactions and discontinued operations.
Schedule II - Valuation And Qualifying Accounts
Valuation And Qualifying Accounts
SCHEDULE II – VALUATION AND QUALIFYING ACCOUNTS
FOR THE YEARS ENDED DECEMBER 31, 2015, 2014, AND 2013
(in millions)
 
 
 
 
 
 
 
 
 
Column A
Column B
 
Column C
 
Column D
 
Column E
Description
Balance at
Beginning
of Period
 
(1)
Charged to Costs
and Expenses
 
(2)
Charged to Other
Accounts(a)
 
Deductions(b)
 
Balance at End
of Period
Ameren:
 
 
 
 
 
 
 
 
 
Deducted from assets – allowance for doubtful accounts:
 
 
 
 
 
 
 
 
 
2015
$
21

 
$
33

 
$
5

 
$
40

 
$
19

2014
18

 
36

 
4

 
37

 
21

2013
17

 
35

 
4

 
38

 
18

Deferred tax valuation allowance:
 
 
 
 
 
 
 
 
 
2015
$
10

 
$
4

 
$
(8
)
 
$
—

 
$
6

2014
7

 
3

 
—

 
—

 
10

2013
2

 
5

 
—

 
—

 
7

Ameren Missouri:
 
 
 
 
 
 
 
 
 
Deducted from assets – allowance for doubtful accounts:
 
 
 
 
 
 
 
 
 
2015
$
8

 
$
13

 
$
—

 
$
14

 
$
7

2014
5

 
16

 
—

 
13

 
8

2013
5

 
16

 
—

 
16

 
5

Deferred tax valuation allowance:
 
 
 
 
 
 
 
 
 
2015
$
1

 
$
—

 
$
(1
)
 
$
—

 
$
—

2014
1

 
—

 
—

 
—

 
1

2013
1

 
—

 
—

 
—

 
1

Ameren Illinois:
 
 
 
 
 
 
 
 
 
Deducted from assets – allowance for doubtful accounts:
 
 
 
 
 
 
 
 
 
2015
$
13

 
$
20

 
$
5

 
$
26

 
$
12

2014
13

 
20

 
4

 
24

 
13

2013
12

 
19

 
4

 
22

 
13

Deferred tax valuation allowance:
 
 
 
 
 
 
 
 
 
2015
$
1

 
$
—

 
$
(1
)
 
$
—

 
$
—

2014
1

 
—

 
—

 
—

 
1

2013
1

 
—

 
—

 
—

 
1

(a)
Amounts associated with the allowance for doubtful accounts relate to the uncollectible account reserve associated with receivables purchased by Ameren Illinois from alternative retail electric suppliers, as required by the Illinois Public Utilities Act. The amounts relating to the deferred tax valuation allowance are for items that have expired and were removed from both the underlying accumulated deferred income tax account as well as the offsetting valuation account.
(b)
Uncollectible accounts charged off, less recoveries.
Summary Of Significant Accounting Policies (Policy)
General 
Ameren, headquartered in St. Louis, Missouri, is a public utility holding company under PUHCA 2005. Ameren’s primary assets are its equity interests in its subsidiaries, including Ameren Missouri and Ameren Illinois. Ameren’s subsidiaries are separate, independent legal entities with separate businesses, assets, and liabilities. Dividends on Ameren’s common stock and the payment of expenses by Ameren depend on distributions made to it by its subsidiaries. Ameren’s principal subsidiaries are listed below.
•
Union Electric Company, doing business as Ameren Missouri, operates a rate-regulated electric generation, transmission, and distribution business and a rate-regulated natural gas transmission and distribution business in Missouri. Ameren Missouri was incorporated in Missouri in 1922 and is successor to a number of companies, the oldest of which was organized in 1881. It is the largest electric utility in the state of Missouri. It supplies electric and natural gas service to a 24,000-square-mile area in central and eastern Missouri. This area has an estimated population of 2.8 million and includes the Greater St. Louis area. Ameren Missouri supplies electric service to 1.2 million customers and natural gas service to 0.1 million customers.
•
Ameren Illinois Company, doing business as Ameren Illinois, operates rate-regulated electric and natural gas transmission and distribution businesses in Illinois. Ameren Illinois was created by the merger of CILCO and IP with and into CIPS in 2010. CIPS was incorporated in Illinois in 1923 and was the successor to a number of companies, the oldest of which was organized in 1902. Ameren Illinois supplies electric and natural gas utility service to portions of central and southern Illinois having an estimated population of 3.1 million in an area of 40,000 square miles. Ameren Illinois supplies electric service to 1.2 million customers and natural gas service to 0.8 million customers.
Ameren has various other subsidiaries that conduct activities such as the provision of shared services. Ameren also has a subsidiary, ATXI, that operates a FERC rate-regulated electric transmission business. ATXI is developing MISO-approved electric transmission projects, including the Illinois Rivers, Spoon River, and Mark Twain projects. Ameren is also pursuing projects to improve electric transmission system reliability within Ameren Missouri's and Ameren Illinois' service territories as well as competitive electric transmission investment opportunities outside of these territories, including investments outside of MISO.
Consolidation 
Ameren's financial statements are prepared on a consolidated basis, and therefore include the accounts of its majority-owned subsidiaries. Ameren Missouri and Ameren Illinois have no subsidiaries and therefore their financial statements are not prepared on a consolidated basis. All intercompany transactions have been eliminated. All tabular dollar amounts are in millions, unless otherwise indicated.
Our accounting policies conform to GAAP. Our financial statements reflect all adjustments (which include normal, recurring adjustments) that are necessary, in our opinion, for a fair presentation of our results. The preparation of financial statements in conformity with GAAP requires management to make certain estimates and assumptions. Such estimates and assumptions affect reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the dates of financial statements, and the reported amounts of revenues and expenses during the reported periods. Actual results could differ from those estimates.
Public Utilities 
Regulation
We are regulated by the MoPSC, the ICC, and the FERC. We defer certain costs as assets pursuant to actions of rate regulators or because of expectations that we will be able to recover such costs in future rates charged to customers. We also defer certain amounts as liabilities pursuant to actions of rate regulators or based on the expectation that such amounts will be returned to customers in future rates. Regulatory assets and liabilities are amortized consistent with the period of expected regulatory treatment. In addition to the cost recovery mechanisms discussed in the Purchased Gas, Power, and Fuel Rate-adjustment Mechanisms section below, Ameren Missouri and Ameren Illinois have approvals from rate regulators to use other cost recovery mechanisms. Ameren Missouri has a pension and postretirement benefit cost tracker, an uncertain tax positions tracker, a renewable energy standards cost tracker, a solar rebate program tracker, and the MEEIA energy efficiency rider. Ameren Illinois' and ATXI's electric transmission rates are determined pursuant to formula ratemaking. Additionally, Ameren Illinois' electric distribution business participates in the performance-based formula ratemaking process established pursuant to the IEIMA. Ameren Illinois also has an environmental cost rider, an asbestos-related litigation rider, an energy efficiency rider, a QIP rider, a VBA rider, and a bad debt rider. See Note 2 – Rate and Regulatory Matters for additional information on regulatory assets and liabilities.
Purchased Gas, Power and Fuel Rate-adjustment Mechanisms
Ameren Missouri and Ameren Illinois have various rate-adjustment mechanisms in place that provide for the recovery of purchased natural gas and electric fuel and purchased power costs without a traditional rate case proceeding. See Note 2 – Rate and Regulatory Matters for the regulatory assets and liabilities recorded at December 31, 2015 and 2014, related to the rate-adjustment mechanisms discussed below.
In Ameren Missouri’s and Ameren Illinois’ natural gas utility jurisdictions, changes in natural gas costs are reflected in billings to their natural gas utility customers through PGA clauses. The difference between actual natural gas costs and costs billed to customers in a given period is deferred as a regulatory asset or liability. The deferred amount is either billed or refunded to natural gas utility customers in a subsequent period.
In Ameren Illinois’ retail electric utility jurisdiction, changes in purchased power and transmission service costs are reflected in billings to its electric utility customers through pass-through rate-adjustment clauses. The difference between actual purchased power and transmission service costs and costs billed to customers in a given period is deferred as a regulatory asset or liability. The deferred amount is either billed or refunded to electric utility customers in a subsequent period.
Ameren Missouri has a FAC that allows an adjustment of electric rates three times per year for a pass-through to customers of 95% of changes in fuel and purchased power costs, including transportation charges and revenues, net of off-system sales, greater or less than the amount set in base rates, subject to MoPSC prudence review. The difference between the actual amounts incurred for these items and the amounts recovered from Ameren Missouri customers' base rates is deferred as a regulatory asset or liability. The deferred amounts are either billed or refunded to electric utility customers in a subsequent period. As of May 30, 2015, transmission revenues and substantially all transmission charges are excluded from net energy costs as a result of the April 2015 MoPSC electric rate order.
Environmental Costs
Liabilities for environmental costs are recorded on an undiscounted basis when it is probable that a liability has been incurred and the amount of the liability can be reasonably estimated. Costs are expensed or deferred as a regulatory asset when it is expected that the costs will be recovered from customers in future rates.
Cash and Cash Equivalents 
Cash and Cash Equivalents
Cash and cash equivalents include cash on hand and temporary investments purchased with an original maturity of three months or less.
Allowance for Doubtful Accounts Receivable 
Allowance for Doubtful Accounts Receivable
The allowance for doubtful accounts represents our estimate of existing accounts receivable that will ultimately be uncollectible. The allowance is calculated by applying estimated loss factors to various classes of outstanding receivables, including unbilled revenue. The loss factors used to estimate uncollectible accounts are based upon both historical collections experience and management’s estimate of future collections success given the existing and anticipated future collections environment. Ameren Illinois has a bad debt rider that adjusts rates for net write-offs of customer accounts receivable above or below those being collected in rates.
Materials and Supplies 
Materials and supplies are recorded at the lower of cost or market. Cost is determined by the average-cost method. Materials and supplies are capitalized as inventory when purchased and then expensed or capitalized as plant assets when installed, as appropriate.
Property and Plant 
Property and Plant, Net
We capitalize the cost of additions to and betterments of units of property and plant. The cost includes labor, material, applicable taxes, and overhead. An allowance for funds used during construction, as discussed below, is also capitalized as a cost of our rate-regulated assets. Maintenance expenditures, including nuclear refueling and maintenance outages, are expensed as incurred. When units of depreciable property are retired, the original costs, less salvage values, are charged to accumulated depreciation. If environmental expenditures are related to assets currently in use, as in the case of the installation of pollution control equipment, the cost is capitalized and depreciated over the expected life of the asset. See Asset Retirement Obligations below and Note 3 – Property and Plant, Net, for additional information.
Depreciation
Depreciation is provided over the estimated lives of the various classes of depreciable property by applying composite rates on a straight-line basis to the cost basis of such property. The provision for depreciation for the Ameren Companies in 2015, 2014, and 2013 ranged from 3% to 4% of the average depreciable cost.
Allowance for Funds Used During Construction 
Allowance for Funds Used During Construction
We capitalize allowance for funds used during construction, or the cost of borrowed funds and the cost of equity funds (preferred and common shareholders’ equity) applicable to rate-regulated construction expenditures, in accordance with the utility industry's accounting practice. Allowance for funds used during construction does not represent a current source of cash funds. This accounting practice offsets the effect on earnings of the cost of financing during construction, and it treats such financing costs in the same manner as construction charges for labor and materials.
Under accepted ratemaking practice, cash recovery of allowance for funds used during construction and other construction costs occurs when completed projects are placed in service and reflected in customer rates.
Goodwill 
Goodwill represents the excess of the purchase price of an acquisition over the fair value of the net assets acquired. Ameren and Ameren Illinois' carrying amount of goodwill was $411 million at December 31, 2015, and 2014. All of Ameren's and Ameren Illinois' goodwill at December 31, 2015 and 2014, was assigned to the Ameren Illinois reporting unit.
We evaluate goodwill for impairment as of October 31 each year, or more frequently if events and circumstances change that would more likely than not reduce the fair value of the Ameren Illinois reporting unit below its carrying amount. Entities assessing goodwill for impairment have the option of first performing a qualitative assessment before calculating the fair value of the reporting unit. If an entity determines, on the basis of qualitative factors, that the fair value of the reporting unit is more likely than not less than the carrying amount, a two-step quantitative test is required. An entity has the option to bypass the qualitative assessment in any period and proceed directly to the first step of the quantitative test, which compares the fair value of the reporting unit to its carrying amount. If the carrying amount of the reporting unit exceeds its estimated fair value, the entity performs the second step, which requires an assignment of the reporting unit's fair value to the individual assets and liabilities in order to determine the implied fair value of the reporting unit's goodwill. If the implied fair value of goodwill is less than its carrying amount, an impairment loss is recorded.
Ameren and Ameren Illinois elected to bypass the qualitative assessment and completed the first step of the quantitative test as of October 31, 2015. Based on the results, Ameren and Ameren Illinois determined that the estimated fair value of the Ameren Illinois reporting unit significantly exceeded its carrying value as of October 31, 2015, indicating no impairment of Ameren’s or Ameren Illinois’ goodwill. Ameren's and Ameren Illinois' valuation approach is based on a market participant view. It uses a weighted combination of a discounted cash flow analysis and a market multiples analysis. Significant assumptions used in estimating the fair value of the Ameren Illinois reporting unit include discount and growth rates, utility sector market performance and transactions, and projected operating results and cash flows.
The goodwill assigned to the Ameren Illinois reporting unit on the December 31, 2015 balance sheets of Ameren and Ameren Illinois had no accumulated goodwill impairment losses. Ameren and Ameren Illinois will continue to monitor internal and external factors for signs of possible declines in estimated fair value and potential goodwill impairment.
Impairment of Long-lived Assets 
We evaluate long-lived assets classified as held and used for impairment when events or changes in circumstances indicate that the carrying value of such assets may not be recoverable. Whether an impairment has occurred is determined by comparing the estimated undiscounted cash flows attributable to the assets to the carrying value of the assets. If the carrying value exceeds the undiscounted cash flows, we recognize an impairment charge equal to the amount by which the carrying value exceeds the estimated fair value of the assets. In the period in which we determine an asset meets held for sale criteria, we record an impairment charge to the extent the book value exceeds its estimated fair value less cost to sell. We did not identify any events or changes in circumstances that indicated that the carrying value of long-lived assets may not be recoverable in 2015 and 2014.
Asset Retirement Obligations 
Asset Retirement Obligations
We are required to record the estimated fair value of legal obligations associated with the retirement of tangible long-lived assets in the period in which the liabilities are incurred and to capitalize a corresponding amount as part of the book value of the related long-lived asset. In subsequent periods, we are required to make adjustments to AROs based on changes in the estimated fair values of the obligations. Corresponding increases in asset book values are depreciated over the remaining useful life of the related asset. Uncertainties as to the probability, timing, or amount of cash expenditures associated with AROs affect our estimates of fair value. Ameren and Ameren Missouri have recorded AROs for retirement costs associated with Ameren Missouri’s Callaway energy center decommissioning costs, CCR facilities, and river structures. Also, Ameren, Ameren Missouri, and Ameren Illinois have recorded AROs for retirement costs associated with asbestos removal and the disposal of certain transformers. Ameren and Ameren Missouri have a nuclear decommissioning trust fund for the decommissioning of the Callaway energy center. Asset removal costs accrued by our rate-regulated operations that do not constitute legal obligations are classified as regulatory liabilities. See Note 2 – Rate and Regulatory Matters.
Noncontrolling Interest 
Noncontrolling Interests
As of December 31, 2015 and 2014, Ameren’s noncontrolling interests included the preferred stock of Ameren Missouri and Ameren Illinois.
Revenue 
Operating Revenue
The Ameren Companies record operating revenue for electric or natural gas service when it is delivered to customers. We accrue an estimate of electric and natural gas revenues for service rendered but unbilled at the end of each accounting period.
Ameren Illinois participates in the performance-based formula ratemaking framework pursuant to the IEIMA. In addition, Ameren Illinois' and ATXI's electric transmission delivery service operating revenues are regulated by the FERC. The provisions of the IEIMA and the FERC's electric transmission formula rate framework provide for annual reconciliations of the electric delivery and electric transmission service revenue requirements necessary to reflect the actual recoverable costs incurred in a given year with the revenue requirements in customer rates for that year, including an allowed return on equity. In each of those electric jurisdictions, if the current year's revenue requirement is greater than the revenue requirement reflected in that year's customer rates, an increase to electric operating revenues with an offset to a regulatory asset is recorded to reflect the expected recovery of those additional amounts from customers within the next two years. In each jurisdiction, if the current year's revenue requirement is less than the revenue requirement reflected in that year's customer rates, a reduction to electric operating revenues with an offset to a regulatory liability is recorded to reflect the expected refund to customers within the next two years. See Note 2 – Rate and Regulatory Matters for information regarding Ameren Illinois' revenue requirement reconciliation pursuant to the IEIMA.
Cost Of Sales 
Nuclear Fuel
Ameren Missouri’s cost of nuclear fuel is capitalized and then amortized to fuel expense on a unit-of-production basis. The cost is charged to "Operating Expenses – Fuel" in the statement of income.
Accounting for MISO Transactions
MISO-related purchase and sale transactions are recorded by Ameren, Ameren Missouri, and Ameren Illinois using settlement information provided by MISO. Ameren Missouri records these purchase and sale transactions on a net hourly position. Ameren Missouri records net purchases in a single hour in “Operating Expenses – Purchased power” and net sales in a single hour in “Operating Revenues – Electric” in its statement of income. Ameren Illinois records net purchases in “Operating Expenses – Purchased power” in its statement of income to reflect all of its MISO transactions relating to the procurement of power for its customers. On occasion, Ameren Missouri's and Ameren Illinois' prior-period transactions will be resettled outside the routine settlement process because of a change in MISO’s tariff or a material interpretation thereof. In these cases, Ameren Missouri and Ameren Illinois recognize expenses associated with resettlements once the resettlement is probable and the resettlement amount can be estimated and recognize revenues once the resettlement amount is received.
Stock-Based Compensation 
Stock-based Compensation
Stock-based compensation cost is measured at the grant date based on the fair value of the award, net of an assumed forfeiture rate. Ameren recognizes as compensation expense the estimated fair value of stock-based compensation on a straight-line basis over the requisite service period.
Excise Taxes 
Excise Taxes
Ameren Missouri and Ameren Illinois collect from their customers certain excise taxes that are levied on the sale or distribution of natural gas and electricity. Excise taxes are levied on Ameren Missouri's electric and natural gas businesses and on Ameren Illinois' natural gas business. They are recorded gross in “Operating Revenues – Electric,” “Operating Revenues – Gas,” and “Operating Expenses – Taxes other than income taxes” on the statement of income or the statement of income and comprehensive income. Excise taxes for electric service in Illinois are levied on customers and are therefore not included in Ameren Illinois' revenues and expenses.
Unamortized Debt Discount, Premium, And Expense 
Unamortized Debt Discounts, Premiums, and Issuance Costs
Long-term debt discounts, premiums, and issuance costs are amortized over the lives of the related issuances. Credit facility fees are amortized over the credit facility term.
Income Taxes 
Income Taxes
Ameren uses an asset and liability approach for its financial accounting and reporting of income taxes, in accordance with authoritative accounting guidance. Deferred tax assets and liabilities are recognized for transactions that are treated differently for financial reporting and income tax return purposes. These deferred tax assets and liabilities are based on statutory tax rates.
We recognize that regulators will probably reduce future revenues for deferred tax liabilities that were initially recorded at rates in excess of the current statutory rate. Therefore, reductions in deferred tax liabilities that were recorded because of decreases in the statutory rate have been credited to a regulatory liability. A regulatory asset has been established to recognize the probable recovery through future customer rates of tax benefits related to the equity component of allowance for funds used during construction, as well as the effects of tax rate changes.
Investment tax credits used on tax returns for prior years have been deferred as a noncurrent liability. The credits are being amortized over the useful lives of the related investment. Deferred income taxes were recorded on the temporary difference represented by the deferred investment tax credits and a corresponding regulatory liability. This recognizes the expected reduction in rates for future lower income taxes associated with the amortization of the investment tax credits. See Note 13 – Income Taxes.
Ameren Missouri, Ameren Illinois, and all the other Ameren subsidiary companies are parties to a tax allocation agreement with Ameren (parent) that provides for the allocation of consolidated tax liabilities. The tax allocation agreement specifies that each party be allocated an amount of tax similar to that which would be owed or refunded had the party been separately subject to tax. Any net benefit attributable to the parent is reallocated to the other parties. This reallocation is treated as a capital contribution to the party receiving the benefit.
Earnings Per Share 
Earnings per Share
Basic earnings per share is computed by dividing net income attributable to Ameren common shareholders by the weighted-average number of common shares outstanding during the period. Earnings per diluted share is computed by dividing net income attributable to Ameren common shareholders by the weighted-average number of diluted common shares outstanding during the period. Earnings per diluted share reflects the potential dilution that would occur if certain stock-based performance share units were settled. The number of performance share units assumed to be settled was 1.0 million, 1.8 million, and 1.9 million for the years ended December 31, 2015, 2014, and 2013, respectively. There were no potentially dilutive securities excluded from the diluted earnings per share calculations for the years ended December 31, 2015, 2014, and 2013.
Accounting Changes and Other Matters 
Accounting Changes and Other Matters
The following is a summary of recently adopted authoritative accounting guidance, as well as guidance issued but not yet adopted, that could affect the Ameren Companies.
Revenue from Contracts with Customers
In May 2014, the FASB issued authoritative accounting guidance that changes the criteria for recognizing revenue from a contract with a customer. The underlying principle of the guidance is that an entity will recognize revenue for the transfer of promised goods or services to customers at an amount that the entity expects to be entitled to in exchange for those goods or services. The guidance also requires additional disclosures to enable users of financial statements to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. Entities can apply the guidance retrospectively to each reporting period presented or retrospectively by recording a cumulative effect adjustment to retained earnings in the period of initial adoption. The Ameren Companies are currently assessing the impacts of this guidance on their results of operations, financial position, and disclosures, including their accounting for contributions in aid of construction and similar arrangements, as well as the transition method that they will use to adopt the guidance. In August 2015, the FASB deferred the effective date of this revenue guidance to the first quarter of 2018, with an option for entities to early adopt in the first quarter of 2017. The Ameren Companies do not expect to early adopt this guidance.
Amendments to the Consolidation Analysis
In February 2015, the FASB issued authoritative accounting guidance that amends the consolidation analysis for variable interest entities and voting interest entities. The new guidance affects (1) limited partnerships and similar legal entities, (2) evaluating fees paid to a decision maker or service provider as a variable interest, (3) the effect of fee arrangements on the primary beneficiary determination, (4) the effect of related parties on the primary beneficiary determination, and (5) certain investment funds. The guidance is effective for the Ameren Companies in the first quarter of 2016, and can be applied retrospectively to each reporting period presented or retrospectively by recording a cumulative effect adjustment to retained earnings in the period of initial adoption. The Ameren Companies are currently assessing this guidance and do not expect any material impacts to their results of operations, financial position or cash flows.
Presentation of Debt Issuance Costs
In April 2015, the FASB issued authoritative accounting guidance to simplify the presentation of debt issuance costs in the balance sheet. The guidance requires debt issuance costs to be presented as a reduction to the associated debt liability. Previously, debt issuance costs were presented in "Other assets" on the Ameren Companies' balance sheets. The Ameren Companies early adopted this standard in 2015 and applied the guidance retrospectively. At December 31, 2015, debt issuance costs of $43 million, $19 million, and $18 million were presented in "Long-term debt, net" on Ameren's, Ameren Missouri's, and Ameren Illinois' balance sheets, respectively. At December 31, 2014, debt issuance costs of $35 million, $18 million, and $17 million previously presented in "Other assets" on Ameren's, Ameren Missouri's, and Ameren Illinois' respective balance sheets were reclassified to Long-term debt, net" for comparative purposes. See Note 5 – Long-Term Debt and Equity Financings for additional information. The implementation of this authoritative accounting guidance did not affect the Ameren Companies' results of operations or cash flows.
Balance Sheet Classification of Deferred Income Taxes
In November 2015, the FASB issued authoritative accounting guidance to simplify the presentation of deferred income taxes in the balance sheet. The guidance requires all deferred tax assets and liabilities, along with any related valuation allowances, to be classified as noncurrent on the balance sheet. Previously, the current portion of deferred taxes was presented as "Current accumulated deferred income taxes, net" and the noncurrent portion of deferred taxes was presented as "Accumulated deferred income taxes, net" on the Ameren Companies' balance sheets. The Ameren Companies early adopted this standard in 2015 and applied the guidance retrospectively. At December 31, 2014, the current deferred income taxes of $352 million, $49 million, and $160 million, which were previously presented as "Current accumulated deferred income taxes, net" on Ameren's, Ameren Missouri's, and Ameren Illinois' respective balance sheets, were reclassified and presented in "Accumulated deferred income taxes, net" for comparative purposes. The implementation of this authoritative accounting guidance did not affect the Ameren Companies' results of operations or cash flows.
Leases
In February 2016, the FASB issued authoritative accounting guidance that will require an entity to recognize assets and liabilities arising from a lease. Consistent with current GAAP, the recognition, measurement, and presentation of expenses and cash flows arising from a lease will depend primarily on its classification as a finance or operating lease. The guidance also requires additional disclosures to enable users of financial statements to understand the amount, timing, and uncertainty of cash flows arising from leases. The guidance will be effective for the Ameren Companies in the first quarter of 2019, and includes an option for entities to early adopt. The guidance requires a retrospective cumulative adjustment to retained earnings in the period of initial adoption. The Ameren Companies are currently assessing the impacts of this guidance on their results of operations, financial position, cash flows and disclosures.
Summary Of Significant Accounting Policies (Tables)
Schedule Of Materials And Supplies 
The following table presents a breakdown of materials and supplies for each of the Ameren Companies at December 31, 2015 and 2014:
 
 
Ameren Missouri
 
Ameren Illinois
 
Ameren
2015
 
 
 
 
 
 
Fuel(a)
 
$
173

 
$
—

 
$
173

Gas stored underground
 
10

 
87

 
97

Other materials and supplies
 
204

 
64

 
268

Total materials and supplies
 
$
387

 
$
151

 
$
538

2014
 
 
 
 
 
 
Fuel(a)
 
$
134

 
$
—

 
$
134

Gas stored underground
 
16

 
111

 
127

Other materials and supplies
 
197

 
66

 
263

Total materials and supplies
 
$
347

 
$
177

 
$
524

(a)
Consists of coal, oil, and propane.
Schedule Of Rates Used For Allowance For Funds Used During Construction 
The following table presents the annual allowance for funds used during construction rates that were applied to construction projects in 2015, 2014, and 2013:
 
2015
 
2014
 
2013
Ameren Missouri
7
%
 
7
%
 
8
%
Ameren Illinois
6
%
 
2
%
 
8
%
Schedule Of Asset Retirement Obligations 
The following table provides a reconciliation of the beginning and ending carrying amount of AROs for the years ended December 31, 2015 and 2014:
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
 
Balance at December 31, 2013
$
366

 
$
3

 
$
369

 
Liabilities incurred
2

 
—

 
2

 
Liabilities settled
(2
)
 
(a)

 
(2
)
 
Accretion in 2014(b)
21

 
(a)

 
21

 
Change in estimates(c)
2

 
4

 
6

 
Balance at December 31, 2014
$
389

 
$
7

(d) 
$
396

 
Liabilities incurred
3

 
—

 
3

 
Liabilities settled
(1
)
 
(1
)
 
(2
)
 
Accretion in 2015(b)
23

 
(a)

 
23

 
Change in estimates(e)
203

 
(a)

 
203

 
Balance at December 31, 2015
$
617

(f) 
$
6

(d) 
$
623

(f) 

(a)
Less than $1 million.
(b)
Accretion expense was recorded as an increase to regulatory assets at Ameren Missouri and Ameren Illinois.
(c)
The ARO increase resulted in a corresponding increase recorded to "Property and Plant, Net." Ameren Illinois changed its fair value estimate for asbestos removal.
(d)
Included in “Other deferred credits and liabilities” on the balance sheet.
(e)
The ARO increase resulted in a corresponding increase recorded to "Property and Plant, Net." Ameren and Ameren Missouri increased their AROs related to the decommissioning of the Callaway energy center by $99 million to reflect the 2015 cost study and funding analysis filed with the MoPSC, the extension of the estimated operating life until 2044, and a reduction in the discount rate assumption. See Note 10 – Callaway Energy Center for additional information. In addition, as a result of new federal regulations, Ameren and Ameren Missouri recorded an increase of $100 million to their AROs associated with CCR storage facilities. See Note 15 – Commitments and Contingencies for additional information. Ameren and Ameren Missouri also increased their AROs by $4 million due to a change in the estimated retirement dates of the Meramec and Rush Island energy centers as a result of the MoPSC's April 2015 electric rate order.
(f)
Balance included $5 million in "Other current liabilities" on the balance sheet as of December 31, 2015
Schedule Of Excise Taxes 
The following table presents the excise taxes recorded in “Operating Revenues – Electric,” “Operating Revenues – Gas,” and “Operating Expenses – Taxes other than income taxes” for the years ended December 31, 2015, 2014, and 2013:
 
2015
 
2014
 
2013
Ameren Missouri
$
156

 
$
151

 
$
152

Ameren Illinois
57

 
64

 
61

Ameren
$
213

 
$
215

 
$
213

Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] 
Supplemental Cash Flow Information
The following table presents additional information regarding Ameren's consolidated statement of cash flows for the years ended December 31, 2015, 2014, and 2013:
 
2015
 
2014
 
2013
Cash paid (refunded) during the year:
Interest
 
 
 
 
 
Continuing operations(a)
$
335

 
$
333

 
$
362

Discontinued operations(b)
—

 
—

 
31

 
$
335

 
$
333

 
$
393

 
 
 
 
 
 
Income taxes, net
 
 
 
 
 
Continuing Operations
$
(17
)
 
$
(41
)
 
$
116

Discontinued Operations
2

 
14

 
(108
)
 
$
(15
)
 
$
(27
)
 
$
8

(a)
Net of $17 million, $18 million, and $20 million capitalized, respectively.
(b)
Net of $- million, $- million, and $17 million capitalized, respectively.
Rate And Regulatory Matters (Tables)
Schedule Of Regulatory Assets And Liabilities
The following table presents our regulatory assets and regulatory liabilities at December 31, 2015 and 2014:
 
 
2015
 
2014
 
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
 
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
Current regulatory assets:
 
 
 
 
 
 
 
 
 
 
 
 
 
Under-recovered FAC(a)(b)
 
$
37

 
$
—

 
$
37

 
 
$
128

 
$
—

 
$
128

Under-recovered Illinois electric power costs(c)
 
—

 
3

 
3

 
 
—

 
2

 
2

Under-recovered PGA(c)
 
—

 
8

 
8

 
 
—

 
20

 
20

MTM derivative losses(d)
 
29


45

 
74

 
 
32

 
42

 
74

Energy efficiency riders(e)

 
23

 
—

 
23

 
 
3

 
—

 
3

IEIMA revenue requirement reconciliation adjustment(a)(f)
 
—

 
103

 
103

 
 
—

 
65

 
65

FERC revenue requirement reconciliation adjustment(a)(g)

 
—

 
8

 
12

 
 
—

 
—

 
3

Total current regulatory assets
 
$
89

 
$
167

 
$
260

 
 
$
163

 
$
129

 
$
295

Noncurrent regulatory assets:
 
 
 
 
 
 
 
 
 
 
 
 
 
Pension and postretirement benefit costs(h)
 
$
95

 
$
202

 
$
297

 
 
$
148

 
$
275

 
$
423

Income taxes(i)
 
254

 
4

 
258

 
 
253

 
3

 
256

Asset retirement obligations(j)
 
—

 
4

 
4

 
 
—

 
5

 
5

Callaway costs(a)(k)
 
32

 
—

 
32

 
 
36

 
—

 
36

Unamortized loss on reacquired debt(a)(l)
 
69

 
69

 
138

 
 
72

 
80

 
152

Contaminated facilities costs(m)
 
—

 
230

 
230

 
 
—

 
251

 
251

MTM derivative losses(d)
 
15


175

 
190



14

 
144

 
158

Storm costs(a)(n)
 
—

 
9

 
9

 
 
—

 
3

 
3

Demand-side costs before the MEEIA implementation(a)(o)
 
31

 
—

 
31

 
 
44

 
—

 
44

Workers’ compensation claims(p)
 
6

 
7

 
13

 
 
7

 
7

 
14

Credit facilities fees(q)
 
4

 
—

 
4

 
 
5

 
—

 
5

Construction accounting for pollution control equipment(a)(r)
 
20

 
—

 
20

 
 
21

 
—

 
21

Solar rebate program(a)(s)
 
74

 
—

 
74

 
 
88

 
—

 
88

IEIMA revenue requirement reconciliation adjustment(a)(f)
 
—

 
62

 
62

 
 
—

 
101

 
101

FERC revenue requirement reconciliation adjustment(a)(g)
 
—

 
5

 
11

 
 
—

 
8

 
12

Other
 
5

 
4

 
9

 
 
7

 
6

 
13

Total noncurrent regulatory assets
 
$
605

 
$
771

 
$
1,382

 
 
$
695

 
$
883

 
$
1,582

Current regulatory liabilities:
 
 
 
 
 
 
 
 
 
 
 
 
 
Over-recovered FAC(b)
 
$
9

 
$
—

 
$
9

 
 
$
—

 
$
—

 
$
—

Over-recovered Illinois electric power costs(c)
 
—

 
6

 
6

 
 
—

 
26

 
26

Over-recovered PGA(c)
 
3

 
—

 
3

 
 
2

 
25

 
27

MTM derivative gains(d)
 
16

 
1

 
17


 
16

 
1

 
17

FERC revenue requirement reconciliation adjustment(g)
 
—

 
—

 
—

 
 
—

 
11

 
11

Estimated refund for FERC complaint cases, orders, and audit findings(t)
 
—

 
32

 
45

 
 
—

 
21

 
25

Total current regulatory liabilities
 
$
28

 
$
39

 
$
80

 
 
$
18

 
$
84

 
$
106

Noncurrent regulatory liabilities:
 
 
 
 
 
 
 
 
 
 
 
 
 
Income taxes(u)
 
$
36

 
$
6

 
$
42

 
 
$
41

 
$
14

 
$
55

Uncertain tax positions tracker(v)
 
6

 
—

 
6

 
 
7

 
—

 
7

Removal costs(w)
 
933

 
671

 
1,605

 
 
886

 
643

 
1,529

Asset retirement obligation(j)
 
167

 
—

 
167

 
 
182

 
—

 
182

Bad debt riders(x)
 
—

 
6

 
6

 
 
—

 
7

 
7

Pension and postretirement benefit costs tracker(y)
 
19

 
—

 
19

 
 
24

 
—

 
24

Energy efficiency riders(e)
 
—

 
36

 
36

 
 
—

 
39

 
39

Renewable energy credits(z)
 
—

 
12

 
12

 
 
1

 
—

 
1

Storm tracker(aa)
 
9

 
—

 
9

 
 
6

 
—

 
6

Other
 
2

 
1

 
3

 
 
—

 
—

 
—

Total noncurrent regulatory liabilities
 
$
1,172

 
$
732

 
$
1,905

 
 
$
1,147

 
$
703

 
$
1,850

(a)
These assets earn a return.
(b)
Under-recovered or over-recovered fuel costs to be recovered or refunded through the FAC. Specific accumulation periods aggregate the under-recovered or over-recovered costs over four months, any related adjustments that occur over the following four months, and the recovery from or refund to customers that occurs over the next eight months.
(c)
Under-recovered or over-recovered costs from utility customers. Amounts will be recovered from, or refunded to, customers within one year of the deferral.
(d)
Deferral of commodity-related derivative MTM losses or gains. See Note 7 – Derivative Financial Instruments for additional information.
(e)
The Ameren Missouri balance relates to the MEEIA. Beginning in January 2014, the MEEIA rider allowed Ameren Missouri to collect from or refund to customers any annual difference in the actual amounts incurred and the amounts collected from customers for the MEEIA program costs and its net shared benefits. Under the MEEIA rider, collections from or refunds to customers occur one year after the program costs and lost revenues are incurred. The Ameren Illinois balance relates to a regulatory tracking mechanism to recover its electric and natural gas costs associated with developing, implementing, and evaluating customer energy efficiency and demand response programs. Any under-recovery or over-recovery will be collected from or refunded to customers over the 12 months following the plan year.
(f)
The difference between Ameren Illinois' annual revenue requirement calculated under the IEIMA's performance-based formula ratemaking framework and the revenue requirement included in customer rates for that year. Subject to ICC approval, these amounts will be collected from or refunded to customers with interest within two years.
(g)
Ameren Illinois' and ATXI's annual revenue requirement reconciliation adjustments calculated pursuant to the FERC's electric transmission formula ratemaking framework. The under-recovery or over-recovery will be recovered from or refunded to customers within two years.
(h)
These costs are being amortized in proportion to the recognition of prior service costs (credits) and actuarial losses (gains) attributable to Ameren’s pension plan and postretirement benefit plans. See Note 11 – Retirement Benefits for additional information.
(i)
Tax benefits related to the equity component of allowance for funds used during construction, as well as the effects of tax rate changes. This will be recovered over the expected life of the related assets.
(j)
Recoverable or refundable removal costs for AROs, including net realized and unrealized gains and losses related to the nuclear decommissioning trust fund investments. See Note 1 – Summary of Significant Accounting Policies – Asset Retirement Obligations and Investments.
(k)
Ameren Missouri’s Callaway energy center operations and maintenance expenses, property taxes, and carrying costs incurred between the plant in-service date and the date the plant was reflected in rates. These costs are being amortized over the remaining life of the energy center's original operating license through 2024.
(l)
Losses related to reacquired debt. These amounts are being amortized over the lives of the related new debt issuances or the original lives of the old debt issuances if no new debt was issued.
(m)
The recoverable portion of accrued environmental site liabilities that will be collected from electric and natural gas customers through ICC-approved cost recovery riders. The period of recovery will depend on the timing of remediation expenditures. See Note 15 – Commitments and Contingencies for additional information.
(n)
Storm costs from 2013 and 2015 deferred in accordance with the IEIMA. These costs are being amortized over five-year periods beginning in 2013 and 2015, respectively.
(o)
Demand-side costs incurred prior to implementation of the MEEIA in 2013, including the costs of developing, implementing, and evaluating customer energy efficiency and demand response programs. Costs incurred from May 2008 through September 2008 are being amortized over a 10-year period that began in March 2009. Costs incurred from October 2008 through December 2009 are being amortized until May 2017. Costs incurred from January 2010 through February 2011 are being amortized over a six-year period that began in August 2011. Costs incurred from March 2011 through July 2012 are being amortized over a six-year period that began in January 2013. Costs incurred from August 2012 through December 2012 are being amortized over a six-year period that began in June 2015.
(p)
The period of recovery will depend on the timing of actual expenditures.
(q)
Ameren Missouri’s costs incurred to enter into and maintain the Missouri Credit Agreement. Additional costs were incurred in December 2014 to amend and restate the Missouri Credit Agreement. These costs are being amortized over the life of the credit facility, ending in December 2019, to construction work in progress, which will be depreciated when assets are placed into service.
(r)
The MoPSC’s May 2010 electric rate order allowed Ameren Missouri to record an allowance for funds used during construction for pollution control equipment at its Sioux energy center until the cost of that equipment was included in customer rates beginning in 2011. These costs are being amortized over the expected life of the Sioux energy center, which is currently through 2033.
(s)
Costs associated with Ameren Missouri's solar rebate program beginning in August 2012 to fulfill its renewable energy portfolio requirement. These costs are being amortized over three years, beginning in June 2015.
(t)
Estimated refunds to transmission customers related to FERC orders. See Ameren Illinois Electric Transmission Rate Refund and FERC Complaint Cases above.
(u)
Unamortized portion of investment tax credits and reductions to deferred tax liabilities recorded at rates in excess of current statutory rates. The unamortized portion of investment tax credits and the reduction to deferred tax liabilities are being amortized over the expected life of the underlying assets.
(v)
The tracker is amortized over three years, beginning from the date the amounts are included in rates. See Note 13 – Income Taxes for additional information.
(w)
Estimated funds collected for the eventual dismantling and removal of plant from service, net of salvage value, upon retirement related to our rate-regulated operations.
(x)
A regulatory tracking mechanism for the difference between the level of bad debt incurred by Ameren Illinois under GAAP and the level of such costs included in electric and natural gas rates. The over-recovery relating to 2013 was refunded to customers from June 2014 through May 2015. The over-recovery relating to 2014 will be refunded to customers from June 2015 through May 2016. The over-recovery relating to 2015 will be refunded to customers from June 2016 through May 2017.
(y)
A regulatory tracking mechanism for the difference between the level of pension and postretirement benefit costs incurred by Ameren Missouri under GAAP and the level of such costs included in rates. For periods prior to December 2014, the MoPSC's April 2015 electric rate order directed the amortization to occur over three to five years, beginning in June 2015. For periods after December 2014, the amortization period will be determined in a future electric rate case.
(z)
The Ameren Missouri balance includes the costs of renewable energy credits to fulfill Ameren Missouri's renewable energy portfolio requirement from August 2012 through December 2013, which were less than the amount included in rates. These costs are being amortized over three years beginning in June 2015. The Ameren Illinois balance includes funds collected from customers for the purchase of renewable energy credits through IPA procurements for distributed generation. The balance will be amortized as renewable energy credits are purchased.
(aa)
A regulatory tracking mechanism at Ameren Missouri for the difference between the level of storm costs incurred in a particular year and the level of such costs included in rates. For periods prior to December 2014, the MoPSC's April 2015 electric rate order directed the amortization to occur over five years, beginning in June 2015. For periods after December 2014, the amortization period will be determined in a future electric rate case. The April 2015 MoPSC order did not approve the continued use of the regulatory tracking mechanisms for storm costs.
Property And Plant, Net (Tables)
Schedule Of Property And Plant, Net 
The following table presents property and plant, net, for each of the Ameren Companies at December 31, 2015 and 2014:
 
 
Ameren
Missouri(a)
 
Ameren
Illinois
 
Other
 
Ameren(a)
2015
 
 
 
 
 
 
 
 
Property and plant, at original cost:
 
 
 
 
 
 
 
 
Electric
 
$
17,521

 
$
7,253

 
$
387

 
$
25,161

Natural gas
 
445

 
1,997

 
—

 
2,442

 
 
17,966

 
9,250

 
387

 
27,603

Less: Accumulated depreciation and amortization
 
7,460

 
2,632

 
255

 
10,347

 
 
10,506

 
6,618

 
132

 
17,256

Construction work in progress:
 
 
 
 
 
 
 
 
Nuclear fuel in process
 
275

 
—

 
—

 
275

Other
 
402

 
230

 
636

 
1,268

Property and plant, net
 
$
11,183

 
$
6,848

 
$
768

 
$
18,799

2014
 
 
 
 
 
 
 
 
Property and plant, at original cost:
 
 
 
 
 
 
 
 
Electric
 
$
17,052

 
$
6,517

 
$
344

 
$
23,913

Natural gas
 
431

 
1,854

 
—

 
2,285

 
 
17,483

 
8,371

 
344

 
26,198

Less: Accumulated depreciation and amortization
 
7,086

 
2,422

 
251

 
9,759

 
 
10,397

 
5,949

 
93

 
16,439

Construction work in progress:
 
 
 
 
 
 
 
 
Nuclear fuel in process
 
209

 
—

 
—

 
209

Other
 
261

 
216

 
299

 
776

Property and plant, net
 
$
10,867

 
$
6,165

 
$
392

 
$
17,424


(a)
Amounts in Ameren and Ameren Missouri include two CTs under separate capital lease agreements. The gross cumulative asset value of those agreements was $233 million at December 31, 2015 and 2014. The total accumulated depreciation associated with the two CTs was $72 million and $66 million at December 31, 2015 and 2014, respectively. In addition, Ameren Missouri has investments in debt securities, which were classified as held-to-maturity and recorded in "Other assets", related to the two CTs from the city of Bowling Green and Audrain County. As of December 31, 2015 and 2014, the carrying value of these debt securities was $288 million and $294 million, respectively.
Accrued Capital Expenditures 
The following table provides accrued capital and nuclear fuel expenditures at December 31, 2015, 2014, and 2013, which represent noncash investing activity excluded from the accompanying statements of cash flows:
 
Ameren(a)
 
Ameren
Missouri
 
Ameren
Illinois
Accrued capital expenditures:
 
 
 
 
 
2015
$
235

 
$
85

 
$
92

2014
181

 
72

 
59

2013
175

 
74

 
86

Accrued nuclear fuel expenditures:
 
 
 
 
 
2015
16

 
16

 
(b)

2014
13

 
13

 
(b)

2013
8

 
8

 
(b)


(a)
Includes amounts for Ameren registrant and nonregistrant subsidiaries.
(b)
Not applicable.
Short-Term Debt And Liquidity (Tables)
Schedule Of Maximum Aggregate Amount Available On Credit Agreements 
The following table presents the maximum aggregate amount available to each borrower under each facility which will expire in December 2019 (the amount being each borrower's "Borrowing Sublimit"):
 
 
Missouri Credit Agreement
Illinois
Credit Agreement
Ameren
 
$
700

$
500

Ameren Missouri
 
800

(a)

Ameren Illinois
 
  (a)

800

(a)
Not applicable.
Schedule of Commercial Paper 
The following table summarizes the borrowing activity and relevant interest rates under Ameren (parent)'s, Ameren Missouri's and Ameren Illinois' commercial paper programs, for the years ended December 31, 2015 and 2014:
 
 
Ameren (parent)
Ameren Missouri
Ameren Illinois
Ameren Consolidated
2015
 
 
 
 
 
 
Average daily commercial paper outstanding
 
$
721

 
$
42

$
4

$
767

Outstanding borrowings at period-end
 
301

 
—

—

301

Weighted-average interest rate
 
0.57
%
 
0.50
%
0.44
%
0.55
%
Peak commercial paper during period(a)
 
$
874

 
$
294

$
48

$
1,108

Peak interest rate
 
0.91
%
 
0.60
%
0.60
%
0.91
%
2014
 
 
 
 
 
 
Average daily commercial paper outstanding
 
$
423

 
$
110

$
165

$
639

Outstanding borrowings at period-end
 
585

 
97

32

714

Weighted-average interest rate
 
0.36
%
 
0.38
%
0.32
%
0.36
%
Peak commercial paper during period(a)
 
$
625

 
$
495

$
300

$
910

Peak interest rate
 
0.75
%
 
0.70
%
0.60
%
0.75
%
(a)
The timing of peak commercial paper issuances varies by company, and therefore the peak amounts presented by company might not equal the Ameren Consolidated peak commercial paper issuances for the period.
Long-Term Debt And Equity Financings (Tables)
Schedule of Long-term Debt Instruments 
The following table presents long-term debt outstanding, including maturities due within one year, for the Ameren Companies as of December 31, 2015 and 2014:
 
2015
 
2014
Ameren (Parent):
 
 
 
2.70% Senior unsecured notes due 2020
$
350

 
$
—

3.65% Senior unsecured notes due 2026
350

 
—

Total long-term debt, gross
700

 
—

Less: Unamortized debt issuance costs(a)
(6
)
 
—

Long-term debt, net
$
694

 
$
—

Ameren Missouri:
 
 
 
Senior secured notes:(b)
 
 
 
4.75% Senior secured notes due 2015
—

 
114

5.40% Senior secured notes due 2016
260

 
260

6.40% Senior secured notes due 2017
425

 
425

6.00% Senior secured notes due 2018(c)
179

 
179

5.10% Senior secured notes due 2018
199

 
199

6.70% Senior secured notes due 2019(c)
329

 
329

5.10% Senior secured notes due 2019
244

 
244

5.00% Senior secured notes due 2020
85

 
85

3.50% Senior secured notes due 2024
350

 
350

5.50% Senior secured notes due 2034
184

 
184

5.30% Senior secured notes due 2037
300

 
300

8.45% Senior secured notes due 2039(c)
350

 
350

3.90% Senior secured notes due 2042(c)
485

 
485

3.65% Senior secured notes due 2045
250

 
—

Environmental improvement and pollution control revenue bonds:
 
 
 
1992 Series due 2022(d)(e)
47

 
47

1993 5.45% Series due 2028(f)
(f)

 
(f)

1998 Series A due 2033(d)(e)
60

 
60

1998 Series B due 2033(d)(e)
50

 
50

1998 Series C due 2033(d)(e)
50

 
50

Capital lease obligations:
 
 
 
City of Bowling Green capital lease (Peno Creek CT) due 2022
48

 
54

Audrain County capital lease (Audrain County CT) due 2023
240

 
240

Total long-term debt, gross
4,135

 
4,005

Less: Unamortized discount and premium
(6
)
 
(6
)
Less: Unamortized debt issuance costs(a)
(19
)
 
(18
)
Less: Maturities due within one year
(266
)
 
(120
)
Long-term debt, net
$
3,844

 
$
3,861

 
2015
 
2014
Ameren Illinois:
 
 
 
Senior secured notes:
 
 
 
6.20% Senior secured notes due 2016(g)
$
54

 
$
54

6.25% Senior secured notes due 2016(h)
75

 
75

6.125% Senior secured notes due 2017(h)(i)
250

 
250

6.25% Senior secured notes due 2018(h)(i)
144

 
144

9.75% Senior secured notes due 2018(h)(i)
313

 
313

2.70% Senior secured notes due 2022(h)(i)
400

 
400

3.25% Senior secured notes due 2025(h)
300

 
300

6.125% Senior secured notes due 2028(h)
60

 
60

6.70% Senior secured notes due 2036(h)
61

 
61

6.70% Senior secured notes due 2036(g)
42

 
42

4.80% Senior secured notes due 2043(h)
280

 
280

4.30% Senior secured notes due 2044(h)
250

 
250

4.15% Senior secured notes due 2046(h)
250

 
—

Environmental improvement and pollution control revenue bonds:
 
 
 
5.90% Series 1993 due 2023(j)
(j)

 
(j)

5.70% 1994A Series due 2024(k)
(k)

 
(k)

1993 Series B-1 due 2028(e)(l)
17

 
17

Total long-term debt, gross
2,496

 
2,246

Less: Unamortized discount and premium
(7
)
 
(5
)
Less: Unamortized debt issuance costs(a)
(18
)
 
(17
)
Less: Maturities due within one year
(129
)
 
—

Long-term debt, net
$
2,342

 
$
2,224

Ameren consolidated long-term debt, net
$
6,880

 
$
6,085

(a)
Reflects the adoption of the new authoritative accounting guidance for the presentation of debt issuance costs. See Note 1 – Summary of Significant Accounting Policies for additional information.
(b)
These notes are collaterally secured by first mortgage bonds issued by Ameren Missouri under the Ameren Missouri mortgage indenture. The notes have a fall-away lien provision and will remain secured only as long as any first mortgage bonds issued under the Ameren Missouri mortgage indenture remain outstanding. Redemption, purchase, or maturity of all first mortgage bonds, including first mortgage bonds currently outstanding and any that may be issued in the future, would result in a release of the first mortgage bonds currently securing these notes, at which time these notes would become unsecured obligations. Considering the Ameren Missouri senior secured notes currently outstanding, we do not expect the first mortgage bond lien protection associated with these notes to fall away until 2042.
(c)
Ameren Missouri has agreed that so long as any of the 3.90% senior secured notes due 2042 are outstanding, Ameren Missouri will not permit a release date to occur, and so long as any of the 6.70% senior secured notes due 2019, 6.00% senior secured notes due 2018 and 8.45% senior secured notes due 2039 are outstanding, Ameren Missouri will not optionally redeem, purchase, or otherwise retire in full the outstanding first mortgage bonds not subject to release provisions.
(d)
These bonds are collaterally secured by first mortgage bonds issued by Ameren Missouri under the Ameren Missouri mortgage indenture and have a fall-away lien provision similar to that of Ameren Missouri's senior secured notes. The bonds are also backed by an insurance guarantee policy.
(e)
The interest rates, and the periods during which such rates apply, vary depending on our selection of defined rate modes. Maximum interest rates could reach 18% depending on the series of bonds. The bonds are callable at 100% of par value. The average interest rates for 2015 and 2014 were as follows:
    
 
2015
 
2014
Ameren Missouri 1992 Series due 2022
0.06%
 
0.10%
Ameren Missouri 1998 Series A due 2033
0.24%
 
0.26%
Ameren Missouri 1998 Series B due 2033
0.24%
 
0.27%
Ameren Missouri 1998 Series C due 2033
0.24%
 
0.26%
Ameren Illinois 1993 Series B-1 due 2028
0.49%
 
0.21%

(f)
These bonds are first mortgage bonds issued by Ameren Missouri under the Ameren Missouri mortgage bond indenture and are secured by substantially all Ameren Missouri property and franchises. The bonds are callable at 100% of par value. Less than $1 million principal amount of the bonds remain outstanding.
(g)
These notes are collaterally secured by first mortgage bonds issued by Ameren Illinois under the CILCO mortgage indenture. The notes have a fall-away lien provision, and Ameren Illinois could cause these notes to become unsecured at any time by redeeming the pollution control bonds 5.90% Series 1993 due 2023 (of which less than $1 million remains outstanding).
(h)
These notes are collaterally secured by mortgage bonds issued by Ameren Illinois under the Ameren Illinois mortgage indenture. They are secured by substantially all property of the former IP and CIPS. The notes have a fall-away lien provision and will remain secured only as long as any series of first mortgage bonds issued under the Ameren Illinois mortgage indenture remain outstanding. Redemption, purchase, or maturity of all mortgage bonds, including first mortgage bonds currently outstanding and any that may be issued in the future, would result in a release of the mortgage bonds currently securing these notes, at which time these notes would become unsecured obligations. Considering the Ameren Illinois senior secured notes currently outstanding, we do not expect the mortgage bond lien protection associated with these notes to fall away until 2024.
(i)
Ameren Illinois has agreed that so long as any of the 2.70% senior secured notes due 2022 are outstanding, Ameren Illinois will not permit a release date to occur, and so long as any of the 9.75% senior secured notes due 2018, 6.25% senior secured notes due 2018 and 6.125% senior secured notes due 2017 are outstanding, Ameren Illinois will not optionally redeem, purchase or otherwise retire in full the outstanding first mortgage bonds not subject to release provisions; therefore, a release date will not occur so long as any of these notes remain outstanding.
(j)
These bonds are first mortgage bonds issued by Ameren Illinois under the CILCO mortgage indenture. They are secured by substantially all property of the former CILCO. The bonds are callable at 100% of par value. Less than $1 million principal amount of the bonds remain outstanding.
(k)
These bonds are mortgage bonds issued by Ameren Illinois under the Ameren Illinois mortgage indenture. They are secured by substantially all property of the former IP and CIPS. The bonds are callable at 100% of par value. The bonds are also backed by an insurance guarantee policy. Less than $1 million principal amount of the bonds remains outstanding.
(l)
The bonds are callable at 100% of par value.
Schedule Of Maturities Of Long-Term Debt 
The following table presents the aggregate maturities of long-term debt, including current maturities, for the Ameren Companies at December 31, 2015:
 
Ameren
(parent)(a)
 
 Ameren
Missouri(a)
 
 Ameren
Illinois(a)
 
Ameren
Consolidated
2016
$
—

 
$
266

 
$
129

 
$
395

2017
—

 
431

 
250

 
681

2018
—

 
383

 
457

 
840

2019
—

 
581

 
—

 
581

2020
350

 
92

 
—

 
442

Thereafter
350

 
2,382

 
1,660

 
4,392

Total
$
700

 
$
4,135

 
$
2,496

 
$
7,331

(a)
Excludes unamortized discount and premium and debt issuance costs of $6 million, $25 million, and $25 million at Ameren (parent), Ameren Missouri, and Ameren Illinois, respectively.
Schedule Of Outstanding Preferred Stock 
The following table presents the outstanding preferred stock of Ameren Missouri and Ameren Illinois, which is redeemable, at the option of the issuer, at the prices shown below as of December 31, 2015 and 2014:
 
 
 
Redemption Price(per share)
 
2015
 
2014
Ameren Missouri:
 
 
 
 
 
 
 
Without par value and stated value of $100 per share, 25 million shares authorized
 
 
 
 
 
 
$3.50 Series
130,000 shares
 
$
110.00

 
$
13

 
$
13

$3.70 Series
40,000 shares
 
104.75

 
4

 
4

$4.00 Series
150,000 shares
 
105.625

 
15

 
15

$4.30 Series
40,000 shares
 
105.00

 
4

 
4

$4.50 Series
213,595 shares
 
110.00

(a) 
21

 
21

$4.56 Series
200,000 shares
 
102.47

 
20

 
20

$4.75 Series
20,000 shares
 
102.176

 
2

 
2

$5.50 Series A
14,000 shares
 
110.00

 
1

 
1

Total
 
 
 
$
80

 
$
80

Ameren Illinois:
 
 
 
 
 
 
 
With par value of $100 per share, 2 million shares authorized
 
 
 
 
 
 
4.00% Series
144,275 shares
 
$
101.00

 
$
14

 
$
14

4.08% Series
45,224 shares
 
103.00

 
5

 
5

4.20% Series
23,655 shares
 
104.00

 
2

 
2

4.25% Series
50,000 shares
 
102.00

 
5

 
5

4.26% Series
16,621 shares
 
103.00

 
2

 
2

4.42% Series
16,190 shares
 
103.00

 
2

 
2

4.70% Series
18,429 shares
 
103.00

 
2

 
2

4.90% Series
73,825 shares
 
102.00

 
7

 
7

4.92% Series
49,289 shares
 
103.50

 
5

 
5

5.16% Series
50,000 shares
 
102.00

 
5

 
5

6.625% Series
124,274 shares
 
100.00

 
12

 
12

7.75% Series
4,542 shares
 
100.00

 
1

 
1

Total
 
 
 
$
62

 
$
62

Total Ameren
 
 
 
$
142

 
$
142

(a)
In the event of voluntary liquidation, $105.50.
Schedule of Required and Actual Debt Ratios 
The following table summarizes the required and actual interest coverage ratios for interest charges, dividend coverage ratios, and bonds and preferred stock issuable as of December 31, 2015, at an assumed interest rate of 5% and dividend rate of 6%.
 
Required Interest
Coverage Ratio(a)
Actual Interest
Coverage Ratio
Bonds Issuable(b)
 
Required Dividend
Coverage Ratio(c)
Actual Dividend
Coverage Ratio
Preferred Stock
Issuable
 
Ameren Missouri
>2.0
3.8

$
3,385

  
>2.5
104.0

$
2,315

 
Ameren Illinois
>2.0
6.3

3,566

(d) 
>1.5
2.6

203

(e) 
(a)
Coverage required on the annual interest charges on first mortgage bonds outstanding and to be issued. Coverage is not required in certain cases when additional first mortgage bonds are issued on the basis of retired bonds.
(b)
Amount of bonds issuable based either on required coverage ratios or unfunded property additions, whichever is more restrictive. The amounts shown also include bonds issuable based on retired bond capacity of $946 million and $204 million at Ameren Missouri and Ameren Illinois, respectively.
(c)
Coverage required on the annual dividend on preferred stock outstanding and to be issued, as required in the respective company’s articles of incorporation.
(d)
Amount of bonds issuable by Ameren Illinois based on unfunded property additions and retired bonds solely under the former IP mortgage indenture. The amount of bonds issuable by Ameren Illinois is also subject to the lien restrictions contained in the Illinois Credit Agreement.
(e)
Preferred stock issuable is restricted by the amount of preferred stock that is currently authorized by Ameren Illinois' articles of incorporation.
Debt Redemption [Table Text Block] 
In January 2014, Ameren Illinois redeemed the following environmental improvement and pollution control revenue bonds at par value plus accrued interest:
Senior Secured Notes
Principal Amount
5.90% Series 1993 due 2023(a)
$
32

5.70% 1994A Series due 2024(a)
36

1993 Series C-1 5.95% due 2026
35

1993 Series C-2 5.70% due 2026
8

5.40% 1998A Series due 2028
19

5.40% 1998B Series due 2028
33

Total amount redeemed
$
163

(a)
Less than $1 million principal amount of the bonds remains outstanding after redemption.
Other Income And Expenses (Tables)
Other Income And Expenses
The following table presents the components of "Other Income and Expenses" in the Ameren Companies’ statements of income (loss) for the years ended December 31, 2015, 2014, and 2013:
 
2015
 
2014
 
2013
 
Ameren:(a)
 
 
 
 
 
 
Miscellaneous income:
 
 
 
 
 
 
Allowance for equity funds used during construction
$
30

 
$
34

 
$
37

 
Interest income on industrial development revenue bonds
27

 
27

 
27

 
Interest income (b)
14

  
10

  
3

 
Other
3

 
8

(c) 
2

 
Total miscellaneous income
$
74

 
$
79

 
$
69

 
Miscellaneous expense:
 
 
 
 
 
 
Donations
$
15

 
$
10

 
$
12

 
Other
15

 
12

 
14

 
Total miscellaneous expense
$
30

 
$
22

 
$
26

 
Ameren Missouri:
 
 
 
 
 
 
Miscellaneous income:
 
 
 
 
 
 
Allowance for equity funds used during construction
$
22

 
$
32

 
$
31

 
Interest income on industrial development revenue bonds
27

 
27

 
27

 
Interest income
1

 
1

 
—

 
Other
2

 
—

 
—

 
Total miscellaneous income
$
52

 
$
60

 
$
58

 
Miscellaneous expense:
 
 
 
 
 
 
Donations
$
5

 
$
6

 
$
4

 
Other
6

 
6

 
7

 
Total miscellaneous expense
$
11

 
$
12

 
$
11

 
Ameren Illinois:
 
 
 
 
 
 
Miscellaneous income:
 
 
 
 
 
 
Allowance for equity funds used during construction
$
8

 
$
2

 
$
6

 
Interest income (b)
12

  
7

  
2

 
Other
1

 
8

(c) 
2

 
Total miscellaneous income
$
21

 
$
17

 
$
10

 
Miscellaneous expense:
 
 
 
 
 
 
Donations
$
5

 
$
4

 
$
4

 
Other
7

 
4

 
5

 
Total miscellaneous expense
$
12

 
$
8

 
$
9

 
(a)
Includes amounts for Ameren registrant and nonregistrant subsidiaries and intercompany eliminations.
(b)
Includes Ameren Illinois' interest income on the IEIMA revenue requirement reconciliation adjustment regulatory assets.
(c)
Includes Ameren Illinois' income earned in 2014 from customer-requested construction.
Derivative Financial Instruments (Tables)
Open Gross Derivative Volumes By Commodity Type 
The following table presents open gross commodity contract volumes by commodity type for derivative assets and liabilities as of December 31, 2015 and 2014. As of December 31, 2015, these contracts ran through October 2018, March 2021, May 2032, and January 2019 for fuel oils, natural gas, power, and uranium, respectively.
  
Quantity (in millions, except as indicated)
 
2015
2014
Commodity
Ameren Missouri
Ameren Illinois
Ameren
Ameren Missouri
Ameren Illinois
Ameren
Fuel oils (in gallons)(a)
35
(b)
35
50
(b)
50
Natural gas (in mmbtu)
30
151
181
28
108
136
Power (in megawatthours)
1
10
11
1
11
12
Uranium (pounds in thousands)
494
(b)
494
332
(b)
332

(a)
Fuel oils consist of heating oil and ultra-low-sulfur diesel.
(b)
Not applicable.
Derivative Instruments Carrying Value 
The following table presents the carrying value and balance sheet location of all derivative commodity contracts, none of which were designated as hedging instruments, as of December 31, 2015 and 2014:
 
Balance Sheet Location
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
2015
 
 
 
 
 
 
 
Natural gas
Other current assets
$
—

$
1

$
1

 
Other assets
 
1

 
—

 
1

Power
Other current assets
 
16

 
—

 
16

 
Total assets (a)
$
17

$
1

$
18

Fuel oils
Other current liabilities
$
22

$
—

$
22

 
Other deferred credits and liabilities
 
7

 
—

 
7

Natural gas
MTM derivative liabilities
 
(b)

 
32

 
(b)

 
Other current liabilities
 
6

 
—

 
38

 
Other deferred credits and liabilities
 
8

 
18

 
26

Power
MTM derivative liabilities
 
(b)

 
13

 
(b)

 
Other current liabilities
 
—

 
—

 
13

 
Other deferred credits and liabilities
 
—

 
157

 
157

Uranium
Other current liabilities
 
1

 
—

 
1

 
Total liabilities (c)
$
44

$
220

$
264

2014
 
 
 
 
 
 
 
Fuel oils
Other current assets
$
2

$
—

$
2

Natural gas
Other current assets
 
1

 
1

 
2

Power
Other current assets
 
15

 
—

 
15

 
Total assets (a)
$
18

$
1

$
19

Fuel oils
Other current liabilities
$
22

$
—

$
22

 
Other deferred credits and liabilities
 
7

 
—

 
7

Natural gas
MTM derivative liabilities
 
(b)

 
31

 
(b)

 
Other current liabilities
 
6

 
—

 
37

 
Other deferred credits and liabilities
 
6

 
13

 
19

Power
MTM derivative liabilities
 
(b)

 
11

 
(b)

 
Other current liabilities
 
3

 
—

 
14

 
Other deferred credits and liabilities
 
—

 
131

 
131

Uranium
Other current liabilities
 
2

 
—

 
2

 
Total liabilities (c)
$
46

$
186

$
232

(a)
Because all contracts qualifying for hedge accounting receive regulatory deferral, the cumulative amount of pretax net gains on all derivative instruments is deferred as a regulatory liability.
(b)
Balance sheet line item not applicable to registrant.
(c)
Because all contracts qualifying for hedge accounting receive regulatory deferral, the cumulative amount of pretax net losses on all derivative instruments is deferred as a regulatory asset.
Derivative Instruments With Credit Risk-Related Contingent Features 
The following table presents, as of December 31, 2015, the aggregate fair value of all derivative instruments with credit risk-related contingent features in a gross liability position, the cash collateral posted, and the aggregate amount of additional collateral that counterparties could require. The additional collateral required is the net liability position allowed under the master netting arrangements or similar agreements assuming (1) the credit risk-related contingent features underlying these arrangements were triggered on December 31, 2015, and (2) those counterparties with rights to do so requested collateral.
 
Aggregate Fair Value of
Derivative Liabilities(a)
 
Cash
Collateral Posted
 
Potential Aggregate Amount of
Additional Collateral Required(b)
2015
 
 
 
 
 
Ameren Missouri
$
87

 
$
9

 
$
72

Ameren Illinois
78

 
3

 
71

Ameren
$
165

 
$
12

 
$
143

(a)
Before consideration of master netting arrangements or similar agreements and including NPNS and other accrual contract exposures.
(b)
As collateral requirements with certain counterparties are based on master netting arrangements or similar agreements, the aggregate amount of additional collateral required to be posted is determined after consideration of the effects of such arrangements.
Offsetting Derivative Assets and Liabilities [Table Text Block] 
The following table provides the recognized gross derivative balances and the net amounts of those derivatives subject to an enforceable master netting arrangement or similar agreement as of December 31, 2015 and 2014:
 
 
 
 
Gross Amounts Not Offset on the Balance Sheet
 
 
Commodity Contracts Eligible to be Offset
 
Gross Amounts Recognized on the Balance Sheet
 
Derivative Instruments
 
Cash Collateral Received/Posted(a)
 
Net
Amount
2015
 
 
 
 
 
 
 
 
Assets:
 
 
 
 
 
 
 
 
Ameren Missouri
$
17

$
1

$
—

$
16

Ameren Illinois
 
1

 
—

 
—

 
1

Ameren
$
18

$
1

$
—

$
17

Liabilities:
 
 
 
 
 
 
 
 
Ameren Missouri
$
44

$
1

$
8

$
35

Ameren Illinois
 
220

 
—

 
3

 
217

Ameren
$
264

$
1

$
11

$
252

2014
 
 
 
 
 
 
 
 
Assets:
 
 
 
 
 
 
 
 
Ameren Missouri
$
18

$
5

$
—

$
13

Ameren Illinois
 
1

 
—

 
—

 
1

Ameren
$
19

$
5

$
—

$
14

Liabilities:
 
 
 
 
 
 
 
 
Ameren Missouri
$
46

$
5

$
5

$
36

Ameren Illinois
 
186

 
—

 
—

 
186

Ameren
$
232

$
5

$
5

$
222

(a)
Cash collateral received reduces gross asset balances and is included in “Other current liabilities” and “Other deferred credits and liabilities” on the balance sheet. Cash collateral posted reduces gross liability balances and is included in “Other current assets” and “Other assets” on the balance sheet.
Fair Value Measurements (Tables)
Fair Value Inputs, Assets and Liabilities, Quantitative Information 
The following table describes the valuation techniques and unobservable inputs utilized by the Ameren Companies for the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the periods ended December 31, 2015 and 2014:
 
 
Fair Value
 
 
 
 
Weighted
 
 
Assets
Liabilities
 
Valuation Technique(s)
Unobservable Input
Range
Average
 
Level 3 Derivative asset and liability – commodity contracts(a):
 
 
 
2015
 
 
 
 
 
 
 
 
 
Natural Gas
$
1

$
(1
)
 
Option model
Volatilities(%)(b)
35 – 55
45
 



 

Nodal basis($/mmbtu)(c)
(0.30) – 0
(0.20)
 



 
Discounted cash flow
Nodal basis($/mmbtu)(b)
(0.10) – 0
(0.10)
 
 
Fair Value
 
 
 
 
Weighted
 
 
Assets
Liabilities
 
Valuation Technique(s)
Unobservable Input
Range
Average
 



 

Counterparty credit risk(%)(c)(d)
0.40 – 12
7
 



 

Ameren Missouri credit risk(%)(c)(d)
0.40
(e)
 
Power(f)
16

(170
)
 
Discounted cash flow
Average forward peak and off-peak pricing – forwards/swaps($/MWh)(g)
22 – 39
29
 
 
 
 
 
 
Estimated auction price for FTRs($/MW)(b)
(270) – 2,057
211
 
 
 
 
 
 
Nodal basis($/MWh)(g)
(10) – (1)
(3)
 
 
 
 
 
 
Counterparty credit risk(%)(c)(d)
0.86
(e)
 
 
 
 
 
 
Ameren Illinois credit risk(%)(c)(d)
0.40
(e)
 
 
 
 
 
Fundamental energy production model
Estimated future gas prices($/mmbtu)(b)
3 – 4
4
 
 
 
 
 
 
Escalation rate(%)(b)(h)
3
(e)
 
 
 
 
 
Contract price allocation
Estimated renewable energy credit costs($/credit)(b)
5 – 7
6
 
Uranium
—

(1
)
 
Option model
Volatilities(%)(b)
20
(e)
 
 
 
 
 
Discounted cash flow
Average forward uranium pricing($/pound)(b)
35 – 42
37
 
 
 
 
 
 
Ameren Missouri credit risk(%)(c)(d)
0.40
(e)
2014
 
 
 
 
 
 
 
 
 
Fuel oils
$
2

$
(8
)
 
Option model
Volatilities(%)(c)
3 – 39
32
 
 
 
 
 
Discounted cash flow
Ameren Missouri credit risk(%)(c)(d)
0.43
(e)
 
 
 
 
 
 
Escalation rate(%)(b)(i)
5
(e)
 
Natural Gas
1

(2
)
 
Option model
Volatilities(%)(c)
31 – 144
63
 
 
 
 
 
 
Nodal basis($/mmbtu)(b)
(0.40) – 0
(0.20)
 
 
 
 
 
Discounted cash flow
Nodal basis($/mmbtu)(b)
(0.40) – 0.10
(0.20)
 
 
 
 
 
 
Counterparty credit risk(%)(c)(d)
0.43 – 13
3
 
 
 
 
 
 
Ameren Missouri and Ameren Illinois credit risk(%)(c)(d)
0.43
(e)
 
Power(f)
11

(144
)
 
Discounted cash flow
Average forward peak and off-peak pricing – forwards/swaps($/MWh)(g)
27 – 50
32
 
 
 
 
 
 
Estimated auction price for FTRs($/MW)(b)
(1,833) – 2,743
171
 
 
 
 
 
 
Nodal basis($/MWh)(b)
(6) – 0
(2)
 
 
 
 
 
 
Counterparty credit risk(%)(c)(d)
0.26
(e)
 
 
 
 
 
 
Ameren Missouri and Ameren Illinois credit risk(%)(c)(d)
0.43
(e)
 
 
 
 
 
Fundamental energy production model
Estimated future gas prices($/mmbtu)(b)
4 – 5
4
 
 
 
 
 
 
Escalation rate(%)(b)(h)
0 – 1
1
 
 
 
 
 
Contract price allocation
Estimated renewable energy credit costs($/credit)(b)
5 – 7
6
 
Uranium
—

(2
)
 
Discounted cash flow
Average forward uranium pricing($/pound)(b)
35 – 40
36
(a)
The derivative asset and liability balances are presented net of counterparty credit considerations.
(b)
Generally, significant increases (decreases) in this input in isolation would result in a significantly higher (lower) fair value measurement.
(c)
Generally, significant increases (decreases) in this input in isolation would result in a significantly lower (higher) fair value measurement.
(d)
Counterparty credit risk is applied only to counterparties with derivative asset balances. Ameren Missouri and Ameren Illinois credit risk is applied only to counterparties with derivative liability balances.
(e)
Not applicable.
(f)
Power valuations use visible third-party pricing evaluated by month for peak and off-peak demand through 2019. Valuations beyond 2019 use fundamentally modeled pricing by month for peak and off-peak demand.
(g)
The balance at Ameren is comprised of Ameren Missouri and Ameren Illinois power contracts, which respond differently to unobservable input changes because of their opposing positions.
(h)
Escalation rate applies to power prices 2026 and beyond.
(i)
Escalation rate applies to fuel oil prices 2017 and beyond.
Schedule Of Fair Value Hierarchy Of Assets And Liabilities Measured At Fair Value On Recurring Basis 
The following table sets forth, by level within the fair value hierarchy, our assets and liabilities measured at fair value on a recurring basis as of December 31, 2015:
 
 
 
Quoted Prices in
Active Markets for
Identical Assets
or Liabilities
(Level 1)
 
Significant Other
Observable
Inputs
(Level 2)
 
Significant Other
Unobservable
Inputs
(Level 3)
 
Total
 
Assets:
 
 
 
 
 
 
 
 
 
 
Ameren
Derivative assets – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Natural gas
 
$
—

 
$
1

 
$
1

 
$
2

 
 
Power
 
—

 
—

 
16

 
16

 
 
Total derivative assets – commodity contracts
 
$
—

 
$
1

 
$
17

 
$
18

 
 
Nuclear decommissioning trust fund:
 
 
 
 
 
 
 
 
 
 
Cash and cash equivalents
 
$
4

 
$
—

 
$
—

 
$
4

 
 
Equity securities:
 
 
 
 
 
 
 
 
 
 
U.S. large capitalization
 
364

 
—

 
—

 
364

 
 
Debt securities:
 
 
 
 
 
 
 
 
 
 
U.S. Treasury and agency securities
 
—

 
109

 
—

 
109

 
 
Corporate bonds
 
—

 
58

 
—

 
58

 
 
Other
 
—

 
22

 
—

 
22

 
 
Total nuclear decommissioning trust fund
 
$
368

 
$
189

 
$
—

 
$
557

(b) 
 
Total Ameren
 
$
368

 
$
190

 
$
17

 
$
575

 
Ameren Missouri
Derivative assets – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Natural gas
 
$
—

 
$
—

 
$
1

 
$
1

 
 
Power
 
—

 
—

 
16

 
16

 
 
Total derivative assets – commodity contracts
 
$
—

 
$
—

 
$
17

 
$
17

 
 
Nuclear decommissioning trust fund:
 
 
 
 
 
 
 
 
 
 
Cash and cash equivalents
 
$
4

 
$
—

 
$
—

 
$
4

 
 
Equity securities:
 
 
 
 
 
 
 
 
 
 
U.S. large capitalization
 
364

 
—

 
—

 
364

 
 
Debt securities:
 
 
 
 
 
 
 
 
 
 
U.S. Treasury and agency securities
 
—

 
109

 
—

 
109

 
 
Corporate bonds
 
—

 
58

 
—

 
58

 
 
Other
 
—

 
22

 
—

 
22

 
 
Total nuclear decommissioning trust fund
 
$
368

 
$
189

 
$
—

 
$
557

(b) 
 
Total Ameren Missouri
 
$
368

 
$
189

 
$
17

 
$
574

 
Ameren Illinois
Derivative assets – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Natural gas
 
$
—

 
$
1

 
$
—

 
$
1

 
Liabilities:
 
 
 
 
 
 
 
 
 
 
Ameren
Derivative liabilities – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
29

 
$
—

 
$
—

 
$
29

 
 
Natural gas
 
1

 
62

 
1

 
64

 
 
Power
 
—

 
—

 
170

 
170

 
 
Uranium
 
—

 
—

 
1

 
1

 
 
Total Ameren
 
$
30

 
$
62

 
$
172

 
$
264

 
 
 
 
Quoted Prices in
Active Markets for
Identical Assets
or Liabilities
(Level 1)
 
Significant Other
Observable
Inputs
(Level 2)
 
Significant Other
Unobservable
Inputs
(Level 3)
 
Total
 
Ameren Missouri
Derivative liabilities – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
29

 
$
—

 
$
—

 
$
29

 
 
Natural gas
 
—

 
13

 
1

 
14

 
 
Power
 
—

 
—

 
—

 
—

 
 
Uranium
 
—

 
—

 
1

 
1

 
 
Total Ameren Missouri
 
$
29

 
$
13

 
$
2

 
$
44

 
Ameren Illinois
Derivative liabilities – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Natural gas
 
$
1

 
$
49

 
$
—

 
$
50

 
 
Power
 
—

 
—

 
170

 
170

 
 
Total Ameren Illinois
 
$
1

 
$
49

 
$
170

 
$
220

 
(a)
The derivative asset and liability balances are presented net of counterparty credit considerations.
(b)
Balance excludes $(1) million of receivables, payables, and accrued income, net.
The following table sets forth, by level within the fair value hierarchy, our assets and liabilities measured at fair value on a recurring basis as of December 31, 2014:
 
 
 
Quoted Prices in
Active Markets for
Identical Assets
or Liabilities
(Level 1)
 
Significant Other
Observable Inputs
(Level 2)
 
Significant
Other
Unobservable
Inputs
(Level 3)
 
Total
 
Assets:
 
 
 
 
 
 
 
 
 
 
Ameren
Derivative assets – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
—

 
$
—

 
$
2

 
$
2

 
 
Natural gas
 
—

 
1

 
1

 
2

 
 
Power
 
—

 
4

 
11

 
15

 
 
Total derivative assets – commodity contracts
 
$
—

 
$
5

 
$
14

 
$
19

 
 
Nuclear decommissioning trust fund:
 
 
 
 
 
 
 
 
 
 
Cash and cash equivalents
 
$
1

 
$
—

 
$
—

 
$
1

 
 
Equity securities:
 
 
 
 
 
 
 
 
 
 
U.S. large capitalization
 
364

 
—

 
—

 
364

 
 
Debt securities:
 
 
 
 
 
 
 
 
 
 
U.S. Treasury and agency securities
 
—

 
102

 
—

 
102

 
 
Corporate bonds
 
—

 
63

 
—

 
63

 
 
Other
 
—

 
17

 
—

 
17

 
 
Total nuclear decommissioning trust fund
 
$
365

 
$
182

 
$
—

 
$
547

(b) 
 
Total Ameren
 
$
365

 
$
187

 
$
14

 
$
566

 
Ameren Missouri
Derivative assets – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
—

 
$
—

 
$
2

 
$
2

 
 
Natural gas
 
—

 
1

 
—

 
1

 
 
Power
 
—

 
4

 
11

 
15

 
 
Total derivative assets – commodity contracts
 
$
—

 
$
5

 
$
13

 
$
18

 
 
Nuclear decommissioning trust fund:
 
 
 
 
 
 
 
 
 
 
Cash and cash equivalents
 
$
1

 
$
—

 
$
—

 
$
1

 
 
Equity securities:
 
 
 
 
 
 
 
 
 
 
U.S. large capitalization
 
364

 
—

 
—

 
364

 
 
Debt securities:
 
 
 
 
 
 
 
 
 
 
U.S. Treasury and agency securities
 
—

 
102

 
—

 
102

 
 
Corporate bonds
 
—

 
63

 
—

 
63

 
 
Other
 
—

 
17

 
—

 
17

 
 
Total nuclear decommissioning trust fund
 
$
365

 
$
182

 
$
—

 
$
547

(b) 
 
Total Ameren Missouri
 
$
365

 
$
187

 
$
13

 
$
565

 
Ameren Illinois
Derivative assets – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Natural gas
 
$
—

 
$
—

 
$
1

 
$
1

 
 
 
 
Quoted Prices in
Active Markets for
Identical Assets
or Liabilities
(Level 1)
 
Significant Other
Observable Inputs
(Level 2)
 
Significant
Other
Unobservable
Inputs
(Level 3)
 
Total
 
Liabilities:
 
 
 
 
 
 
 
 
 
 
Ameren
Derivative liabilities – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
21

 
$
—

 
$
8

 
$
29

 
 
Natural gas
 
1

 
53

 
2

 
56

 
 
Power
 
—

 
1

 
144

 
145

 
 
Uranium
 
—

 
—

 
2

 
2

 
 
Total Ameren
 
$
22

 
$
54

 
$
156

 
$
232

 
Ameren Missouri
Derivative liabilities – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
21

 
$
—

 
$
8

 
$
29

 
 
Natural gas
 
1

 
10

 
1

 
12

 
 
Power
 
—

 
1

 
2

 
3

 
 
Uranium
 
—

 
—

 
2

 
2

 
 
Total Ameren Missouri
 
$
22

 
$
11

 
$
13

 
$
46

 
Ameren Illinois
Derivative liabilities – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Natural gas
 
$
—

 
$
43

 
$
1

 
$
44

 
 
Power
 
—

 
—

 
142

 
142

 
 
Total Ameren Illinois
 
$
—

 
$
43

 
$
143

 
$
186

 
(a)
The derivative asset and liability balances are presented net of counterparty credit considerations.
(b)
Balance excludes $2 million of receivables, payables, and accrued income, net.

Schedule Of Changes In The Fair Value Of Financial Assets And Liabilities Classified As Level 3 In The Fair Value Hierarchy 
The following table summarizes the changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the year ended December 31, 2015:
  
 
Net Derivative Commodity Contracts
  
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
Fuel oils:
 
 
 
 
 
 
Beginning balance at January 1, 2015
$
(6
)
$
(a)

$
(6
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities:
 
(1
)
 
(a)

 
(1
)
Settlements
 
5

 
(a)

 
5

Transfers out of Level 3
 
2

 
(a)

 
2

Ending balance at December 31, 2015
$
—

$
(a)

$
—

Change in unrealized gains (losses) related to assets/liabilities held at December 31, 2015
$
—

$
(a)

$
—

Natural gas:
 
 
 
 
 
 
Beginning balance at January 1, 2015
$
(1
)
$
—

$
(1
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities:

 
—

 
1

 
1

Settlements
 
1

 
(1
)
 
—

Ending balance at December 31, 2015
$
—

$
—

$
—

Change in unrealized gains (losses) related to assets/liabilities held at December 31, 2015
$
—

$
—

$
—

Power:
 
 
 
 
 
 
Beginning balance at January 1, 2015
$
9

$
(142
)
$
(133
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities:

 
2

 
(41
)
 
(39
)
Purchases
 
29

 
—

 
29

Settlements
 
(23
)
 
13

 
(10
)
Transfers out of Level 3
 
(1
)
 
—

 
(1
)
Ending balance at December 31, 2015
$
16

$
(170
)
$
(154
)
Change in unrealized gains (losses) related to assets/liabilities held at December 31, 2015
$
—

$
(39
)
$
(39
)
Uranium:
 
 
 
 
 
 
Beginning balance at January 1, 2015
$
(2
)
$
(a)

$
(2
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities:

 
(1
)
 
(a)

 
(1
)
Settlements
 
2

 
(a)

 
2

Ending balance at December 31, 2015
$
(1
)
$
(a)

$
(1
)
Change in unrealized gains (losses) related to assets/liabilities held at December 31, 2015
$
—

$
(a)

$
—

(a)
Not applicable.
The following table summarizes the changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the year ended December 31, 2014:
  
 
Net Derivative Commodity Contracts
  
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
Fuel oils:
 
 
 
 
 
 
Beginning balance at January 1, 2014
$
5

$
(a)

$
5

Realized and unrealized gains (losses) included in regulatory assets/liabilities:

 
(9
)
 
(a)

 
(9
)
Settlements
 
(2
)
 
(a)

 
(2
)
Ending balance at December 31, 2014
$
(6
)
$
(a)

$
(6
)
Change in unrealized gains (losses) related to assets/liabilities held at December 31, 2014
$
(6
)
$
(a)

$
(6
)
Natural gas:
 
 
 
 
 
 
Beginning balance at January 1, 2014
$
—

$
—

$
—

Realized and unrealized gains (losses) included in regulatory assets/liabilities:

 
—

 
1

 
1

Purchases
 
—

 
(2
)
 
(2
)
Sales
 
(1
)
 
—

 
(1
)
Settlements
 
—

 
1

 
1

Ending balance at December 31, 2014
$
(1
)
$
—

$
(1
)
Change in unrealized gains (losses) related to assets/liabilities held at December 31, 2014
$
—

$
2

$
2

Power:
 
 
 
 
 
 
Beginning balance at January 1, 2014
$
19

$
(108
)
$
(89
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities:

 
(14
)
 
(39
)
 
(53
)
Purchases
 
34

 
—

 
34

Sales
 
(1
)
 
—

 
(1
)
Settlements
 
(29
)
 
5

 
(24
)
Ending balance at December 31, 2014
$
9

$
(142
)
$
(133
)
Change in unrealized gains (losses) related to assets/liabilities held at December 31, 2014
$
—

$
(43
)
$
(43
)
Uranium:
 
 
 
 
 
 
Beginning balance at January 1, 2014
$
(6
)
$
(a)

$
(6
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities:

 
(1
)
 
(a)

 
(1
)
Settlements
 
5

 
(a)

 
5

Ending balance at December 31, 2014
$
(2
)
$
(a)

$
(2
)
Change in unrealized gains (losses) related to assets/liabilities held at December 31, 2014
$
(1
)
$
(a)

$
(1
)
(a)
Not applicable.
Schedule Of Carrying Amounts And Estimated Fair Values Of Long-Term Debt And Preferred Stock 
following table presents the carrying amounts and estimated fair values of our long-term debt, capital lease obligations and preferred stock at December 31, 2015 and 2014:
  
2015
 
2014
  
Carrying Amount
 
Fair Value
 
Carrying Amount
 
Fair Value
Ameren:(a)
 
 
 
 
 
 
 
Long-term debt and capital lease obligations (including current portion)(b)
$
7,275

 
$
7,814

 
$
6,205

 
$
7,135

Preferred stock
142

 
125

 
142

 
122

Ameren Missouri:
 
 
 
 
 
 
 
Long-term debt and capital lease obligations (including current portion)(b)
$
4,110

 
$
4,449

 
$
3,981

 
$
4,518

Preferred stock
80

 
75

 
80

 
73

Ameren Illinois:
 
 
 
 
 
 
 
Long-term debt (including current portion)(b)
$
2,471

 
$
2,665

 
$
2,224

 
$
2,517

Preferred stock
62

 
50

 
62

 
49

(a)
Preferred stock is recorded in "Noncontrolling Interests" on the consolidated balance sheet.
Nuclear Decommissioning Trust Fund Investments (Tables)
Fair Value Of Securities In Nuclear Decommissioning Trust Fund 
The following table presents the costs and fair values of investments in debt and equity securities in Ameren's and Ameren Missouri’s nuclear decommissioning trust fund at December 31, 2015 and 2014:
Security Type
Cost
 
Gross Unrealized Gain
 
Gross Unrealized Loss
 
Fair Value
2015
 
 
 
 
 
 
 
Debt securities
$
191

 
$
2

$
4

 
$
189

Equity securities
147

 
224

 
7

 
364

Cash
4

 
—

 
—

 
4

Other(a)
(1
)
 
—

 
—

 
(1
)
Total
$
341

 
$
226

$
11

 
$
556

2014
 
 
 
 
 
 
 
Debt securities
$
175

 
$
7

$
—

 
$
182

Equity securities
138

 
230

 
4

 
364

Cash
1

 
—

 
—

 
1

Other(a)
2

 
—

 
—

 
2

Total
$
316

 
$
237

$
4

 
$
549


(a)
Represents payables relating to pending security purchases, net of receivables related to pending security sales and interest.
Schedule Of Unrealized Losses On Available-For-Sale Investments Included In Nuclear Decommissioning Trust Fund 
The following table presents the fair value and the gross unrealized losses of the available-for-sale securities held in Ameren's and Ameren Missouri's nuclear decommissioning trust fund. They are aggregated by investment category and the length of time that individual securities have been in a continuous unrealized loss position at December 31, 2015:
  
Less than 12 Months
 
 
12 Months or Greater
 
Total
  
Fair Value
 
Gross
Unrealized
Losses
 
 
Fair Value
 
Gross
Unrealized
Losses
 
Fair Value
 
Gross
Unrealized
Losses
Debt securities
$
136

$
3

 
 
$
4

$
1

 
$
140

$
4

Equity securities
16

 
3

 
 
4

 
4

 
20

 
7

Total
$
152

$
6

 
 
$
8

$
5

 
$
160

$
11

Proceeds From Sale Of Investments In Nuclear Decommissioning Trust Fund And Gross Realized Gains And Losses 
The following table presents proceeds from the sale and maturities of investments in Ameren Missouri’s nuclear decommissioning trust fund and the gross realized gains and losses resulting from those sales for the years ended December 31, 2015, 2014, and 2013:
 
2015
 
2014
 
2013
Proceeds from sales and maturities
$
349

 
$
391

 
$
196

Gross realized gains
8

 
7

 
7

Gross realized losses
2

 
2

 
5

Fair Value Of Securities In Nuclear Decommissioning Trust Fund According To Their Contractual Maturities 
The following table presents the costs and fair values of investments in debt securities in Ameren's and Ameren Missouri’s nuclear decommissioning trust fund according to their contractual maturities at December 31, 2015:
 
Cost
 
Fair Value
Less than 5 years
$
106

 
$
105

5 years to 10 years
42

 
41

Due after 10 years
43

 
43

Total
$
191

 
$
189

Retirement Benefits (Tables)
Summary Of Benefit Liability Recorded 
The following table presents the net benefit liability recorded on the balance sheets of each of the Ameren Companies as of December 31, 2015 and 2014:
 
2015

2014

Ameren(a)
$
567

$
710

Ameren Missouri
236

277

Ameren Illinois
219

278

(a)
Includes amounts for Ameren registrant and nonregistrant subsidiaries.
Funded Status Of Benefit Plans And Amounts Included In Regulatory Assets And OCI 
The following table presents the funded status of Ameren's pension and postretirement benefit plans as of December 31, 2015 and 2014. It also provides the amounts included in regulatory assets and accumulated OCI at December 31, 2015 and 2014, that have not been recognized in net periodic benefit costs.
  
2015
 
2014
  
Pension Benefits(a)
 
Postretirement
Benefits(a)
 
Pension Benefits(a)
 
Postretirement
Benefits(a)
Accumulated benefit obligation at end of year
$
3,995

$
(b)

 
$
4,176

$
(b)

Change in benefit obligation:
 
 
 
 
 
 
 
Net benefit obligation at beginning of year
$
4,410

$
1,203

 
$
3,900

$
1,096

Service cost
92

 
24

 
79

 
19

Interest cost
174

 
48

 
183

 
50

Participant contributions
—

 
8

 
—

 
16

Actuarial (gain) loss
(256
)
 
(133
)
 
462

 
84

Settlement
(2
)
 
—

 
—

 
—

Benefits paid
(221
)
 
(56
)
 
(214
)
 
(65
)
Federal subsidy on benefits paid
(b)

 
—

 
(b)

 
3

Net benefit obligation at end of year
4,197

 
1,094

 
4,410

 
1,203

Change in plan assets:
 
 
 
 
 
 
 
Fair value of plan assets at beginning of year
3,794

 
1,109

 
3,461

 
1,074

Actual return on plan assets
(29
)
 
(8
)
 
448

 
75

Employer contributions
111

 
18

 
99

 
6

Federal subsidy on benefits paid
(b)

 
—

 
(b)

 
3

Participant contributions
—

 
8

 
—

 
16

Settlements
(2
)
 
—

 
—

 
—

Benefits paid
(221
)
 
(56
)
 
(214
)
 
(65
)
Fair value of plan assets at end of year
3,653

 
1,071

 
3,794

 
1,109

Funded status – deficiency
544

 
23

 
616

 
94

Accrued benefit cost at December 31
$
544

$
23

 
$
616

$
94

Amounts recognized in the balance sheet consist of:
 
 
 
 
 
 
 
Noncurrent asset(c)
$
—

$
(18
)
 
$
—

$
—

Current liability(d)
3

 
2

 
3

 
2

Noncurrent liability
541

 
39

 
613

 
92

Net liability recognized
$
544

$
23

 
$
616

$
94

Amounts recognized in regulatory assets consist of:
 
 
 
 
 
 
 
Net actuarial (gain) loss
$
395

$
(82
)
 
$
452

$
(7
)
Prior service cost (credit)
(5
)
 
(11
)
 
(6
)
 
(16
)
Amounts (pretax) recognized in accumulated OCI consist of:
 
 
 
 
 
 
 
Net actuarial (gain) loss
17

 
(3
)
 
29

 
(5
)
Prior service cost (credit)
—

 
—

 
—

 
(1
)
Total
$
407

$
(96
)
 
$
475

$
(29
)
(a)
Includes amounts for Ameren registrant and nonregistrant subsidiaries.
(b)
Not applicable.
(c)
Included in "Other assets" on Ameren's consolidated balance sheet.
(d)
Included in "Other current liabilities" on Ameren's consolidated balance sheet.
Assumptions Used To Determine Benefit Obligations 
The following table presents the assumptions used to determine our benefit obligations at December 31, 2015 and 2014:
  
Pension Benefits
 
Postretirement Benefits
  
2015
 
2014
 
2015
 
2014
Discount rate at measurement date
4.50
%
 
4.00
%
 
4.50
%
 
4.00
%
Increase in future compensation
3.50

 
3.50

 
3.50

 
3.50

Medical cost trend rate (initial)
(a)

 
(a)

 
5.00

 
5.00

Medical cost trend rate (ultimate)
(a)

 
(a)

 
5.00

 
5.00

Years to ultimate rate
(a)

 
(a)

 
—

 
—


(a)
Not applicable
Schedule Of Cash Contributions Made To Benefit Plans 
The following table presents the cash contributions made to our defined benefit retirement plan and to our postretirement plans during 2015, 2014, and 2013:
  
Pension Benefits
 
Postretirement Benefits
  
2015
 
2014
 
2013
 
2015
 
2014
 
2013
Ameren Missouri
$
47

 
$
41

 
$
60

 
$
8

 
$
3

 
$
10

Ameren Illinois
45

 
39

 
50

 
8

 
2

 
11

Other
19

 
19

 
46

 
2

 
1

 
4

Ameren(a)
111

 
99

 
156

 
18

 
6

 
25

(a)
Includes amounts for Ameren registrant and nonregistrant subsidiaries.
Target Allocation Of The Plans' Asset Categories 
The following table presents our target allocations for 2016 and our pension and postretirement plans’ asset categories as of December 31, 2015 and 2014:
Asset
Category
Target Allocation
2016
 
Percentage of Plan Assets at December  31,
2015
 
2014
Pension Plan:
 
 
 
 
 
Cash and cash equivalents
0% – 5%
 
1
%
 
2
%
Equity securities:
 
 
 
 
 
U.S. large-capitalization
29% – 39%
 
34
%
 
34
%
U.S. small- and mid-capitalization
3% – 13%
 
7
%
 
7
%
International and emerging markets
9% – 19%
 
13
%
 
12
%
Total equity
51% – 61%
 
54
%
 
53
%
Debt securities
35% – 45%
 
40
%
 
41
%
Real estate
0% –  9%  
 
5
%
 
4
%
Private equity
0% –  5%  
 
(a)

 
(a)

Total
 
 
100
%
 
100
%
Postretirement Plans:
 
 
 
 
 
Cash and cash equivalents
0% – 7%
 
4
%
 
4
%
Equity securities:
 
 
 
 
 
U.S. large-capitalization
34% – 44%
 
39
%
 
40
%
U.S. small- and mid-capitalization
2% – 12%
 
7
%
 
7
%
International
9% – 19%
 
13
%
 
13
%
Total equity
55% – 65%
 
59
%
 
60
%
Debt securities
33% – 43%
 
37
%
 
36
%
Total
 
 
100
%
 
100
%

(a)
Less than 1% of plan assets.
Changes In The Fair Value Of Plan Assets Classified As Level 3 
The following table summarizes the changes in the fair value of the pension plan assets classified as Level 3 in the fair value hierarchy for each of the years ended December 31, 2015 and 2014:
 
Beginning
Balance at
January 1,
 
Actual Return on
Plan Assets Related
to Assets Still Held
at the Reporting Date
 
Actual Return on
Plan Assets Related
to Assets Sold
During the Period
 
Purchases,
Sales, and
Settlements, Net
 
Net
Transfers
into (out of)
of Level 3
 
Ending Balance at
December 31,
2015:
 
 
 
 
 
 
 
 
 
 
 
Real estate
$
147

 
$
14

 
$
—

 
$
7

 
$
—

 
$
168

Private equity
13

 
(9
)
 
9

 
(5
)
 
—

 
8

2014:
 
 
 
 
 
 
 
 
 
 
 
Real estate
$
131

 
$
11

 
$
—

 
$
5

 
$
—

 
$
147

Private equity
15

 
(9
)
 
10

 
(3
)
 
—

 
13

Components Of Net Periodic Benefit Cost 
The following table presents the components of the net periodic benefit cost of Ameren's pension and postretirement benefit plans during 2015, 2014, and 2013:
 
Pension Benefits(a)
 
Postretirement Benefits(a)
2015
 
 
 
Service cost
$
92

 
$
24

Interest cost
174

 
48

Expected return on plan assets
(248
)
 
(68
)
Amortization of:
 
 
 
Prior service credit
(1
)
 
(5
)
Actuarial loss
74

 
5

Settlement Loss
1

 
—

Net periodic benefit cost
$
92

 
$
4

2014
 
 
 
Service cost
$
79

 
$
19

Interest cost
183

 
50

Expected return on plan assets
(229
)
 
(65
)
Amortization of:
 
 
 
Prior service credit
(1
)
 
(5
)
Actuarial (gain) loss
49

 
(7
)
Net periodic benefit cost (benefit)
$
81

 
$
(8
)
2013
 
 
 
Service cost
$
91

 
$
22

Interest cost
163

 
46

Expected return on plan assets
(218
)
 
(62
)
Amortization of:
 
 
 
Prior service credit
(2
)
 
(6
)
Actuarial loss
87

 
8

Curtailment gain
(12
)
 
(7
)
Net periodic benefit cost(b)
$
109

 
$
1

(a)
Includes amounts for Ameren registrant and nonregistrant subsidiaries.
(b)
The net periodic benefit cost includes a $6 million and a $7 million net gain for pension benefits and postretirement benefits, respectively, which was included in "Income (loss) from discontinued operations, net of taxes" on Ameren's consolidated statement of income (loss). This net gain includes the curtailment gain recognized in 2013 as a result of a significant reduction in employees as of the December 2, 2013 closing date of the New AER divestiture. See Note 16 – Divestiture Transactions and Discontinued Operations for additional information on the divestiture.
Summary Of Estimated Amortizable Amounts From Regulatory Assets and Accumulated OCI Into Net Periodic Benefit Cost 
The estimated amounts that will be amortized from regulatory assets and accumulated OCI into Ameren's net periodic benefit cost in 2016 are as follows:
  
Pension Benefits(a)
 
Postretirement Benefits(a)
Regulatory assets:
 
 
 
Prior service credit
$
(1
)
 
$
(4
)
Net actuarial loss
46

 
(3
)
Accumulated OCI:
 
 
 
Net actuarial (gain) loss
(3
)
 
(2
)
Total
$
42

 
$
(9
)
(a)
Includes amounts for Ameren registrant and nonregistrant subsidiaries.
Summary Of Benefit Plan Costs Incurred 
The Ameren Companies are responsible for their share of the pension and postretirement benefit costs. The following table presents the pension costs and the postretirement benefit costs incurred and included in continuing operations for the years ended December 31, 2015, 2014, and 2013:
  
Pension Costs
 
Postretirement Costs
  
2015
 
2014
 
2013
 
2015
 
2014
 
2013
Ameren Missouri(a)
$
54

 
$
50

 
$
69

 
$
8

 
$
3

 
$
8

Ameren Illinois
38

 
30

 
41

 
(3
)
 
(9
)
 
—

Other
—

 
1

 
5

 
(1
)
 
(2
)
 
—

Ameren(b)
92

 
81

 
115

 
4

 
(8
)
 
8

(a)
Does not include the impact of the regulatory tracking mechanism for the difference between the level of pension and postretirement benefit costs incurred by Ameren Missouri under GAAP and the level of such costs included in rates.
(b)
Includes amounts for Ameren registrant and nonregistrant subsidiaries.
Schedule Of Expected Payments From Qualified Trust And Company Funds 
The expected pension and postretirement benefit payments from qualified trust and company funds, which reflect expected future service, as of December 31, 2015, are as follows:
  
Pension Benefits
 
Postretirement Benefits
  
Paid from
Qualified
Trust Funds
 
        Paid from
         Company
      Funds
 
        Paid from
         Qualified
      Trust Funds
 
        Paid from
         Company
      Funds
2016
$
233

 
$
3

 
$
55

 
$
2

2017
244

 
3

 
58

 
2

2018
250

 
3

 
60

 
2

2019
257

 
3

 
62

 
2

2020
261

 
3

 
65

 
2

2021 – 2025
1,377

 
13

 
341

 
12

Assumptions Used To Determine Net Periodic Benefit Cost 
The following table presents the assumptions used to determine net periodic benefit cost for our pension and postretirement benefit plans for the years ended December 31, 2015, 2014, and 2013:
  
Pension Benefits
 
Postretirement Benefits
  
2015
 
2014
 
2013
 
2015
 
2014
 
2013
Discount rate at measurement date
4.00
%
 
4.75
%
 
4.00
%
 
4.00
%
 
4.75
%
 
4.00
%
Expected return on plan assets
7.25

 
7.25

 
7.50

 
7.00

 
7.00

 
7.25

Increase in future compensation
3.50

 
3.50

 
3.50

 
3.50

 
3.50

 
3.50

Medical cost trend rate (initial)
(a)

 
(a)

 
(a)

 
5.00

 
5.00

 
5.00

Medical cost trend rate (ultimate)
(a)

 
(a)

 
(a)

 
5.00

 
5.00

 
5.00

Years to ultimate rate
(a)

 
(a)

 
(a)

 
—

 
—

 
—


(a)
Not applicable
Schedule Of Potential Changes In Key Assumptions 
The table below reflects the sensitivity of Ameren’s plans to potential changes in key assumptions:
  
Pension Benefits
 
Postretirement Benefits
  
Service Cost
and Interest
Cost
 
    Projected
    Benefit
     Obligation
 
    Service Cost
    and Interest
    Cost
 
    Postretirement
      Benefit
       Obligation
0.25% decrease in discount rate
$
(1
)
 
$
130

 
$
1

 
$
37

0.25% increase in salary scale
2

 
14

 
—

 
—

1.00% increase in annual medical trend
—

 
—

 
3

 
44

1.00% decrease in annual medical trend
—

 
—

 
(3
)
 
(44
)
Schedule Of Matching Contributions 
The following table presents the portion of the matching contribution to the Ameren 401(k) plan attributable to the continuing operations for each of the Ameren Companies for the years ended December 31, 2015, 2014, and 2013:
 
2015
 
2014
 
2013
Ameren Missouri
$
16

 
$
16

 
$
16

Ameren Illinois
12

 
11

 
10

Other
1

 
1

 
1

Ameren(a)
29

 
28

 
27

(a)
Includes amounts for Ameren registrant and nonregistrant subsidiaries.
Target Allocation Of The Plans' Asset Categories 
The following table sets forth, by level within the fair value hierarchy discussed in Note 8 – Fair Value Measurements, the pension plan assets measured at fair value as of December 31, 2015:
 
Quoted Prices in
Active Markets for
Identified Assets
(Level 1)
 
Significant Other
Observable Inputs
(Level 2)
 
Significant Other
Unobservable
Inputs
(Level 3)
 
Total
Cash and cash equivalents
$
—

 
$
20

 
$
—

 
$
20

Equity securities:
 
 
 
 
 
 
 
U.S. large-capitalization
—

 
1,296

 
—

 
1,296

U.S. small- and mid-capitalization
268

 
—

 
—

 
268

International and emerging markets
122

 
369

 
—

 
491

Debt securities:
 
 
 
 
 
 
 
Corporate bonds
—

 
631

 
—

 
631

Municipal bonds
—

 
104

 
—

 
104

U.S. Treasury and agency securities
6

 
751

 
—

 
757

Other
—

 
5

 
—

 
5

Real estate
—

 
—

 
168

 
168

Private equity
—

 
—

 
8

 
8

Total
$
396

 
$
3,176

 
$
176

 
$
3,748

Less: Medical benefit assets at December 31(a)
 
 
 
 
 
 
(123
)
Plus: Net receivables at December 31(b)
 
 
 
 
 
 
28

Fair value of pension plans assets at year end
 
 
 
 
 
 
$
3,653

(a)
Medical benefit (health and welfare) component for accounts maintained in accordance with Section 401(h) of the Internal Revenue Code to fund a portion of the postretirement obligation.
(b)
Receivables related to pending security sales, offset by payables related to pending security purchases.
The following table sets forth, by level within the fair value hierarchy discussed in Note 8 – Fair Value Measurements, the pension plan assets measured at fair value as of December 31, 2014:
 
Quoted Prices in
Active Markets for
Identified Assets or Liabilities
(Level 1)
 
Significant Other
Observable Inputs
(Level 2)
 
Significant Other
Unobservable
Inputs
(Level 3)
 
Total
Cash and cash equivalents
$
—

 
$
38

 
$
—

 
$
38

Equity securities:
 
 
 
 
 
 
 
U.S. large-capitalization
—

 
1,331

 
—

 
1,331

U.S. small- and mid-capitalization
270

 
—

 
—

 
270

International and emerging markets
134

 
360

 
—

 
494

Debt securities:
 
 
 
 
 
 
 
Corporate bonds
—

 
1,026

 
—

 
1,026

Municipal bonds
—

 
175

 
—

 
175

U.S. Treasury and agency securities
6

 
366

 
—

 
372

Other
—

 
31

 
—

 
31

Real estate
—

 
—

 
147

 
147

Private equity
—

 
—

 
13

 
13

Derivative assets
1

 
—

 
—

 
1

Total
$
411

 
$
3,327

 
$
160

 
$
3,898

Less: Medical benefit assets at December 31(a)
 
 
 
 
 
 
(125
)
Plus: Net receivables at December 31(b)
 
 
 
 
 
 
21

Fair value of pension plans assets at year end
 
 
 
 
 
 
$
3,794

(a)
Medical benefit (health and welfare) component for accounts maintained in accordance with Section 401(h) of the Internal Revenue Code to fund a portion of the postretirement obligation.
(b)
Receivables related to pending security sales, offset by payables related to pending security purchases.
Target Allocation Of The Plans' Asset Categories 
The following table sets forth, by level within the fair value hierarchy discussed in Note 8 – Fair Value Measurements, the postretirement benefit plans assets measured at fair value as of December 31, 2015:
 
Quoted Prices in
Active Markets for
Identified Assets
(Level 1)
 
Significant Other
Observable Inputs
(Level 2)
 
Significant Other
Unobservable
Inputs
(Level 3)
 
Total
Cash and cash equivalents
$
61

 
$
—

 
$
—

 
$
61

Equity securities:
 
 
 
 
 
 
 
U.S. large-capitalization
272

 
98

 
—

 
370

U.S. small- and mid-capitalization
65

 
—

 
—

 
65

International
33

 
93

 
—

 
126

Other
—

 
7

 
—

 
7

Debt securities:
 
 
 
 
 
 
 
Corporate bonds
—

 
138

 
—

 
138

Municipal bonds
—

 
114

 
—

 
114

U.S. Treasury and agency securities
—

 
55

 
—

 
55

Other
—

 
40

 
—

 
40

Total
$
431

 
$
545

 
$
—

 
$
976

Plus: Medical benefit assets at December 31(a)
 
 
 
 
 
 
123

Less: Net payables at December 31(b)
 
 
 
 
 
 
(28
)
Fair value of postretirement benefit plans assets at year end
 
 
 
 
 
 
$
1,071

(a)
Medical benefit (health and welfare) component for 401(h) accounts to fund a portion of the postretirement obligation. These 401(h) assets are included in the pension plan assets shown above.
(b)
Payables related to pending security purchases, offset by interest receivables and receivables related to pending security sales.
The following table sets forth, by level within the fair value hierarchy discussed in Note 8 – Fair Value Measurements, the postretirement benefit plans assets measured at fair value as of December 31, 2014:
 
Quoted Prices in
Active Markets for
Identified Assets
(Level 1)
 
Significant Other
Observable Inputs
(Level 2)
 
Significant Other
Unobservable
Inputs
(Level 3)
 
Total
Cash and cash equivalents
$
89

 
$
—

 
$
—

 
$
89

Equity securities:
 
 
 
 
 
 
 
U.S. large-capitalization
291

 
101

 
—

 
392

U.S. small- and mid-capitalization
70

 
—

 
—

 
70

International
37

 
94

 
—

 
131

Other
—

 
7

 
—

 
7

Debt securities:
 
 
 
 
 
 
 
Corporate bonds
—

 
105

 
—

 
105

Municipal bonds
—

 
111

 
—

 
111

U.S. Treasury and agency securities
—

 
89

 
—

 
89

Other
—

 
44

 
—

 
44

Total
$
487

 
$
551

 
$
—

 
$
1,038

Plus: Medical benefit assets at December 31(a)
 
 
 
 
 
 
125

Less: Net payables at December 31(b)
 
 
 
 
 
 
(54
)
Fair value of postretirement benefit plans assets at year end
 
 
 
 
 
 
$
1,109

(a)
Medical benefit (health and welfare) component for 401(h) accounts to fund a portion of the postretirement obligation. These 401(h) assets are included in the pension plan assets shown above.
(b)
Payables related to pending security purchases, offset by Medicare, interest receivables, and receivables related to pending security sales.
Stock-Based Compensation (Tables)
Summary Of Nonvested Shares Related To Long-Term Incentive Plan
A summary of nonvested shares at December 31, 2015, and changes during the year ended December 31, 2015, under the 2006 Incentive Plan and the 2014 Incentive Plan are presented below:
  
Performance Share Units
  
Share
Units
 
Weighted-average
Fair Value per Share Unit
Nonvested at January 1, 2015
1,162,377

 
$
35.35

Granted(a)
570,313

 
52.88

Forfeitures
(1,944
)
 
34.75

Earned and vested(b)
(705,876
)
 
33.93

Nonvested at December 31, 2015
1,024,870

 
$
46.08

(a)
Includes performance share units (share units) granted to certain executive and nonexecutive officers and other eligible employees in 2015 under the 2014 Incentive Plan.
(b)
Includes share units granted in 2013 that vested as of December 31, 2015, that were earned pursuant to the terms of the award grants. Also includes share units that vested due to attainment of retirement eligibility by certain employees. Actual shares issued for retirement-eligible employees will vary depending on actual performance over the three-year measurement period.
Income Taxes (Tables)
Schedule Of Effective Income Tax Rate Reconciliation 
The following table presents the principal reasons for the difference between the effective income tax rate and the statutory federal income tax rate for the years ended December 31, 2015, 2014, and 2013:
 
Ameren Missouri
 
Ameren Illinois
 
Ameren
2015
 
 
 
 
 
Statutory federal income tax rate:
35
 %
 
35
 %
 
35
 %
Increases (decreases) from:
 
 
 
 
 
Depreciation differences
—

 
(2
)
 
(1
)
Amortization of investment tax credit
(1
)
 
—

 
(1
)
State tax
3

 
5

 
5

Other permanent items
—

 
(1
)
 
—

Effective income tax rate
37
 %
 
37
 %
 
38
 %
2014
 
 
 
 
 
Statutory federal income tax rate:
35
 %
 
35
 %
 
35
 %
Increases (decreases) from:
 
 
 
 
 
Amortization of investment tax credit
(1
)
 
—

 
(1
)
State tax
3

 
6

 
4

Other permanent items
—

 
—

 
1

Effective income tax rate
37
 %
 
41
 %
 
39
 %
2013
 
 
 
 
 
Statutory federal income tax rate:
35
 %
 
35
 %
 
35
 %
Increases (decreases) from:
 
 
 
 
 
Depreciation differences
—

 
(1
)
 
—

Amortization of investment tax credit
(1
)
 
—

 
(1
)
State tax
3

 
6

 
4

Other permanent items
1

 
—

 
—

Effective income tax rate
38
 %
 
40
 %
 
38
 %
Schedule Of Components Of Income Tax Expense (Benefit) 
The following table presents the components of income tax expense (benefit) for the years ended December 31, 2015, 2014, and 2013:
 
Ameren Missouri
 
Ameren Illinois
 
Other
 
Ameren
2015
 
 
 
 
 
 
 
Current taxes:
 
 
 
 
 
 
 
Federal
$
110

 
$
(83
)
 
$
(29
)
 
$
(2
)
State
17

 
(11
)
 
(10
)
 
(4
)
Deferred taxes:
 
 
 
 
 
 
 
Federal
71

 
193

 
35

 
299

State
16

 
29

 
31

 
76

Deferred investment tax credits, amortization
(5
)
 
(1
)
 
—

 
(6
)
Total income tax expense
$
209

 
$
127

 
$
27

 
$
363

2014
 
 
 
 
 
 
 
Current taxes:
 
 
 
 
 
 
 
Federal
$
(13
)
 
$
(51
)
 
$
27

 
$
(37
)
State
(3
)
 
(2
)
 
(32
)
 
(37
)
Deferred taxes:
 
 
 
 
 
 
 
Federal
222

 
159

 
(12
)
 
369

State
28

 
38

 
22

 
88

Deferred investment tax credits, amortization
(5
)
 
(1
)
 
—

 
(6
)
Total income tax expense
$
229

 
$
143

 
$
5

 
$
377

2013
 
 
 
 
 
 
 
Current taxes:
 
 
 
 
 
 
 
Federal
$
136

 
$
(15
)
 
$
(239
)
(a) 
$
(118
)
State
41

 
21

 
(43
)
(a) 
19

Deferred taxes:
 
 
 
 
 
 
 
Federal
64

 
99

 
205

(a) 
368

State
6

 
6

 
36

(a) 
48

Deferred investment tax credits, amortization
(5
)
 
(1
)
 
—

 
(6
)
Total income tax expense (benefit)
$
242

 
$
110

 
$
(41
)
 
$
311


(a)
These amounts are substantially related to the reversal of unrecognized tax benefits as a result of IRS guidance related to the deductibility of expenditures to maintain, replace, or improve steam or electric power generation property, along with casualty loss deductions for storm damage. The amounts also reflect the increase in deferred tax expense due to available net operating losses.
Schedule Of Deferred Tax Assets And Liabilities Resulting From Temporary Differences 
The following table presents the deferred tax assets and deferred tax liabilities recorded as a result of temporary differences at December 31, 2015 and 2014:
 
Ameren Missouri
 
Ameren Illinois
 
Other
 
Ameren
2015
 
 
 
 
 
 
 
Accumulated deferred income taxes, net liability (asset):
 
 
 
 
 
 
 
Plant related
$
2,931

 
$
1,587

 
$
37

 
$
4,555

Regulatory assets, net
81

 
(1
)
 
—

 
80

Deferred employee benefit costs
(76
)
 
(40
)
 
(91
)
 
(207
)
Revenue requirement reconciliation adjustments

—

 
66

 
—

 
66

Tax carryforwards
(65
)
 
(133
)
 
(405
)
 
(603
)
Other
(27
)
 
1

 
20

 
(6
)
Total net accumulated deferred income tax liabilities (assets) (a)
$
2,844

 
$
1,480

 
$
(439
)
 
$
3,885

2014
 
 
 
 
 
 
 
Accumulated deferred income taxes, net liability (asset):
 
 
 
 
 
 
 
Plant related
$
2,776

 
$
1,393

 
$
16

 
$
4,185

Regulatory assets, net
82

 
(5
)
 
1

 
78

Deferred employee benefit costs
(80
)
 
(45
)
 
(95
)
 
(220
)
Revenue requirement reconciliation adjustments
—

 
66

 
3

 
69

Tax carryforwards
(107
)
 
(139
)
 
(429
)
 
(675
)
Other
86

 
(22
)
 
70

 
134

Total net accumulated deferred income tax liabilities (assets) (a)
$
2,757

 
$
1,248

 
$
(434
)
 
$
3,571


(a)
Reflects the adoption of the new authoritative accounting guidance for the balance sheet classification of deferred income taxes. See Note 1 – Summary of Significant Accounting Policies for additional information.
Schedule Of Net Operating Loss Carryforwards And Tax Credit Carryforwards 

The following table presents the components of deferred tax assets relating to net operating loss carryforwards, tax credit carryforwards, and charitable contribution carryforwards at December 31, 2014:
 
Ameren Missouri
 
Ameren Illinois
 
Other
 
Ameren
Net operating loss carryforwards:
 
 
 
 
 
 
 
Federal(a)
$
75

 
$
127

 
$
255

 
$
457

State(b)
11

 
10

 
53

 
74

Total net operating loss carryforwards
$
86

 
$
137

 
$
308

 
$
531

Tax credit carryforwards:
 
 
 
 
 
 
 
Federal(c)
$
21

 
$
1

 
$
77

 
$
99

State(d)
1

 
2

 
33

 
36

State valuation allowance(e)
(1
)
 
(1
)
 
(2
)
 
(4
)
Total tax credit carryforwards
$
21

 
$
2

 
$
108

 
$
131

Charitable contribution carryforwards(f)
$
—

 
$
—

 
$
19

 
$
19

Valuation allowance(e)
—

 
—

 
(6
)
 
(6
)
Total charitable contribution carryforwards
$
—

 
$
—

 
$
13

 
$
13


(a)
Will begin to expire in 2028
(b)
Will begin to expire in 2019.
(c)
Will begin to expire in 2029.
(d)
Began to expire in 2013.
(e)
See Schedule II under Part IV, Item 15, in this report for information on changes in the valuation allowance.
(f)
Began to expire in 2013.

The following table presents the components of deferred tax assets relating to net operating loss carryforwards, tax credit carryforwards, and charitable contribution carryforwards at December 31, 2015:
 
Ameren Missouri
 
Ameren Illinois
 
Other
 
Ameren
Net operating loss carryforwards:
 
 
 
 
 
 
 
Federal(a)
$
35

 
$
127

 
$
245

 
$
407

State(b)
4

 
4

 
38

 
46

Total net operating loss carryforwards
$
39

 
$
131

 
$
283

 
$
453

Tax credit carryforwards:
 
 
 
 
 
 
 
Federal(c)
$
26

 
$
1

 
$
78

 
$
105

State(d)
—

 
1

 
40

 
41

State valuation allowance(e)
—

 
—

 
(2
)
 
(2
)
Total tax credit carryforwards
$
26

 
$
2

 
$
116

 
$
144

Charitable contribution carryforwards(f)
$
—

 
$
—

 
$
10

 
$
10

Valuation allowance(e)
—

 
—

 
(4
)
 
(4
)
Total charitable contribution carryforwards
$
—

 
$
—

 
$
6

 
$
6


(a)
Will begin to expire in 2029.
(b)
Will begin to expire in 2023.
(c)
Will begin to expire in 2029.
(d)
Will begin to expire in 2016.
(e)
See Schedule II under Part IV, Item 15, in this report for information on changes in the valuation allowance.
(f)
Will begin to expire in 2016.

Schedule Of Changes To Unrecognized Tax Benefits And Related Interest 
A reconciliation of the change in the unrecognized tax benefit balance during the years ended December 31, 2013, 2014, and 2015, is as follows:
 
Ameren Missouri
 
Ameren Illinois
 
Other
 
Ameren
Unrecognized tax benefits – January 1, 2013
$
136

 
$
13

 
$
7

 
$
156

Increases based on tax positions prior to 2013
—

 
2

 
5

 
7

Decreases based on tax positions prior to 2013
(122
)
 
(16
)
 
(5
)
 
(143
)
Increases based on tax positions related to 2013
16

 
—

 
53

(a) 
69

Changes related to settlements with taxing authorities
—

 
—

 
—

 
—

Decreases related to the lapse of statute of limitations
1

 
—

 
—

 
1

Unrecognized tax benefits – December 31, 2013
$
31

 
$
(1
)
 
$
60

 
$
90

Increases based on tax positions prior to 2014
1

 
1

 
4

 
6

Decreases based on tax positions prior to 2014
(32
)
 
(1
)
 
(9
)
 
(42
)
Increases based on tax positions related to 2014
—

 
—

 
—

 
—

Changes related to settlements with taxing authorities
—

 
—

 
—

 
—

Increases related to the lapse of statute of limitations
—

 
—

 
—

 
—

Unrecognized tax benefits – December 31, 2014
$
—

 
$
(1
)
 
$
55

 
$
54

Increases based on tax positions prior to 2015
—

 
1

 
1

 
2

Decreases based on tax positions prior to 2015
—

 
—

 
(56
)
(a) 
(56
)
Increases based on tax positions related to 2015
—

 
—

 
—

 
—

Changes related to settlements with taxing authorities
—

 
—

 
—

 
—

Increases related to the lapse of statute of limitations
—

 
—

 
—

 
—

Unrecognized tax benefits – December 31, 2015
$
—

 
$
—

 
$
—

 
$
—

Total unrecognized tax benefits that, if recognized, would affect the effective tax rates as of December 31, 2013
$
3

 
$
—

 
$
51

(a) 
$
54

Total unrecognized tax benefits (detriments) that, if recognized, would affect the effective tax rates as of December 31, 2014
$
—

 
$
(1
)
 
$
53

(a) 
$
52

Total unrecognized tax benefits that, if recognized, would affect the effective tax rates as of December 31, 2015
$
—

 
$
—

 
$
—

 
$
—


(a)
Primarily due to tax positions relating to the New AER divestiture. The income statement impact of this unrecognized tax benefit was included in "Income (loss) from discontinued operations, net of taxes" on Ameren's consolidated statement of income (loss). See Note 16 – Divestiture Transactions and Discontinued Operations for additional information.
Reconciliation Of Changes In Liability For Interest On Unrecognized Tax Benefits 
A reconciliation of the change in the liability for interest on unrecognized tax benefits during the years ended December 31, 2013, 2014, and 2015, is as follows:
 
Ameren Missouri
 
Ameren Illinois
 
Other
 
Ameren
Liability for interest – January 1, 2013
$
8

 
$
1

 
$
(3
)
 
$
6

Interest charges (income) for 2013
(8
)
 
(1
)
 
4

 
(5
)
Liability for interest – December 31, 2013
$
—

 
$
—

 
$
1

 
$
1

Interest charges (income) for 2014
—

 
—

 
(1
)
 
(1
)
Liability for interest – December 31, 2014
$
—

 
$
—

 
$
—

 
$
—

Interest charges (income) for 2015
—

 
—

 
—

 
—

Liability for interest – December 31, 2015
$
—

 
$
—

 
$
—

 
$
—

Related Party Transactions (Tables)
Schedule of Related Party Transactions
The following table presents the impact on Ameren Missouri and Ameren Illinois of related party transactions for the years ended December 31, 2015, 2014, and 2013. It is based primarily on the agreements discussed above and the money pool arrangements discussed in Note 4 – Short-term Debt and Liquidity.
Agreement
Income Statement Line Item                    
 
  
 
Ameren
Missouri
 
Ameren
Illinois
Ameren Missouri power supply agreements
Operating Revenues
 
2015
$
15

$
(a)

with Ameren Illinois
 
 
2014
 
5

 
(a)

 
 
 
2013
 
3

 
(a)

Ameren Missouri and Ameren Illinois
Operating Revenues
 
2015
 
25

 
4

rent and facility services
 
 
2014
 
21

 
2

 
 
 
2013
 
21

 
1

Ameren Missouri and Ameren Illinois
Operating Revenues
 
2015
 
2

 
(b)

miscellaneous support services
 
 
2014
 
1

 
(b)

 
 
 
2013
 
1

 
3

Total Operating Revenues
 
 
2015
$
42

$
4

 
 
 
2014
 
27

 
2

 
 
 
2013
 
25

 
4

Ameren Illinois power supply
Purchased Power
 
2015
$
(a)

$
15

agreements with Ameren Missouri
 
 
2014
 
(a)

 
5

 
 
 
2013
 
(a)

 
3

Ameren Illinois transmission
Purchased Power
 
2015
 
(a)

 
2

services with ATXI
 
 
2014
 
(a)

 
2

 
 
 
2013
 
(a)

 
2

Total Purchased Power
 
 
2015
$
(a)

$
17

 
 
 
2014
 
(a)

 
7

 
 
 
2013
 
(a)

 
5

Ameren Services support services
Other Operations and
 
2015
$
131

$
119

agreement
Maintenance
 
2014
 
124

 
109

 
 
 
2013
 
116

 
93

Total Other Operations and
 
 
2015
$
131

$
119

Maintenance Expenses
 
 
2014
 
124

 
109

 
 
 
2013
 
116

 
93

Money pool borrowings (advances)
Interest (Charges)
 
2015
$
(b)

$
(b)

 
Income
 
2014
 
(b)

 
(b)

 
 
 
2013
 
(b)

 
(b)

(a)
Not applicable.
(b)
Amount less than $1 million.

Commitments And Contingencies (Tables)
Schedule Of Insurance Coverage At Callaway Energy Center 
The following table presents insurance coverage at Ameren Missouri’s Callaway energy center at December 31, 2015. The property coverage and the nuclear liability coverage must be renewed on April 1 and January 1, respectively, of each year.
Type and Source of Coverage
Maximum Coverages
 
Maximum Assessments
 
Public liability and nuclear worker liability:
 
 
 
 
American Nuclear Insurers
$
375


$
—

 
Pool participation
13,114

(a)  
127

(b)  
 
$
13,489

(c)  
$
127

 
Property damage:
 
 
 
 
Nuclear Electric Insurance Limited
$
2,750

(d)  
$
27

(e)  
European Mutual Association for Nuclear Insurance
500

(f)  
—

 
 
$
3,250

 
$
27

 
Replacement power:
 
 
 
 
Nuclear Electric Insurance Limited
$
490

(g)  
$
10

(e)  

(a)
Provided through mandatory participation in an industrywide retrospective premium assessment program.
(b)
Retrospective premium under the Price-Anderson Act. This is subject to retrospective assessment with respect to a covered loss in excess of $375 million in the event of an incident at any licensed United States commercial reactor, payable at $19 million per year.
(c)
Limit of liability for each incident under the Price-Anderson liability provisions of the Atomic Energy Act of 1954, as amended. A company could be assessed up to $127 million per incident for each licensed reactor it operates, with a maximum of $19 million per incident to be paid in a calendar year for each reactor. This limit is subject to change to account for the effects of inflation and changes in the number of licensed reactors.
(d)
NEIL provides $2.25 billion in property damage, decontamination, and premature decommissioning insurance for both radiation and nonradiation events. An additional $500 million is provided for radiation events only for a total of $2.75 billion.
(e)
All NEIL-insured plants could be subject to assessments should losses exceed the accumulated funds from NEIL.
(f)
European Mutual Association for Nuclear Insurance provides $500 million in excess of the $2.75 billion and $2.25 billion property coverage for radiation and nonradiation events, respectively, provided by NEIL.
(g)
Provides replacement power cost insurance in the event of a prolonged accidental outage. Weekly indemnity is up to $4.5 million for 52 weeks, which commences after the first twelve weeks of an outage, plus up to $3.6 million per week for a minimum of 71 weeks thereafter, for a total not exceeding the policy limit of $490 million. Nonradiation events are sub-limited to $328 million.
Schedule Of Lease Obligations 
We lease various facilities, office equipment, plant equipment, and rail cars under capital and operating leases. The following table presents our lease obligations at December 31, 2015:
 
2016
 
2017
 
2018
 
2019
 
2020
 
After 5 Years
 
Total
Ameren:(a)
 
 
 
 
 
 
 
 
 
 
 
 
 
Minimum capital lease payments(b)
$
33

 
$
33

 
$
32

 
$
32

 
$
32

 
$
329

 
$
491

Less amount representing interest
27

 
27

 
26

 
25

 
25

 
73

 
203

Present value of minimum capital lease payments
$
6

 
$
6

 
$
6

 
$
7

 
$
7

 
$
256

 
$
288

Operating leases(c)
14

 
13

 
12

 
12

 
11

 
30

 
92

Total lease obligations
$
20

 
$
19

 
$
18

 
$
19

 
$
18

 
$
286

 
$
380

Ameren Missouri:
 
 
 
 
 
 
 
 
 
 
 
 
 
Minimum capital lease payments(b)
$
33

 
$
33

 
$
32

 
$
32

 
$
32

 
$
329

 
$
491

Less amount representing interest
27

 
27

 
26

 
25

 
25

 
73

 
203

Present value of minimum capital lease payments
$
6

 
$
6

 
$
6

 
$
7

 
$
7

 
$
256

 
$
288

Operating leases(c)
12

 
11

 
11

 
11

 
10

 
29

 
84

Total lease obligations
$
18

 
$
17

 
$
17

 
$
18

 
$
17

 
$
285

 
$
372

Ameren Illinois:
 
 
 
 
 
 
 
 
 
 
 
 
 
Operating leases(c)
$
1

 
$
1

 
$
1

 
$
1

 
$
1

 
$
1

 
$
6

(a)
Includes amounts for Ameren registrant and nonregistrant subsidiaries and intercompany eliminations.
(b)
See Properties under Part I, Item 2, and Note 3 – Property and Plant, Net, of this report for additional information.
(c)
Amounts related to certain land-related leases have indefinite payment periods. The annual obligations of $3 million, $2 million, and $1 million for Ameren, Ameren Missouri, and Ameren Illinois for these items are included in the 2016 through 2020 columns, respectively.
Schedule Of Rental Expense 
The following table presents total rental expense included in operating expenses for the years ended December 31, 2015, 2014, and 2013:
 
2015
 
2014
 
2013
Ameren(a)
$
36

 
$
37

 
$
32

Ameren Missouri
34

 
32

 
29

Ameren Illinois
28

 
25

 
21

(a)
Includes amounts for Ameren registrant and nonregistrant subsidiaries and intercompany eliminations.
Schedule Of Estimated Purchased Commitments 
December 31, 2015. Ameren’s and Ameren Missouri’s purchased power commitments include a 102-megawatt power purchase agreement with a wind farm operator, which expires in 2024. Ameren’s and Ameren Illinois’ purchased power commitments include the Ameren Illinois power purchase agreements entered into as part of the IPA-administered power procurement process. Included in the Other column are minimum purchase commitments under contracts for equipment, design and construction, and meter reading services at December 31, 2015.
 
Coal
 
Natural
Gas(a)
 
Nuclear
Fuel
 
Purchased
Power(b)
 
Methane
Gas
 
Other
 
Total
Ameren:(c)
 
 
 
 
 
 
 
 
 
 
 
 
 
2016
$
664

 
$
249

 
$
51

 
$
241

 
$
3

 
$
115

 
$
1,323

2017
685

 
190

 
46

 
147

 
4

 
73

 
1,145

2018
204

 
127

 
68

 
72

 
5

 
55

 
531

2019
110

 
89

 
24

 
58

 
5

 
56

 
342

2020
—

 
43

 
51

 
58

 
6

 
57

 
215

Thereafter
—

 
60

 
108

 
539

 
71

 
350

 
1,128

Total
$
1,663

 
$
758

 
$
348

 
$
1,115

 
$
94

 
$
706

 
$
4,684

Ameren Missouri:
 
 
 
 
 
 
 
 
 
 
 
 
 
2016
$
664

 
$
46

 
$
51

 
$
23

 
$
3

 
$
46

 
$
833

2017
685

 
36

 
46

 
23

 
4

 
32

 
826

2018
204

 
24

 
68

 
23

 
5

 
28

 
352

2019
110

 
14

 
24

 
23

 
5

 
29

 
205

2020
—

 
10

 
51

 
23

 
6

 
30

 
120

Thereafter
—

 
23

 
108

 
84

 
71

 
183

 
469

Total
$
1,663

 
$
153

 
$
348

 
$
199

 
$
94

 
$
348

 
$
2,805

Ameren Illinois:
 
 
 
 
 
 
 
 
 
 
 
 
 
2016
$
—

 
$
203

 
$
—

 
$
218

 
$
—

 
$
31

 
$
452

2017
—

 
154

 
—

 
124

 
—

 
25

 
303

2018
—

 
103

 
—

 
49

 
—

 
24

 
176

2019
—

 
75

 
—

 
35

 
—

 
27

 
137

2020
—

 
33

 
—

 
35

 
—

 
27

 
95

Thereafter
—

 
37

 
—

 
455

 
—

 
167

 
659

Total
$
—

 
$
605

 
$
—

 
$
916

 
$
—

 
$
301

 
$
1,822

(a)
Includes amounts for generation and for distribution.
(b)
The purchased power amounts for Ameren and Ameren Illinois include agreements through 2032 for renewable energy credits with various renewable energy suppliers. The agreements contain a provision that allows Ameren Illinois to reduce the quantity purchased in the event that Ameren Illinois would not be able to recover the costs associated with the renewable energy credits.
(c)
Includes amounts for Ameren registrant and nonregistrant subsidiaries.
Schedule Of Asbestos-Related Litigation Pending Lawsuits 
he following table presents the pending asbestos-related lawsuits filed against Ameren Missouri and Ameren Illinois as of December 31, 2015:
Ameren
Missouri
 
Ameren
Illinois
 
Total(a)
26
 
38
 
48

(a)
Total does not equal the sum of the subsidiary unit lawsuits because some of the lawsuits name multiple Ameren entities as defendants.
Divestiture Transactions and Discontinued Operations (Tables)
Schedule of Disposal Groups, Including Discontinued Operations, Income Statement, Balance Sheet and Additional Disclosures
The following table presents the components of discontinued operations in Ameren's consolidated statement of income (loss) for the years ended December 31, 2015, 2014, and 2013:
 
Year ended
 
 
2015
 
2014
 
2013
 
Operating revenues
$
—

 
$
1

 
$
1,037

 
Operating benefits (expenses)
1


(2
)
 
(1,207
)
(a) 
Operating income (loss)
1

 
(1
)
 
(170
)
 
Other income (loss)
—

 
—

 
(1
)
 
Interest charges
—

 
—

 
(39
)
 
Income (loss) before income taxes
1

 
(1
)
 
(210
)
 
Income tax (expense) benefit
50

 
—

 
(13
)
 
Income (loss) from discontinued operations, net of taxes
$
51

 
$
(1
)
 
$
(223
)
 
(a)
Includes a $201 million pretax loss on disposal relating to the New AER divestiture.
The following table presents the carrying amounts of the components of assets and liabilities of Ameren's discontinued operations, which consist primarily of AROs and related deferred income tax assets associated with the abandoned Meredosia and Hutsonville energy centers, at December 31, 2015 and 2014:
 
December 31, 2015
 
December 31, 2014
Assets of discontinued operations
 
 
 
Accumulated deferred income taxes, net
$
14

 
$
15

Total assets of discontinued operations
$
14

 
$
15

Liabilities of discontinued operations
 
 
 
Accounts payable and other current obligations
$
1

 
$
1

Asset retirement obligations(a)
28

 
32

Total liabilities of discontinued operations
$
29

 
$
33


(a)
Ameren is demolishing the Hutsonville energy center and expects to demolish the Meredosia energy center beginning in 2016.
Segment Information (Tables)
Schedule Of Segment Reporting Information, By Segment
The following table presents information about the reported revenues and specified items reflected in Ameren’s net income attributable to Ameren common shareholders and capital expenditures from continuing operations for the years ended December 31, 2015, 2014, and 2013, and total assets in continuing operations as of December 31, 2015, 2014, and 2013:
 
Ameren
Missouri
 
Ameren
Illinois
 
Other
 
Intersegment
Eliminations
 
Consolidated
 
2015
 
 
 
 
 
 
 
 
 
 
External revenues
$
3,566

 
$
2,462

 
$
70

 
$
—

 
$
6,098

 
Intersegment revenues
43

 
4

 
2

 
(49
)
 
—

 
Depreciation and amortization
492

 
295

 
9

 
—

 
796

 
Interest and dividend income
28

 
12

 
1

 
—

 
41

 
Interest charges
219

 
131

 
5

 
—

 
355

 
Income taxes
209

 
127

 
27

 
—

 
363

 
Net income attributable to Ameren common shareholders from continuing operations
352

 
214

 
13

 
—

 
579

 
Capital expenditures
622

 
918

 
377

(a) 
—

 
1,917

 
Total assets(c)
13,851

 
8,903

 
1,139

 
(267
)
 
23,626

(b) 
2014
 
 
 
 
 
 
 
 
 
 
External revenues
$
3,526

 
$
2,496

 
$
31

 
$
—

 
$
6,053

 
Intersegment revenues
27

 
2

 
2

 
(31
)
 
—

 
Depreciation and amortization
473

 
263

 
9

 
—

 
745

 
Interest and dividend income
28

 
7

 
2

 
—

 
37

 
Interest charges
211

 
112

 
18

 
—

 
341

 
Income taxes
229

 
143

 
5

 
—

 
377

 
Net income (loss) attributable to Ameren common shareholders from continuing operations
390

 
201

 
(4
)
 
—

 
587

 
Capital expenditures
747

 
835

 
203

(a) 
—

 
1,785

 
Total assets(c)
13,474

 
8,204

 
799

 
(203
)
 
22,274

(b) 
2013
 
 
 
 
 
 
 
 
 
 
External revenues
$
3,516

 
$
2,307

 
$
15

 
$
—

 
$
5,838

 
Intersegment revenues
25

 
4

 
2

 
(31
)
 
—

 
Depreciation and amortization
454

 
243

 
9

 
—

 
706

 
Interest and dividend income
27

 
2

 
1

 
—

 
30

 
Interest charges
210

 
143

 
45

 
—

 
398

 
Income taxes (benefit)
242

 
110

 
(41
)
 
—

 
311

 
Net income (loss) attributable to Ameren common shareholders from continuing operations
395

 
160

 
(43
)
 
—

 
512

 
Capital expenditures
648

 
701

 
30

(a) 
—

 
1,379

 
Total assets(c)
12,867

 
7,397

 
711

 
(233
)
 
20,742

(b) 

(a)
Includes the elimination of intercompany transfers.
(b)
Excludes total assets from discontinued operations of $14 million, $15 million, and $165 million as of December 31, 2015, 2014, and 2013, respectively.
(c)
Reflects the adoption of the new authoritative accounting guidance for the presentation of debt issuance costs and balance sheet classification of deferred income taxes. See Note 1 – Summary of Significant Accounting Policies for additional information.

Selected Quarterly Information (Tables)
Summary Of Selected Quarterly Information
SELECTED QUARTERLY INFORMATION (Unaudited) (In millions, except per share amounts)
Ameren
2015
 
 
2014
Quarter ended(a)
March 31
 
June 30
 
September 30
 
December 31
 
 
March 31
 
June 30
 
September 30
 
December 31
Operating revenues
$
1,556

 
$
1,401

 
$
1,833

 
$
1,308

 
 
$
1,594

 
$
1,419

 
$
1,670

 
$
1,370

Operating income
256

 
237

 
626

 
140

 
 
246

 
322

 
561

 
125

Net income
110

 
151

 
345

 
30

 
 
98

 
150

 
295

 
49

Net income attributable to Ameren common shareholders – continuing operations
$
108

 
$
98

 
$
343

 
$
30

 
 
$
97

 
$
150

 
$
294

 
$
46

Net income (loss) attributable to Ameren common shareholders – discontinued operations
—

 
52

 
—

 
(1
)
 
 
(1
)
 
(1
)
 
(1
)
 
2

Net income attributable to Ameren common shareholders
$
108

 
$
150

 
$
343

 
$
29

 
 
$
96

 
$
149

 
$
293

 
$
48

Earnings per common share – basic – continuing operations
$
0.45

 
$
0.40

 
$
1.42

 
$
0.12

 
 
$
0.40

 
$
0.62

 
$
1.21

 
$
0.19

Earnings (loss) per common share – basic – discontinued operations
—

 
0.21

 
—

 
—

 
 
—

 
(0.01
)
 
—

 
0.01

Earnings per common share – basic
$
0.45

 
$
0.61

 
$
1.42

 
$
0.12

 
 
$
0.40

 
$
0.61

 
$
1.21

 
$
0.20

Earnings per common share – diluted – continuing operations
$
0.45

 
$
0.40

 
$
1.41

 
$
0.12

 
 
$
0.40

 
$
0.62

 
$
1.20

 
$
0.19

Earnings (loss) per common share – diluted – discontinued operations
—

 
0.21

 
—

 
—

 
 
—

 
(0.01
)
 
—

 
0.01

Earnings per common share – diluted
$
0.45

 
$
0.61

 
$
1.41

 
$
0.12

 
 
$
0.40

 
$
0.61

 
$
1.20

 
$
0.20

(a)
The sum of quarterly amounts, including per share amounts, may not equal amounts reported for year-to-date periods. This is because of the effects of rounding and the changes in the number of weighted-average diluted shares outstanding each period.
Ameren Missouri Quarter ended
 
Operating
Revenues
 
Operating
Income
 
Net Income
 (Loss)
 
Net Income (Loss)
Available
to Common
Shareholder
March 31, 2015
 
$
800

 
$
115

 
$
42

 
$
41

March 31, 2014
 
817

 
119

 
48

 
47

June 30, 2015
 
884

 
146

 
62

 
61

June 30, 2014
 
900

 
243

 
127

 
126

September 30, 2015
 
1,171

 
423

 
240

 
239

September 30, 2014
 
1,097

 
394

 
223

 
222

December 31, 2015
 
754

 
58

 
11

 
11

December 31, 2014
 
739

 
29

 
(5
)
 
(5
)

Ameren Illinois Quarter ended
 
Operating
Revenues
 
Operating
Income
 
Net Income
 
Net Income
Available
to Common
Shareholder
March 31, 2015
 
$
745

 
$
120

 
$
54

 
$
53

March 31, 2014
 
774

 
120

 
54

 
53

June 30, 2015
 
513

 
83

 
32

 
31

June 30, 2014
 
519

 
75

 
29

 
28

September 30, 2015
 
655

 
189

 
98

 
98

September 30, 2014
 
572

 
158

 
75

 
75

December 31, 2015
 
553

 
74

 
33

 
32

December 31, 2014
 
633

 
97

 
46

 
45

Summary Of Significant Accounting Policies (Narrative) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Accounting Policies [Line Items]
 
 
 
Assumed Settlement of Performance Share Units
1.0 
1.8 
1.9 
Average performance share units excluded from calculation
0 
0 
0 
Goodwill
$ 411 
$ 411 
 
Deferred Income Taxes and Other Assets, Current
 
352 
 
Ameren Illinois Company
 
 
 
Accounting Policies [Line Items]
 
 
 
Unamortized Debt Issuance Expense
(18)1
(17)1
 
Capital contribution from parent
25 
15 
 
Goodwill
411 
411 
 
Public Utilities, Area Serviced
40,000 
 
 
Public Utilities, Estimated Population of Service Territory
3,100,000 
 
 
Deferred Income Taxes and Other Assets, Current
 
160 
 
Union Electric Company
 
 
 
Accounting Policies [Line Items]
 
 
 
Unamortized Debt Issuance Expense
(19)1
(18)1
 
Capital contribution from parent
224 
215 
4 
Noncash Or Part Noncash Capital Contribution From Parent
38 
9 
0 
Public Utilities, Area Serviced
24,000 
 
 
Public Utilities, Estimated Population of Service Territory
2,800,000 
 
 
Return of capital to parent
0 
(215)
 
Deferred Income Taxes and Other Assets, Current
 
49 
 
Minimum
 
 
 
Accounting Policies [Line Items]
 
 
 
Percent of average depreciable cost
3.00% 
3.00% 
3.00% 
Maximum
 
 
 
Accounting Policies [Line Items]
 
 
 
Percent of average depreciable cost
4.00% 
4.00% 
4.00% 
Power |
Ameren Illinois Company
 
 
 
Accounting Policies [Line Items]
 
 
 
Public Utilities, Number of Customers
1,200,000 
 
 
Power |
Union Electric Company
 
 
 
Accounting Policies [Line Items]
 
 
 
Public Utilities, Number of Customers
1,200,000 
 
 
Natural Gas |
Ameren Illinois Company
 
 
 
Accounting Policies [Line Items]
 
 
 
Public Utilities, Number of Customers
800,000 
 
 
Natural Gas |
Union Electric Company
 
 
 
Accounting Policies [Line Items]
 
 
 
Public Utilities, Number of Customers
100,000 
 
 
FAC |
Union Electric Company
 
 
 
Accounting Policies [Line Items]
 
 
 
Sharing Level For Fac
95.00% 
 
 
New Accounting Pronouncement, Early Adoption, Effect [Member]
 
 
 
Accounting Policies [Line Items]
 
 
 
Unamortized Debt Issuance Expense
43 
35 
 
New Accounting Pronouncement, Early Adoption, Effect [Member] |
Ameren Illinois Company
 
 
 
Accounting Policies [Line Items]
 
 
 
Unamortized Debt Issuance Expense
18 
17 
 
New Accounting Pronouncement, Early Adoption, Effect [Member] |
Union Electric Company
 
 
 
Accounting Policies [Line Items]
 
 
 
Unamortized Debt Issuance Expense
$ 19 
$ 18 
 
Summary Of Significant Accounting Policies (Schedule Of Material And Supplies) (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2015
Dec. 31, 2014
Accounting Policies [Line Items]
 
 
Fuel
$ 173 1
$ 134 1
Gas stored underground
97 
127 
Other materials and supplies
268 
263 
Total materials and supplies
538 
524 
Union Electric Company
 
 
Accounting Policies [Line Items]
 
 
Fuel
173 1
134 1
Gas stored underground
10 
16 
Other materials and supplies
204 
197 
Total materials and supplies
387 
347 
Ameren Illinois Company
 
 
Accounting Policies [Line Items]
 
 
Fuel
0 1
0 1
Gas stored underground
87 
111 
Other materials and supplies
64 
66 
Total materials and supplies
$ 151 
$ 177 
Summary Of Significant Accounting Policies (Schedule Of Rates Used For Allowance For Funds Used During Construction) (Details)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Union Electric Company
 
 
 
Accounting Policies [Line Items]
 
 
 
Allowance for funds used during construction, rate
7.00% 
7.00% 
8.00% 
Ameren Illinois Company
 
 
 
Accounting Policies [Line Items]
 
 
 
Allowance for funds used during construction, rate
6.00% 
2.00% 
8.00% 
Summary Of Significant Accounting Policies (Schedule Of Asset Retirement Obligations) (Details) (USD $)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
 
 
Balance
$ 396,000,000 
$ 369,000,000 
Liabilities incurred
3,000,000 
2,000,000 
Liabilities settled
(2,000,000)
(2,000,000)
Accretion in period
23,000,000 1
21,000,000 1
Change in estimates
203,000,000 2
6,000,000 3
Balance
623,000,000 4
396,000,000 
Other current liabilities
379,000,000 
434,000,000 
Union Electric Company
 
 
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
 
 
Balance
389,000,000 
366,000,000 
Liabilities incurred
3,000,000 
2,000,000 
Liabilities settled
(1,000,000)
(2,000,000)
Accretion in period
23,000,000 1
21,000,000 1
Change in estimates
203,000,000 2
2,000,000 3
Balance
617,000,000 4
389,000,000 
Other current liabilities
120,000,000 
117,000,000 
Ameren Illinois Company
 
 
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
 
 
Balance
7,000,000 5
3,000,000 
Liabilities incurred
0 
0 
Liabilities settled
(1,000,000)
(1,000,000)6
Accretion in period
1,000,000 1 6
1,000,000 1 6
Change in estimates
1,000,000 2 6
4,000,000 3
Balance
6,000,000 5
7,000,000 5
Other current liabilities
114,000,000 
124,000,000 
Callaway energy center decommissioning study [Member]
 
 
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
 
 
Change in estimates
99,000,000 
 
New CCR Rules Estimate [Member]
 
 
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
 
 
Change in estimates
100,000,000 
 
Other Estimate Changes [Member]
 
 
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
 
 
Change in estimates
4,000,000 
 
Asset Retirement Obligation Balance [Member]
 
 
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
 
 
Other current liabilities
$ 5,000,000 
 
[2] The ARO increase resulted in a corresponding increase recorded to "Property and Plant, Net." Ameren and Ameren Missouri increased their AROs related to the decommissioning of the Callaway energy center by $99 million to reflect the 2015 cost study and funding analysis filed with the MoPSC, the extension of the estimated operating life until 2044, and a reduction in the discount rate assumption. See Note 10 – Callaway Energy Center for additional information. In addition, as a result of new federal regulations, Ameren and Ameren Missouri recorded an increase of $100 million to their AROs associated with CCR storage facilities. See Note 15 – Commitments and Contingencies for additional information. Ameren and Ameren Missouri also increased their AROs by $4 million due to a change in the estimated retirement dates of the Meramec and Rush Island energy centers as a result of the MoPSC's April 2015 electric rate order.
Summary Of Significant Accounting Policies (Schedule Of Excise Taxes) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Accounting Policies [Line Items]
 
 
 
Excise tax expense
$ 213 
$ 215 
$ 213 
Union Electric Company
 
 
 
Accounting Policies [Line Items]
 
 
 
Excise tax expense
156 
151 
152 
Ameren Illinois Company
 
 
 
Accounting Policies [Line Items]
 
 
 
Excise tax expense
$ 57 
$ 64 
$ 61 
Summary Of Significant Accounting Policies (Basic and Diluted Earnings Per Share Calculations) (Details)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Accounting Policies [Abstract]
 
 
 
Assumed Settlement of Performance Share Units
1.0 
1.8 
1.9 
Average performance share units excluded from calculation
0 
0 
0 
Summary Of Significant Accounting Policies Summary of Significant Accounting Policies (Supplemental Cash Flow Information) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Supplemental Cash Flow Information [Line Items]
 
 
 
Interest Paid, Capitalized
$ 17 
$ 18 
$ 37 
Interest Paid, Net
335 
333 
393 
Income Taxes Paid, Net
(15)
(27)
8 
Continuing Operations
 
 
 
Supplemental Cash Flow Information [Line Items]
 
 
 
Interest Paid, Capitalized
17 
18 
20 
Interest Paid, Net
335 1
333 1
362 1
Income Taxes Paid, Net
(17)
(41)
116 
Discontinued Operations
 
 
 
Supplemental Cash Flow Information [Line Items]
 
 
 
Interest Paid, Capitalized
0 
0 
17 
Interest Paid, Net
0 2
0 2
31 2
Income Taxes Paid, Net
$ 2 
$ 14 
$ (108)
Rate And Regulatory Matters Rate and Regulatory Matters (Narrative-Missouri) (Details) (USD $)
1 Months Ended 12 Months Ended 36 Months Ended 36 Months Ended 12 Months Ended 3 Months Ended
Apr. 30, 2015
Electric Distribution
Final Rate Order
Union Electric Company
Apr. 30, 2015
Electric Distribution - Net Energy Costs [Member]
Final Rate Order
Union Electric Company
Dec. 31, 2015
Illinois Rivers Project [Member]
Ameren Transmission Company of Illinois [Member]
mi
Dec. 31, 2015
Mark Twain Project [Member]
Ameren Transmission Company of Illinois [Member]
mi
Dec. 31, 2015
MEEIA
Electric Distribution
Union Electric Company
Dec. 31, 2012
MEEIA
Electric Distribution
Union Electric Company
Feb. 28, 2019
Subsequent Event
MEEIA
Electric Distribution
Union Electric Company
Mar. 31, 2016
Subsequent Event
MEEIA
Electric Distribution
Union Electric Company
Mar. 31, 2016
Subsequent Event
Minimum
MEEIA
Electric Distribution
Union Electric Company
Dec. 31, 2015
Noranda [Member]
Union Electric Company
MWh
Mar. 31, 2016
Noranda [Member]
Subsequent Event
Union Electric Company
Rate And Regulatory Matters [Line Items]
 
 
 
 
 
 
 
 
 
 
 
Public Utilities, Approved Rate Increase (Decrease), Amount
$ 122,000,000 
$ 109,000,000 
 
 
 
 
 
 
 
 
 
Public Utilities, Approved Return on Equity, Percentage
9.53% 
 
 
 
 
 
 
 
 
 
 
Public Utilities, Approved Equity Capital Structure, Percentage
51.80% 
 
 
 
 
 
 
 
 
 
 
Rate Base
7,000,000,000 
 
 
 
 
 
 
 
 
 
 
Energy Efficiency Program Spending
 
 
 
 
134,000,000 
 
158,000,000 
 
 
 
 
Net Shared Benefits
 
 
 
 
174,000,000 
 
 
 
 
 
 
Incentive Award if Energy Efficiency Goals Are Achieved
 
 
 
 
19,000,000 
 
27,000,000 
 
 
 
 
Achieved Percentage of Energy Efficiency Earnings For Incentive Award
 
 
 
 
100.00% 
100.00% 
 
100.00% 
25.00% 
 
 
Incentive Award if Energy Efficiency Goals Are Achieved, Period of Recognition
 
 
 
 
3 years 
 
3 years 
 
 
 
 
Incentive Award if Energy Efficiency Goals Are Achieved, Period
 
 
 
 
 
 
3 years 
 
 
 
 
Customer pot lines Idled due to circuit failure
 
 
 
 
 
 
 
 
 
 
2 
Number of customer pot lines
 
 
 
 
 
 
 
 
 
 
3 
Revenue Requirement
 
 
 
 
 
 
 
 
 
78,000,000 
 
Noranda Annual Megawatthours
 
 
 
 
 
 
 
 
 
4,200,000.0 
 
Noranda Operating Capacity
 
 
 
 
 
 
 
 
 
100.00% 
 
Noranda Summer Base Rate
 
 
 
 
 
 
 
 
 
45.78 
 
Noranda Winter Base Rate
 
 
 
 
 
 
 
 
 
$ 31.11 
 
Number of days to file a rate case
 
 
 
 
 
 
 
 
 
 
60 days 
Number of Months to complete MoPSC Electric Service Proceeding
 
 
 
 
 
 
 
 
 
 
11 months 
Transmission Line Miles
 
 
7 
100 
 
 
 
 
 
 
 
Rate And Regulatory Matters (Narrative-Illinois) (Details) (USD $)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2015
Ameren Illinois Company
Dec. 31, 2014
Ameren Illinois Company
Dec. 31, 2015
Ameren Illinois Company
2015 IEMA Revenue Requirement Reconciliation [Member]
IEIMA
Electric Distribution
Dec. 31, 2015
Ameren Illinois Company
2014 IEMA Revenue Requirement Reconciliation [Member]
IEIMA
Electric Distribution
Dec. 31, 2014
Ameren Illinois Company
2013 IEMA Revenue Requirement Reconciliation [Member]
IEIMA
Electric Distribution
Dec. 31, 2015
Ameren Illinois Company
Final Rate Order
Gas Distribution
Dec. 31, 2015
Ameren Illinois Company
Final Rate Order
Electric Distribution
Dec. 31, 2015
Ameren Illinois Company
Final Rate Order
IEIMA
Electric Distribution
Dec. 31, 2015
Ameren Transmission Company of Illinois [Member]
Spoon River Project [Member]
mi
Rate And Regulatory Matters [Line Items]
 
 
 
 
 
 
 
 
 
 
 
Regulatory assets
$ 1,382,000,000 
$ 1,582,000,000 
$ 771,000,000 
$ 883,000,000 
$ 62,000,000 
 
 
 
 
 
 
Current regulatory assets
260,000,000 
295,000,000 
167,000,000 
129,000,000 
 
103,000,000 
65,000,000 
 
 
 
 
Public Utilities, Approved Rate Increase (Decrease), Amount
 
 
 
 
 
 
 
45,000,000 
15,000,000 
106,000,000 
 
Disallowed costs associated with debt redemption
 
 
 
 
 
 
 
 
15,000,000 
 
 
Allowed Costs Associated with Debt Redemption
 
 
 
 
 
 
 
 
11,000,000 
 
 
Public Utilities, Approved Return on Equity, Percentage
 
 
 
 
 
 
 
9.60% 
 
 
 
Public Utilities, Approved Equity Capital Structure, Percentage
 
 
 
 
 
 
 
50.00% 
 
 
 
Rate base
 
 
 
 
 
 
 
$ 1,200,000,000 
 
 
 
Transmission Line Miles
 
 
 
 
 
 
 
 
 
 
46 
Rate And Regulatory Matters Rate and Regulatory Matters (Narrative-Federal) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended 12 Months Ended 1 Months Ended 12 Months Ended 12 Months Ended
Dec. 31, 2015
Dec. 31, 2013
Dec. 31, 2014
Dec. 31, 2015
Midwest Independent Transmission System Operator, Inc [Member]
Administrative Law Judge [Member]
Feb. 28, 2015
Midwest Independent Transmission System Operator, Inc [Member]
Pending Ferc Case [Member]
Dec. 31, 2015
Midwest Independent Transmission System Operator, Inc [Member]
Pending Ferc Case [Member]
Dec. 31, 2015
Ameren Illinois Company
Dec. 31, 2014
Ameren Illinois Company
Dec. 31, 2015
Ameren Illinois Company
Midwest Independent Transmission System Operator, Inc [Member]
Pending Ferc Case [Member]
Dec. 31, 2015
Union Electric Company
Dec. 31, 2014
Union Electric Company
Dec. 31, 2013
Union Electric Company
Dec. 31, 2015
New Nuclear Energy Center COL [Member]
Dec. 31, 2015
New Nuclear Energy Center COL [Member]
Union Electric Company
Dec. 31, 2015
Final Rate Order
Ameren Illinois Company
Rate And Regulatory Matters [Line Items]
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Payments for Legal Settlements
 
 
 
 
 
 
 
 
 
 
 
 
 
 
$ 8 
Public Utilities, Approved Return on Equity, Percentage
 
 
 
10.32% 
 
12.38% 
 
 
 
 
 
 
 
 
 
Customer Requested Rate on Equity
 
 
 
 
8.67% 
9.15% 
 
 
 
 
 
 
 
 
 
Basis point reduction in FERC allowed base return on common equity
 
 
 
 
 
0.50% 
 
 
 
 
 
 
 
 
 
Current regulatory liabilities
80 
 
106 
 
 
45 
39 
84 
32 
28 
18 
 
 
 
 
Investments in Power and Distribution Projects
 
 
 
 
 
 
 
 
 
 
 
 
 
69 
 
Provision for Callaway construction and operating license
$ 69 
$ 0 
 
 
 
 
 
 
 
$ 69 
$ 0 
$ 0 
$ 69 
$ 69 
 
Rate And Regulatory Matters (Schedule Of Regulatory Assets And Liabilities) (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2015
Dec. 31, 2014
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory assets
$ 260 
$ 295 
Regulatory assets
1,382 
1,582 
Current regulatory liabilities
80 
106 
Regulatory liabilities
1,905 
1,850 
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory assets
89 
163 
Regulatory assets
605 
695 
Current regulatory liabilities
28 
18 
Regulatory liabilities
1,172 
1,147 
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory assets
167 
129 
Regulatory assets
771 
883 
Current regulatory liabilities
39 
84 
Regulatory liabilities
732 
703 
Under-Recovered FAC
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory assets
37 1 2
128 1 2
Under-Recovered FAC |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory assets
37 1 2
128 1 2
Under-Recovered FAC |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory assets
0 1 2
0 1 2
Under-Recovered Illinois Electric Power Costs
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory assets
3 3
2 3
Under-Recovered Illinois Electric Power Costs |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory assets
0 3
0 3
Under-Recovered Illinois Electric Power Costs |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory assets
3 3
2 3
Under-Recovered PGA
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory assets
8 3
20 3
Under-Recovered PGA |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory assets
0 3
0 3
Under-Recovered PGA |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory assets
8 3
20 3
MTM Derivative Losses
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory assets
74 4
74 4
Regulatory assets
190 4
158 4
MTM Derivative Losses |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory assets
29 4
32 4
Regulatory assets
15 4
14 4
MTM Derivative Losses |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory assets
45 4
42 4
Regulatory assets
175 4
144 4
Energy Efficiency Rider
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory assets
23 5
3 5
Regulatory liabilities
36 5
39 5
Energy Efficiency Rider |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory assets
23 5
3 5
Regulatory liabilities
0 5
0 5
Energy Efficiency Rider |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory assets
0 5
0 5
Regulatory liabilities
36 5
39 5
IEIMA
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory assets
103 1 6
65 1 6
Regulatory assets
62 1 6
101 1 6
IEIMA |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory assets
0 1 6
0 1 6
Regulatory assets
0 1 6
0 1 6
IEIMA |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory assets
103 1 6
65 1 6
Regulatory assets
62 1 6
101 1 6
FERC Revenue Requirement Reconciliation
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory assets
12 1 7
3 1 7
Regulatory assets
11 1 7
12 1 7
Current regulatory liabilities
0 7
11 7
FERC Revenue Requirement Reconciliation |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory assets
0 1 7
0 1 7
Regulatory assets
0 1 7
0 1 7
Current regulatory liabilities
0 7
0 7
FERC Revenue Requirement Reconciliation |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory assets
8 1 7
0 1 7
Regulatory assets
5 1 7
8 1 7
Current regulatory liabilities
0 7
11 7
Pension And Postretirement Benefit Costs
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
297 8
423 8
Pension And Postretirement Benefit Costs |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
95 8
148 8
Pension And Postretirement Benefit Costs |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
202 8
275 8
Income Taxes
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
258 9
256 9
Regulatory liabilities
42 10
55 10
Income Taxes |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
254 9
253 9
Regulatory liabilities
36 10
41 10
Income Taxes |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
4 9
3 9
Regulatory liabilities
6 10
14 10
Asset Retirement Obligation
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
4 11
5 11
Regulatory liabilities
167 11
182 11
Asset Retirement Obligation |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
0 11
0 11
Regulatory liabilities
167 11
182 11
Asset Retirement Obligation |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
4 11
5 11
Regulatory liabilities
0 11
0 11
Callaway Costs
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
32 1 12
36 1 12
Callaway Costs |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
32 1 12
36 1 12
Callaway Costs |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
0 1 12
0 1 12
Unamortized Loss On Reacquired Debt
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
138 1 13
152 1 13
Unamortized Loss On Reacquired Debt |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
69 1 13
72 1 13
Unamortized Loss On Reacquired Debt |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
69 1 13
80 1 13
Recoverable Costs Contaminated Facilities
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
230 14
251 14
Recoverable Costs Contaminated Facilities |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
0 14
0 14
Recoverable Costs Contaminated Facilities |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
230 14
251 14
Storm Costs
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
9 1 15
3 1 15
Storm Costs |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
0 1 15
0 1 15
Storm Costs |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
9 1 15
3 1 15
Demand-Side Costs
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
31 1 16
44 1 16
Demand-Side Costs |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
31 1 16
44 1 16
Demand-Side Costs |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
0 1 16
0 1 16
Reserve For Workers' Compensation Liabilities
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
13 17
14 17
Reserve For Workers' Compensation Liabilities |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
6 17
7 17
Reserve For Workers' Compensation Liabilities |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
7 17
7 17
Credit Facilities Fees
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
4 18
5 18
Credit Facilities Fees |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
4 18
5 18
Credit Facilities Fees |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
0 18
0 18
Construction Accounting For Pollution Control Equipment
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
20 1 19
21 1 19
Construction Accounting For Pollution Control Equipment |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
20 1 19
21 1 19
Construction Accounting For Pollution Control Equipment |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
0 1 19
0 1 19
Solar Rebates
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
74 1 20
88 1 20
Solar Rebates |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
74 1 20
88 1 20
Solar Rebates |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
0 1 20
0 1 20
Other
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
9 
13 
Regulatory liabilities
3 
0 
Other |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
5 
7 
Regulatory liabilities
2 
0 
Other |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory assets
4 
6 
Regulatory liabilities
1 
0 
Over-Recovered FAC
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory liabilities
9 2
0 2
Over-Recovered FAC |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory liabilities
9 2
0 2
Over-Recovered FAC |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory liabilities
0 2
0 2
Over-Recovered Illinois Electric Power Costs
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory liabilities
6 3
26 3
Over-Recovered Illinois Electric Power Costs |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory liabilities
0 3
0 3
Over-Recovered Illinois Electric Power Costs |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory liabilities
6 3
26 3
Over-Recovered PGA
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory liabilities
3 3
27 3
Over-Recovered PGA |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory liabilities
3 3
2 3
Over-Recovered PGA |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory liabilities
0 3
25 3
MTM Derivative Gains
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory liabilities
17 4
17 4
MTM Derivative Gains |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory liabilities
16 4
16 4
MTM Derivative Gains |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory liabilities
1 4
1 4
Refund Reserves for FERC Orders and Audit Findings
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory liabilities
45 21
25 21
Refund Reserves for FERC Orders and Audit Findings |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory liabilities
0 21
0 21
Refund Reserves for FERC Orders and Audit Findings |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Current regulatory liabilities
32 21
21 21
Uncertain tax positions tracker
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory liabilities
6 22
7 22
Uncertain tax positions tracker |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory liabilities
6 22
7 22
Uncertain tax positions tracker |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory liabilities
0 22
0 22
Removal Costs
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory liabilities
1,605 23
1,529 23
Removal Costs |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory liabilities
933 23
886 23
Removal Costs |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory liabilities
671 23
643 23
Bad Debt Rider
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory liabilities
6 24
7 24
Bad Debt Rider |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory liabilities
0 24
0 24
Bad Debt Rider |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory liabilities
6 24
7 24
Pension And Postretirement Benefit Costs Tracker
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory liabilities
19 25
24 25
Pension And Postretirement Benefit Costs Tracker |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory liabilities
19 25
24 25
Pension And Postretirement Benefit Costs Tracker |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory liabilities
0 25
0 25
Renewable Energy Credits
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory liabilities
12 26
1 26
Renewable Energy Credits |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory liabilities
0 26
1 26
Renewable Energy Credits |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory liabilities
12 26
0 26
Storm Tracker
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory liabilities
9 27
6 27
Storm Tracker |
Union Electric Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory liabilities
9 27
6 27
Storm Tracker |
Ameren Illinois Company
 
 
Rate And Regulatory Matters [Line Items]
 
 
Regulatory liabilities
$ 0 27
$ 0 27
[5] (e)The Ameren Missouri balance relates to the MEEIA. Beginning in January 2014, the MEEIA rider allowed Ameren Missouri to collect from or refund to customers any annual difference in the actual amounts incurred and the amounts collected from customers for the MEEIA program costs and its net shared benefits. Under the MEEIA rider, collections from or refunds to customers occur one year after the program costs and lost revenues are incurred. The Ameren Illinois balance relates to a regulatory tracking mechanism to recover its electric and natural gas costs associated with developing, implementing, and evaluating customer energy efficiency and demand response programs. Any under-recovery or over-recovery will be collected from or refunded to customers over the 12 months following the plan year.
Property And Plant, Net (Schedule Of Property And Plant, Net) (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2015
equipment
Dec. 31, 2014
Property, Plant and Equipment [Line Items]
 
 
Property and plant, at original cost
$ 27,603 1
$ 26,198 1
Accumulated depreciation and amortization
10,347 1
9,759 1
Property and plant, before construction work in progress
17,256 1
16,439 1
Property, Plant and Equipment, Net
18,799 1
17,424 1
Number of combustion turbine electric generation equipment under capital lease agreements
2 
 
Number of capital lease agreements
2 
 
Capital lease agreements, gross asset value
233 
 
Total accumulated depreciation, capital lease agreements
72 
66 
Held-to-maturity Securities
288 
294 
Electric
 
 
Property, Plant and Equipment [Line Items]
 
 
Property and plant, at original cost
25,161 1
23,913 1
Gas
 
 
Property, Plant and Equipment [Line Items]
 
 
Property and plant, at original cost
2,442 1
2,285 1
Nuclear Fuel
 
 
Property, Plant and Equipment [Line Items]
 
 
Construction work in progress
275 1
209 1
Other Energy
 
 
Property, Plant and Equipment [Line Items]
 
 
Construction work in progress
1,268 1
776 1
Union Electric Company
 
 
Property, Plant and Equipment [Line Items]
 
 
Property and plant, at original cost
17,966 1
17,483 1
Accumulated depreciation and amortization
7,460 1
7,086 1
Property and plant, before construction work in progress
10,506 1
10,397 1
Property, Plant and Equipment, Net
11,183 1
10,867 1
Union Electric Company |
Electric
 
 
Property, Plant and Equipment [Line Items]
 
 
Property and plant, at original cost
17,521 1
17,052 1
Union Electric Company |
Gas
 
 
Property, Plant and Equipment [Line Items]
 
 
Property and plant, at original cost
445 1
431 1
Union Electric Company |
Nuclear Fuel
 
 
Property, Plant and Equipment [Line Items]
 
 
Construction work in progress
275 1
209 1
Union Electric Company |
Other Energy
 
 
Property, Plant and Equipment [Line Items]
 
 
Construction work in progress
402 1
261 1
Ameren Illinois Company
 
 
Property, Plant and Equipment [Line Items]
 
 
Property and plant, at original cost
9,250 
8,371 
Accumulated depreciation and amortization
2,632 
2,422 
Property and plant, before construction work in progress
6,618 
5,949 
Property, Plant and Equipment, Net
6,848 
6,165 
Ameren Illinois Company |
Electric
 
 
Property, Plant and Equipment [Line Items]
 
 
Property and plant, at original cost
7,253 
6,517 
Ameren Illinois Company |
Gas
 
 
Property, Plant and Equipment [Line Items]
 
 
Property and plant, at original cost
1,997 
1,854 
Ameren Illinois Company |
Nuclear Fuel
 
 
Property, Plant and Equipment [Line Items]
 
 
Construction work in progress
0 
0 
Ameren Illinois Company |
Other Energy
 
 
Property, Plant and Equipment [Line Items]
 
 
Construction work in progress
230 
216 
Other
 
 
Property, Plant and Equipment [Line Items]
 
 
Property and plant, at original cost
387 
344 
Accumulated depreciation and amortization
255 
251 
Property and plant, before construction work in progress
132 
93 
Property, Plant and Equipment, Net
768 
392 
Other |
Electric
 
 
Property, Plant and Equipment [Line Items]
 
 
Property and plant, at original cost
387 
344 
Other |
Gas
 
 
Property, Plant and Equipment [Line Items]
 
 
Property and plant, at original cost
0 
0 
Other |
Nuclear Fuel
 
 
Property, Plant and Equipment [Line Items]
 
 
Construction work in progress
0 
0 
Other |
Other Energy
 
 
Property, Plant and Equipment [Line Items]
 
 
Construction work in progress
$ 636 
$ 299 
Property And Plant, Net (Accrued Capital Expenditures) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Property, Plant and Equipment [Line Items]
 
 
 
Accrued capital expenditures
$ 235 1
$ 181 1
$ 175 1
Union Electric Company
 
 
 
Property, Plant and Equipment [Line Items]
 
 
 
Accrued capital expenditures
85 
72 
74 
Ameren Illinois Company
 
 
 
Property, Plant and Equipment [Line Items]
 
 
 
Accrued capital expenditures
92 
59 
86 
Nuclear Fuel
 
 
 
Property, Plant and Equipment [Line Items]
 
 
 
Accrued capital expenditures
16 1
13 1
8 1
Nuclear Fuel |
Union Electric Company
 
 
 
Property, Plant and Equipment [Line Items]
 
 
 
Accrued capital expenditures
$ 16 
$ 13 
$ 8 
Short-Term Debt And Liquidity (Narrative) (Details) (USD $)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Illinois Credit Agreement 2012 |
Maximum
 
 
Line of Credit Facility [Line Items]
 
 
Line of credit facility, maximum borrowing capacity
$ 1,300,000,000.0 
 
Illinois Credit Agreement 2012 |
Ameren Illinois Company
 
 
Line of Credit Facility [Line Items]
 
 
Line of credit facility, maximum borrowing capacity
800,000,000 
 
Actual debt-to-capital ratio
0.47 
 
Missouri Credit Agreement 2012 |
Maximum
 
 
Line of Credit Facility [Line Items]
 
 
Line of credit facility, maximum borrowing capacity
1,200,000,000.0 
 
Missouri Credit Agreement 2012 |
Union Electric Company
 
 
Line of Credit Facility [Line Items]
 
 
Line of credit facility, maximum borrowing capacity
800,000,000 
 
Actual debt-to-capital ratio
0.49 
 
Credit Agreements 2012
 
 
Line of Credit Facility [Line Items]
 
 
Line of credit facility, maximum borrowing capacity
1,800,000,000.0 
 
Covenant terms, default provisions, maximum indebtedness
75,000,000 
 
Multiyear Credit Facility
 
 
Line of Credit Facility [Line Items]
 
 
Line of credit facility, maximum borrowing capacity
2,100,000,000 
 
Number of lenders
24 
 
Line of credit facility, maximum borrowing capacity, per lender
115,000,000 
 
Actual debt-to-capital ratio
0.51 
 
Minimum ratio of consolidated funds from operations plus interest expense to consolidated interest expense as of balance sheet date
2.0 to 1.0 
 
Line of Credit Facility, Commitment Fee Amount
$ 100,000,000 
 
Multiyear Credit Facility |
Maximum
 
 
Line of Credit Facility [Line Items]
 
 
Actual debt-to-capital ratio
0.65 
 
Utilities
 
 
Line of Credit Facility [Line Items]
 
 
Short Term Debt, Weighted Average Interest Rate During Period
0.11% 
0.19% 
Short-Term Debt And Liquidity (Schedule Of Maximum Aggregate Amount Available On Credit Agreements) (Details) (USD $)
Dec. 31, 2015
Illinois Credit Agreement 2012 |
Parent Company
 
Line of Credit Facility [Line Items]
 
Line of credit facility, maximum borrowing capacity
$ 500,000,000 
Illinois Credit Agreement 2012 |
Ameren Illinois Company
 
Line of Credit Facility [Line Items]
 
Line of credit facility, maximum borrowing capacity
800,000,000 
Missouri Credit Agreement 2012 |
Parent Company
 
Line of Credit Facility [Line Items]
 
Line of credit facility, maximum borrowing capacity
700,000,000 
Missouri Credit Agreement 2012 |
Union Electric Company
 
Line of Credit Facility [Line Items]
 
Line of credit facility, maximum borrowing capacity
$ 800,000,000 
Short-Term Debt And Liquidity Short-Term Debt And Liquidity (Commercial Paper) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Commercial Paper
 
 
Line of Credit Facility [Line Items]
 
 
Average Daily Commercial Paper Borrowings Outstanding
$ 767 
$ 639 
Commercial paper outstanding
301 
714 
Weighted average interest rate
0.55% 
0.36% 
Peak short-term borrowings
1,108 1
910 1
Peak short-term borrowings interest rate
0.91% 
0.75% 
Parent Company
 
 
Line of Credit Facility [Line Items]
 
 
Average Daily Commercial Paper Borrowings Outstanding
721 
423 
Weighted average interest rate
0.57% 
0.36% 
Peak short-term borrowings
874 1
625 1
Peak short-term borrowings interest rate
0.91% 
0.75% 
Parent Company |
Commercial Paper
 
 
Line of Credit Facility [Line Items]
 
 
Commercial paper outstanding
301 
585 
Union Electric Company
 
 
Line of Credit Facility [Line Items]
 
 
Average Daily Commercial Paper Borrowings Outstanding
42 
110 
Weighted average interest rate
0.50% 
0.38% 
Peak short-term borrowings
294 1
495 1
Peak short-term borrowings interest rate
0.60% 
0.70% 
Ameren Illinois Company
 
 
Line of Credit Facility [Line Items]
 
 
Average Daily Commercial Paper Borrowings Outstanding
4 
165 
Weighted average interest rate
0.44% 
0.32% 
Peak short-term borrowings
48 1
300 1
Peak short-term borrowings interest rate
0.60% 
0.60% 
Ameren Illinois Company |
Commercial Paper
 
 
Line of Credit Facility [Line Items]
 
 
Commercial paper outstanding
0 
32 
Ameren Missouri [Member] |
Commercial Paper
 
 
Line of Credit Facility [Line Items]
 
 
Commercial paper outstanding
$ 0 
$ 97 
Long-Term Debt And Equity Financings (Narrative) (Details) (USD $)
12 Months Ended 1 Months Ended 12 Months Ended 12 Months Ended 3 Months Ended 3 Months Ended 1 Months Ended 3 Months Ended 3 Months Ended 1 Months Ended 3 Months Ended 1 Months Ended 1 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2015
Union Electric Company
Dec. 31, 2014
Union Electric Company
Dec. 31, 2013
Union Electric Company
Dec. 31, 2015
Ameren Illinois Company
Dec. 31, 2014
Ameren Illinois Company
Dec. 31, 2013
Ameren Illinois Company
Jan. 31, 2014
Ameren Illinois Company
Jan. 31, 2014
Ameren Illinois Company
Environmental Improvement And Pollution Control Revenue Bonds
Dec. 31, 2015
Parent Company
Dec. 31, 2014
Parent Company
Dec. 31, 2013
Parent Company
May 31, 2014
Parent Company
Oct. 31, 2013
Parent Company
Dec. 31, 2015
Ameren Missouri and Ameren Illinois
Dec. 31, 2015
Senior Unsecured Notes270 due 2020 [Member]
Parent Company
Dec. 31, 2015
Senior Unsecured Notes270 due 2020 [Member]
Parent Company
Unsecured Debt [Member]
Dec. 31, 2014
Senior Unsecured Notes270 due 2020 [Member]
Parent Company
Unsecured Debt [Member]
Dec. 31, 2015
Senior Unsecured Notes365 due 2026 [Member]
Parent Company
Dec. 31, 2015
Senior Unsecured Notes365 due 2026 [Member]
Parent Company
Unsecured Debt [Member]
Dec. 31, 2014
Senior Unsecured Notes365 due 2026 [Member]
Parent Company
Unsecured Debt [Member]
Dec. 31, 2015
Series1993570 Due2024 [Member]
Ameren Illinois Company
Environmental Improvement And Pollution Control Revenue Bonds
May 31, 2014
Senior Unsecured Notes8875 Due2014 [Member]
Parent Company
Dec. 31, 2015
5.40% Senior secured notes due 2016
Union Electric Company
Secured Debt
Dec. 31, 2014
5.40% Senior secured notes due 2016
Union Electric Company
Secured Debt
Jun. 30, 2015
Senior Secured Notes, 3.65%, Due 2045 [Member]
Union Electric Company
Secured Debt
Dec. 31, 2015
Senior Secured Notes, 3.65%, Due 2045 [Member]
Union Electric Company
Secured Debt
Dec. 31, 2014
Senior Secured Notes, 3.65%, Due 2045 [Member]
Union Electric Company
Secured Debt
Jun. 30, 2015
Senior Secured Notes 4.75% Due2015 [Member]
Union Electric Company
Dec. 31, 2015
Senior Secured Notes 4.75% Due2015 [Member]
Union Electric Company
Secured Debt
Dec. 31, 2014
Senior Secured Notes 4.75% Due2015 [Member]
Union Electric Company
Secured Debt
Apr. 30, 2014
Senior Secured Notes, 3.50%, Due 2024 [Member]
Union Electric Company
Secured Debt
May 31, 2014
5.50% Senior secured notes due 2014
Union Electric Company
Secured Debt
May 15, 2014
5.50% Senior secured notes due 2014
Union Electric Company
Secured Debt
Dec. 31, 2015
Senior Secured Notes 4.80% Due 2043
Ameren Illinois Company
Secured Debt
Dec. 31, 2014
Senior Secured Notes 4.80% Due 2043
Ameren Illinois Company
Secured Debt
Dec. 31, 2015
1993 5.45% Series due 2028
Union Electric Company
Environmental Improvement And Pollution Control Revenue Bonds
Dec. 31, 2015
Senior Secured Notes, 4.15%, Due 2046 [Member]
Ameren Illinois Company
Secured Debt
Dec. 31, 2014
Senior Secured Notes, 4.15%, Due 2046 [Member]
Ameren Illinois Company
Secured Debt
Jun. 30, 2014
Senior Secured Notes, 4.30%, Due 2044 [Member] [Member]
Ameren Illinois Company
Secured Debt
Dec. 31, 2014
Senior Secured Notes, 3 Point 25, Due 2025 [Member]
Ameren Illinois Company
Secured Debt
Dec. 31, 2015
Senior Secured Notes, 3 Point 25, Due 2025 [Member]
Ameren Illinois Company
Secured Debt
Dec. 31, 2015
Senior Secured Notes, 2.70%, Due 2022
Ameren Illinois Company
Secured Debt
Dec. 31, 2014
Senior Secured Notes, 2.70%, Due 2022
Ameren Illinois Company
Secured Debt
Dec. 31, 2015
3.90% Senior secured notes due 2042
Union Electric Company
Secured Debt
Dec. 31, 2014
3.90% Senior secured notes due 2042
Union Electric Company
Secured Debt
Dec. 31, 2015
Series 1993 5.90% Due 2023
Ameren Illinois Company
Secured Debt
Jan. 31, 2014
Series 1993 5.90% Due 2023
Ameren Illinois Company
Environmental Improvement And Pollution Control Revenue Bonds
Dec. 31, 2015
Series 1993 5.90% Due 2023
Ameren Illinois Company
Environmental Improvement And Pollution Control Revenue Bonds
Dec. 31, 2014
Series 1993 5.90% Due 2023
Ameren Illinois Company
Environmental Improvement And Pollution Control Revenue Bonds
Dec. 31, 2015
Minimum
Ameren Illinois Company
Mar. 31, 2016
Subsequent Event
5.40% Senior secured notes due 2016
Union Electric Company
Secured Debt
Long-Term Debt And Equity Financings [Line Items]
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Debt Default Provision Excess
$ 25,000,000 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Preferred stock, authorized
100,000,000 
 
 
7,500,000.0 
 
 
2,600,000.0 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Preferred stock, par value
$ 0.01 
 
 
$ 1 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Preferred stock, shares outstanding
0 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Common stock, shares authorized
400,000,000 
400,000,000 
 
150,000,000 
150,000,000 
 
45,000,000 
45,000,000 
 
 
 
 
 
 
8,600,000.0 
4,000,000 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Repayments of Other Long-term Debt
120,000,000 
697,000,000 
399,000,000 
120,000,000 
109,000,000 
249,000,000 
0 
163,000,000 
150,000,000 
 
 
0 
425,000,000 
0 
 
 
 
 
 
 
 
 
 
 
425,000,000 
 
 
 
 
 
114,000,000 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Debt instrument face amount
 
 
 
 
 
 
 
 
 
1,000,000 1
 
 
 
 
 
 
 
 
350,000,000 
0 
 
350,000,000 
0 
1,000,000 2
 
260,000,000 3
260,000,000 3
 
250,000,000 
0 3
 
0 3
114,000,000 3
350,000,000 
 
 
280,000,000 4
280,000,000 4
1,000,000 2
250,000,000 4
0 4
250,000,000 
300,000,000 4
300,000,000 4 5
400,000,000 4 5
400,000,000 4 5
485,000,000 3 6
485,000,000 3 6
1,000,000 2
 
1,000,000 2 7
1,000,000 7
 
260,000,000 
Long-term debt interest rate
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2.70% 
2.70% 
 
3.65% 
3.65% 
 
 
8.875% 
5.40% 
 
 
3.65% 
 
4.75% 
4.75% 
 
3.50% 
 
5.50% 
4.80% 
 
5.45% 
4.15% 
 
4.30% 
 
3.25% 
2.70% 
 
3.90% 
 
5.90% 
 
5.90% 
 
 
5.40% 
Proceeds from issuance of secured debt
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
348,000,000 
 
 
347,000,000 
 
 
 
 
 
247,000,000 
 
 
 
 
 
348,000,000 
 
 
 
 
 
245,000,000 
 
246,000,000 
298,000,000 
 
 
 
 
 
 
 
 
 
 
 
Redemptions of long-term debt
 
 
 
 
 
 
 
 
 
 
$ 163,000,000 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
$ 104,000,000 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
$ 32,000,000 8
 
 
 
 
Bonds interest rate assumption
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
5.00% 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Dividend rate on preferred shares, percentage
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
6.00% 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Common stock equity to capitalization ratio
 
 
 
 
 
 
51.00% 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
30.00% 
 
[3] These notes are collaterally secured by first mortgage bonds issued by Ameren Missouri under the Ameren Missouri mortgage indenture. The notes have a fall-away lien provision and will remain secured only as long as any first mortgage bonds issued under the Ameren Missouri mortgage indenture remain outstanding. Redemption, purchase, or maturity of all first mortgage bonds, including first mortgage bonds currently outstanding and any that may be issued in the future, would result in a release of the first mortgage bonds currently securing these notes, at which time these notes would become unsecured obligations. Considering the Ameren Missouri senior secured notes currently outstanding, we do not expect the first mortgage bond lien protection associated with these notes to fall away until 2042.
[4] These notes are collaterally secured by mortgage bonds issued by Ameren Illinois under the Ameren Illinois mortgage indenture. They are secured by substantially all property of the former IP and CIPS. The notes have a fall-away lien provision and will remain secured only as long as any series of first mortgage bonds issued under the Ameren Illinois mortgage indenture remain outstanding. Redemption, purchase, or maturity of all mortgage bonds, including first mortgage bonds currently outstanding and any that may be issued in the future, would result in a release of the mortgage bonds currently securing these notes, at which time these notes would become unsecured obligations. Considering the Ameren Illinois senior secured notes currently outstanding, we do not expect the mortgage bond lien protection associated with these notes to fall away until 2024.
Long-Term Debt And Equity Financings (Schedule Of Long-Term Debt Outstanding) (Details) (USD $)
12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2015
Parent Company
Dec. 31, 2014
Parent Company
Dec. 31, 2015
Parent Company
Senior Unsecured Notes270 due 2020 [Member]
Dec. 31, 2015
Parent Company
Senior Unsecured Notes365 due 2026 [Member]
May 31, 2014
Parent Company
8.875% Senior unsecured notes due 2014
Dec. 31, 2015
Ameren Illinois Company
Dec. 31, 2014
Ameren Illinois Company
Jan. 31, 2014
Ameren Illinois Company
Dec. 31, 2015
Union Electric Company
Dec. 31, 2014
Union Electric Company
Jun. 30, 2015
Union Electric Company
Senior Secured Notes 4.75% Due2015 [Member]
Dec. 31, 2015
Union Electric Company
City Of Bowling Green Capital Lease Peno Creek Ct
Dec. 31, 2014
Union Electric Company
City Of Bowling Green Capital Lease Peno Creek Ct
Dec. 31, 2015
Union Electric Company
Audrain County Capital Lease Audrain County Ct
Dec. 31, 2014
Union Electric Company
Audrain County Capital Lease Audrain County Ct
Dec. 31, 2015
Unsecured Debt [Member]
Parent Company
Senior Unsecured Notes270 due 2020 [Member]
Dec. 31, 2014
Unsecured Debt [Member]
Parent Company
Senior Unsecured Notes270 due 2020 [Member]
Dec. 31, 2015
Unsecured Debt [Member]
Parent Company
Senior Unsecured Notes365 due 2026 [Member]
Dec. 31, 2014
Unsecured Debt [Member]
Parent Company
Senior Unsecured Notes365 due 2026 [Member]
Dec. 31, 2015
Secured Debt
Ameren Illinois Company
Senior Secured Notes 6.20% Due 2016
Dec. 31, 2014
Secured Debt
Ameren Illinois Company
Senior Secured Notes 6.20% Due 2016
Dec. 31, 2015
Secured Debt
Ameren Illinois Company
Senior Secured Notes 6.25% Due 2016
Dec. 31, 2014
Secured Debt
Ameren Illinois Company
Senior Secured Notes 6.25% Due 2016
Dec. 31, 2015
Secured Debt
Ameren Illinois Company
Senior Secured Notes 6.125% Due 2017
Dec. 31, 2014
Secured Debt
Ameren Illinois Company
Senior Secured Notes 6.125% Due 2017
Dec. 31, 2015
Secured Debt
Ameren Illinois Company
Senior Secured Notes 6.25% Due 2018
Dec. 31, 2014
Secured Debt
Ameren Illinois Company
Senior Secured Notes 6.25% Due 2018
Dec. 31, 2015
Secured Debt
Ameren Illinois Company
Senior Secured Notes 9.75% Due 2018
Dec. 31, 2014
Secured Debt
Ameren Illinois Company
Senior Secured Notes 9.75% Due 2018
Dec. 31, 2015
Secured Debt
Ameren Illinois Company
Senior Secured Notes, 2.70%, Due 2022
Dec. 31, 2014
Secured Debt
Ameren Illinois Company
Senior Secured Notes, 2.70%, Due 2022
Dec. 31, 2015
Secured Debt
Ameren Illinois Company
Senior Secured Notes, 3 Point 25, Due 2025 [Member]
Dec. 31, 2014
Secured Debt
Ameren Illinois Company
Senior Secured Notes, 3 Point 25, Due 2025 [Member]
Dec. 31, 2015
Secured Debt
Ameren Illinois Company
Senior Secured Notes 6.125% Due 2028
Dec. 31, 2014
Secured Debt
Ameren Illinois Company
Senior Secured Notes 6.125% Due 2028
Dec. 31, 2015
Secured Debt
Ameren Illinois Company
Senior Secured Notes 6.70% Due 2036
Dec. 31, 2014
Secured Debt
Ameren Illinois Company
Senior Secured Notes 6.70% Due 2036
Dec. 31, 2015
Secured Debt
Ameren Illinois Company
Senior Secured Notes 6.70% Due 2036
Dec. 31, 2014
Secured Debt
Ameren Illinois Company
Senior Secured Notes 6.70% Due 2036
Dec. 31, 2015
Secured Debt
Ameren Illinois Company
Senior Secured Notes 4.80% Due 2043
Dec. 31, 2014
Secured Debt
Ameren Illinois Company
Senior Secured Notes 4.80% Due 2043
Dec. 31, 2015
Secured Debt
Ameren Illinois Company
Senior Secured Notes430 Due2044 [Member]
Dec. 31, 2014
Secured Debt
Ameren Illinois Company
Senior Secured Notes430 Due2044 [Member]
Dec. 31, 2015
Secured Debt
Ameren Illinois Company
Senior Secured Notes, 4.15%, Due 2046 [Member]
Dec. 31, 2014
Secured Debt
Ameren Illinois Company
Senior Secured Notes, 4.15%, Due 2046 [Member]
Dec. 31, 2015
Secured Debt
Ameren Illinois Company
Series 1993 5.90% Due 2023
May 15, 2014
Secured Debt
Union Electric Company
5.50% Senior secured notes due 2014
Dec. 31, 2015
Secured Debt
Union Electric Company
Senior Secured Notes 4.75% Due2015 [Member]
Dec. 31, 2014
Secured Debt
Union Electric Company
Senior Secured Notes 4.75% Due2015 [Member]
Dec. 31, 2015
Secured Debt
Union Electric Company
5.40% Senior secured notes due 2016
Dec. 31, 2014
Secured Debt
Union Electric Company
5.40% Senior secured notes due 2016
Dec. 31, 2015
Secured Debt
Union Electric Company
6.40% Senior secured notes due 2017
Dec. 31, 2014
Secured Debt
Union Electric Company
6.40% Senior secured notes due 2017
Dec. 31, 2015
Secured Debt
Union Electric Company
6.00% Senior secured notes due 2018
Dec. 31, 2014
Secured Debt
Union Electric Company
6.00% Senior secured notes due 2018
Dec. 31, 2015
Secured Debt
Union Electric Company
5.10% Senior secured notes due 2018
Dec. 31, 2014
Secured Debt
Union Electric Company
5.10% Senior secured notes due 2018
Dec. 31, 2015
Secured Debt
Union Electric Company
6.70% Senior secured notes due 2019
Dec. 31, 2014
Secured Debt
Union Electric Company
6.70% Senior secured notes due 2019
Dec. 31, 2015
Secured Debt
Union Electric Company
5.10% Senior secured notes due 2019
Dec. 31, 2014
Secured Debt
Union Electric Company
5.10% Senior secured notes due 2019
Dec. 31, 2015
Secured Debt
Union Electric Company
5.00% Senior secured notes due 2020
Dec. 31, 2014
Secured Debt
Union Electric Company
5.00% Senior secured notes due 2020
Dec. 31, 2015
Secured Debt
Union Electric Company
Senior Secured Notes350 Due2024 [Member]
Dec. 31, 2014
Secured Debt
Union Electric Company
Senior Secured Notes350 Due2024 [Member]
Dec. 31, 2015
Secured Debt
Union Electric Company
5.50% Senior secured notes due 2034
Dec. 31, 2014
Secured Debt
Union Electric Company
5.50% Senior secured notes due 2034
Dec. 31, 2015
Secured Debt
Union Electric Company
5.30% Senior secured notes due 2037
Dec. 31, 2014
Secured Debt
Union Electric Company
5.30% Senior secured notes due 2037
Dec. 31, 2015
Secured Debt
Union Electric Company
8.45% Senior secured notes due 2039
Dec. 31, 2014
Secured Debt
Union Electric Company
8.45% Senior secured notes due 2039
Dec. 31, 2015
Secured Debt
Union Electric Company
3.90% Senior secured notes due 2042
Dec. 31, 2014
Secured Debt
Union Electric Company
3.90% Senior secured notes due 2042
Dec. 31, 2015
Secured Debt
Union Electric Company
Senior Secured Notes, 3.65%, Due 2045 [Member]
Dec. 31, 2014
Secured Debt
Union Electric Company
Senior Secured Notes, 3.65%, Due 2045 [Member]
Dec. 31, 2015
Environmental Improvement And Pollution Control Revenue Bonds
Ameren Illinois Company
Series 1993 5.90% Due 2023
Dec. 31, 2014
Environmental Improvement And Pollution Control Revenue Bonds
Ameren Illinois Company
Series 1993 5.90% Due 2023
Dec. 31, 2015
Environmental Improvement And Pollution Control Revenue Bonds
Ameren Illinois Company
Series 1994 A 5.70% Due 2024
Dec. 31, 2014
Environmental Improvement And Pollution Control Revenue Bonds
Ameren Illinois Company
Series 1994 A 5.70% Due 2024
Dec. 31, 2015
Environmental Improvement And Pollution Control Revenue Bonds
Ameren Illinois Company
Series C-1 1993 5.95% Due 2026
Dec. 31, 2015
Environmental Improvement And Pollution Control Revenue Bonds
Ameren Illinois Company
Series B-1 1993 Due 2028
Dec. 31, 2014
Environmental Improvement And Pollution Control Revenue Bonds
Ameren Illinois Company
Series B-1 1993 Due 2028
Dec. 31, 2015
Environmental Improvement And Pollution Control Revenue Bonds
Union Electric Company
1992 Series due 2022
Dec. 31, 2014
Environmental Improvement And Pollution Control Revenue Bonds
Union Electric Company
1992 Series due 2022
Dec. 31, 2015
Environmental Improvement And Pollution Control Revenue Bonds
Union Electric Company
1993 5.45% Series due 2028
Dec. 31, 2015
Environmental Improvement And Pollution Control Revenue Bonds
Union Electric Company
1998 Series A due 2033
Dec. 31, 2014
Environmental Improvement And Pollution Control Revenue Bonds
Union Electric Company
1998 Series A due 2033
Dec. 31, 2015
Environmental Improvement And Pollution Control Revenue Bonds
Union Electric Company
1998 Series B due 2033
Dec. 31, 2014
Environmental Improvement And Pollution Control Revenue Bonds
Union Electric Company
1998 Series B due 2033
Dec. 31, 2015
Environmental Improvement And Pollution Control Revenue Bonds
Union Electric Company
1998 Series C due 2033
Dec. 31, 2014
Environmental Improvement And Pollution Control Revenue Bonds
Union Electric Company
1998 Series C due 2033
Debt Instrument [Line Items]
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Debt instrument face amount
 
 
 
 
 
 
 
 
 
$ 1,000,000 1
 
 
 
 
 
 
 
$ 350,000,000 
$ 0 
$ 350,000,000 
$ 0 
$ 54,000,000 2
$ 54,000,000 2
$ 75,000,000 3
$ 75,000,000 3
$ 250,000,000 3 4
$ 250,000,000 3 4
$ 144,000,000 3 4
$ 144,000,000 3 4
$ 313,000,000 3 4
$ 313,000,000 3 4
$ 400,000,000 3 4
$ 400,000,000 3 4
$ 300,000,000 3 4
$ 300,000,000 3
$ 60,000,000 3
$ 60,000,000 3
$ 61,000,000 3
$ 61,000,000 3
$ 42,000,000 2
$ 42,000,000 2
$ 280,000,000 3
$ 280,000,000 3
$ 250,000,000 3
$ 250,000,000 3
$ 250,000,000 3
$ 0 3
$ 1,000,000 5
 
$ 0 6
$ 114,000,000 6
$ 260,000,000 6
$ 260,000,000 6
$ 425,000,000 6
$ 425,000,000 6
$ 179,000,000 6 7
$ 179,000,000 6 7
$ 199,000,000 6
$ 199,000,000 6
$ 329,000,000 6 7
$ 329,000,000 6 7
$ 244,000,000 6
$ 244,000,000 6
$ 85,000,000 6
$ 85,000,000 6
$ 350,000,000 6
$ 350,000,000 6
$ 184,000,000 6
$ 184,000,000 6
$ 300,000,000 6
$ 300,000,000 6
$ 350,000,000 6 7
$ 350,000,000 6 7
$ 485,000,000 6 7
$ 485,000,000 6 7
$ 250,000,000 
$ 0 6
$ 1,000,000 5 8
$ 1,000,000 8
$ 1,000,000 1
$ 1,000,000 1
 
$ 17,000,000 9 10
$ 17,000,000 9 10
$ 47,000,000 11 10
$ 47,000,000 11 10
$ 1,000,000 5
$ 60,000,000 11 10
$ 60,000,000 11 10
$ 50,000,000 11 10
$ 50,000,000 11 10
$ 50,000,000 11 10
$ 50,000,000 11 10
Capital lease obligations
 
 
 
 
 
 
 
 
 
 
 
 
 
48,000,000 
54,000,000 
240,000,000 
240,000,000 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Long-term debt, gross
 
 
700,000,000 
0 
 
 
 
2,496,000,000 
2,246,000,000 
 
4,135,000,000 
4,005,000,000 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Unamortized Debt Issuance Expense
 
 
(6,000,000)12
0 12
 
 
 
(18,000,000)12
(17,000,000)12
 
(19,000,000)12
(18,000,000)12
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Less: Unamortized discount and premium
 
 
 
 
 
 
 
7,000,000 
5,000,000 
 
6,000,000 
6,000,000 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Less: Maturities due within one year
(395,000,000)
(120,000,000)
 
 
 
 
 
(129,000,000)
0 
 
(266,000,000)
(120,000,000)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Long-term Debt, Net
$ 6,880,000,000 
$ 6,085,000,000 
$ 694,000,000 
$ 0 
 
 
 
$ 2,342,000,000 
$ 2,224,000,000 
 
$ 3,844,000,000 
$ 3,861,000,000 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Long-term debt interest rate
 
 
 
 
2.70% 
3.65% 
8.875% 
 
 
 
 
 
4.75% 
 
 
 
 
2.70% 
 
3.65% 
 
6.20% 
 
6.25% 
 
6.125% 
 
6.25% 
 
9.75% 
 
2.70% 
 
3.25% 
 
6.125% 
 
6.70% 
 
6.70% 
 
4.80% 
 
4.30% 
 
4.15% 
 
5.90% 
5.50% 
4.75% 
 
5.40% 
 
6.40% 
 
6.00% 
 
5.10% 
 
6.70% 
 
5.10% 
 
5.00% 
 
3.50% 
 
5.50% 
 
5.30% 
 
8.45% 
 
3.90% 
 
3.65% 
 
5.90% 
 
5.70% 
 
 
 
 
 
 
5.45% 
 
 
 
 
 
 
Long-term debt maturity date
 
 
 
 
2020 
2026 
 
 
 
 
 
 
 
2022 
 
2023 
 
 
 
 
 
2016 
 
2016 
 
2017 
 
2018 
 
2018 
 
2022 
 
2025 
 
2028 
 
2036 
 
2036 
 
2043 
 
2044 
 
 
 
 
 
2015 
 
2016 
 
2017 
 
2018 
 
2018 
 
2019 
 
2019 
 
2020 
 
2024 
 
2034 
 
2037 
 
2039 
 
2042 
 
2045 
 
2023 
 
2024 
 
 
2028 
 
2022 
 
2028 
2033 
 
2033 
 
2033 
 
Debt instrument, interest rate, maximum
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
18.00% 
 
 
18.00% 
 
18.00% 
 
18.00% 
 
Redemption price, percentage
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
100.00% 
 
100.00% 
 
100.00% 
100.00% 
 
 
 
100.00% 
 
 
 
 
 
 
[3] These notes are collaterally secured by mortgage bonds issued by Ameren Illinois under the Ameren Illinois mortgage indenture. They are secured by substantially all property of the former IP and CIPS. The notes have a fall-away lien provision and will remain secured only as long as any series of first mortgage bonds issued under the Ameren Illinois mortgage indenture remain outstanding. Redemption, purchase, or maturity of all mortgage bonds, including first mortgage bonds currently outstanding and any that may be issued in the future, would result in a release of the mortgage bonds currently securing these notes, at which time these notes would become unsecured obligations. Considering the Ameren Illinois senior secured notes currently outstanding, we do not expect the mortgage bond lien protection associated with these notes to fall away until 2024.
[6] These notes are collaterally secured by first mortgage bonds issued by Ameren Missouri under the Ameren Missouri mortgage indenture. The notes have a fall-away lien provision and will remain secured only as long as any first mortgage bonds issued under the Ameren Missouri mortgage indenture remain outstanding. Redemption, purchase, or maturity of all first mortgage bonds, including first mortgage bonds currently outstanding and any that may be issued in the future, would result in a release of the first mortgage bonds currently securing these notes, at which time these notes would become unsecured obligations. Considering the Ameren Missouri senior secured notes currently outstanding, we do not expect the first mortgage bond lien protection associated with these notes to fall away until 2042.
Long-Term Debt And Equity Financings (Schedule Of Average Interest Rates) (Details)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
1992 Series due 2022 |
Union Electric Company
 
 
Debt Instrument [Line Items]
 
 
Debt instrument, interest rate during period
0.06% 
0.10% 
1998 Series A due 2033 |
Union Electric Company
 
 
Debt Instrument [Line Items]
 
 
Debt instrument, interest rate during period
0.24% 
0.26% 
1998 Series B due 2033 |
Union Electric Company
 
 
Debt Instrument [Line Items]
 
 
Debt instrument, interest rate during period
0.24% 
0.27% 
1998 Series C due 2033 |
Union Electric Company
 
 
Debt Instrument [Line Items]
 
 
Debt instrument, interest rate during period
0.24% 
0.26% 
Series B-1 1993 Due 2028 |
Ameren Illinois Company
 
 
Debt Instrument [Line Items]
 
 
Debt instrument, interest rate during period
0.49% 
0.21% 
Secured Debt |
3.90% Senior secured notes due 2042 |
Union Electric Company
 
 
Debt Instrument [Line Items]
 
 
Long-term debt interest rate
3.90% 
 
Long-Term Debt And Equity Financings (Schedule Of Maturities Of Long-Term Debt) (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2015
Debt Instrument [Line Items]
 
2015
$ 395 
2016
681 
2017
840 
2018
581 
2019
442 
Thereafter
4,392 
Total
7,331 
Parent Company
 
Debt Instrument [Line Items]
 
2019
350 1
Thereafter
350 1
Total
700 1
Debt Instrument, Unamortized Discount or Premium and Debt Issuance Costs
(6)
Union Electric Company
 
Debt Instrument [Line Items]
 
2015
266 1
2016
431 1
2017
383 1
2018
581 1
2019
92 1
Thereafter
2,382 1
Total
4,135 1
Debt Instrument, Unamortized Discount or Premium and Debt Issuance Costs
25 
Ameren Illinois Company
 
Debt Instrument [Line Items]
 
2015
129 1
2016
250 1
2017
457 1
Thereafter
1,660 1
Total
2,496 1
Debt Instrument, Unamortized Discount or Premium and Debt Issuance Costs
$ 25 
Long-Term Debt And Equity Financings (Schedule Of Outstanding Preferred Stock) (Details) (USD $)
In Millions, except Share data, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Long-Term Debt And Equity Financings [Line Items]
 
 
Preferred stock, par value
$ 0.01 
 
Preferred stock, authorized
100,000,000 
 
Preferred stock, shares outstanding
0 
 
Preferred stock, voluntary liquidation
$ 106 
 
Union Electric Company and Ameren Illinois [Member]
 
 
Long-Term Debt And Equity Financings [Line Items]
 
 
Preferred stock, issued
$ 142 
$ 142 
Union Electric Company
 
 
Long-Term Debt And Equity Financings [Line Items]
 
 
Preferred stock, par value
$ 1 
 
Preferred stock, authorized
7,500,000 
 
Preferred stock, issued
80 
80 
Union Electric Company |
Par Value $100 [Member]
 
 
Long-Term Debt And Equity Financings [Line Items]
 
 
Preferred stock, par value
$ 100 
 
Preferred stock, authorized
25,000,000 
 
Union Electric Company |
$3.50 Series
 
 
Long-Term Debt And Equity Financings [Line Items]
 
 
Dividend rate on preferred shares, per-dollar amount
$ 3.50 
 
Preferred stock, shares outstanding
130,000 
 
Preferred stock, redemption price per share
$ 110 
 
Preferred stock, issued
13 
13 
Union Electric Company |
$3.70 Series
 
 
Long-Term Debt And Equity Financings [Line Items]
 
 
Dividend rate on preferred shares, per-dollar amount
$ 3.70 
 
Preferred stock, shares outstanding
40,000 
 
Preferred stock, redemption price per share
$ 105 
 
Preferred stock, issued
4 
4 
Union Electric Company |
$4.00 Series
 
 
Long-Term Debt And Equity Financings [Line Items]
 
 
Dividend rate on preferred shares, per-dollar amount
$ 4.00 
 
Preferred stock, shares outstanding
150,000 
 
Preferred stock, redemption price per share
$ 106 
 
Preferred stock, issued
15 
15 
Union Electric Company |
$4.30 Series
 
 
Long-Term Debt And Equity Financings [Line Items]
 
 
Dividend rate on preferred shares, per-dollar amount
$ 4.30 
 
Preferred stock, shares outstanding
40,000 
 
Preferred stock, redemption price per share
$ 105 
 
Preferred stock, issued
4 
4 
Union Electric Company |
$4.50 Series
 
 
Long-Term Debt And Equity Financings [Line Items]
 
 
Dividend rate on preferred shares, per-dollar amount
$ 4.50 
 
Preferred stock, shares outstanding
213,595 
 
Preferred stock, redemption price per share
$ 110 1
 
Preferred stock, issued
21 
21 
Union Electric Company |
$4.56 Series
 
 
Long-Term Debt And Equity Financings [Line Items]
 
 
Dividend rate on preferred shares, per-dollar amount
$ 4.56 
 
Preferred stock, shares outstanding
200,000 
 
Preferred stock, redemption price per share
$ 102 
 
Preferred stock, issued
20 
20 
Union Electric Company |
$4.75 Series
 
 
Long-Term Debt And Equity Financings [Line Items]
 
 
Dividend rate on preferred shares, per-dollar amount
$ 4.75 
 
Preferred stock, shares outstanding
20,000 
 
Preferred stock, redemption price per share
$ 102 
 
Preferred stock, issued
2 
2 
Union Electric Company |
$5.50 Series A
 
 
Long-Term Debt And Equity Financings [Line Items]
 
 
Dividend rate on preferred shares, per-dollar amount
$ 5.50 
 
Preferred stock, shares outstanding
14,000 
 
Preferred stock, redemption price per share
$ 110 
 
Preferred stock, issued
1 
1 
Ameren Illinois Company
 
 
Long-Term Debt And Equity Financings [Line Items]
 
 
Preferred stock, authorized
2,600,000 
 
Preferred stock, issued
62 
62 
Ameren Illinois Company |
Par Value $100 [Member]
 
 
Long-Term Debt And Equity Financings [Line Items]
 
 
Preferred stock, par value
$ 100 
 
Preferred stock, authorized
2,000,000 
 
Ameren Illinois Company |
4.00% Series
 
 
Long-Term Debt And Equity Financings [Line Items]
 
 
Dividend rate on preferred shares, percentage
4.00% 
 
Preferred stock, shares outstanding
144,275 
 
Preferred stock, redemption price per share
$ 101 
 
Preferred stock, issued
14 
14 
Ameren Illinois Company |
4.08% Series
 
 
Long-Term Debt And Equity Financings [Line Items]
 
 
Dividend rate on preferred shares, percentage
4.08% 
 
Preferred stock, shares outstanding
45,224 
 
Preferred stock, redemption price per share
$ 103 
 
Preferred stock, issued
5 
5 
Ameren Illinois Company |
4.20% Series
 
 
Long-Term Debt And Equity Financings [Line Items]
 
 
Dividend rate on preferred shares, percentage
4.20% 
 
Preferred stock, shares outstanding
23,655 
 
Preferred stock, redemption price per share
$ 104 
 
Preferred stock, issued
2 
2 
Ameren Illinois Company |
4.25% Series
 
 
Long-Term Debt And Equity Financings [Line Items]
 
 
Dividend rate on preferred shares, percentage
4.25% 
 
Preferred stock, shares outstanding
50,000 
 
Preferred stock, redemption price per share
$ 102 
 
Preferred stock, issued
5 
5 
Ameren Illinois Company |
4.26% Series
 
 
Long-Term Debt And Equity Financings [Line Items]
 
 
Dividend rate on preferred shares, percentage
4.26% 
 
Preferred stock, shares outstanding
16,621 
 
Preferred stock, redemption price per share
$ 103 
 
Preferred stock, issued
2 
2 
Ameren Illinois Company |
4.42% Series
 
 
Long-Term Debt And Equity Financings [Line Items]
 
 
Dividend rate on preferred shares, percentage
4.42% 
 
Preferred stock, shares outstanding
16,190 
 
Preferred stock, redemption price per share
$ 103 
 
Preferred stock, issued
2 
2 
Ameren Illinois Company |
4.70% Series
 
 
Long-Term Debt And Equity Financings [Line Items]
 
 
Dividend rate on preferred shares, percentage
4.70% 
 
Preferred stock, shares outstanding
18,429 
 
Preferred stock, redemption price per share
$ 103 
 
Preferred stock, issued
2 
2 
Ameren Illinois Company |
4.90% Series
 
 
Long-Term Debt And Equity Financings [Line Items]
 
 
Dividend rate on preferred shares, percentage
4.90% 
 
Preferred stock, shares outstanding
73,825 
 
Preferred stock, redemption price per share
$ 102 
 
Preferred stock, issued
7 
7 
Ameren Illinois Company |
4.92% Series
 
 
Long-Term Debt And Equity Financings [Line Items]
 
 
Dividend rate on preferred shares, percentage
4.92% 
 
Preferred stock, shares outstanding
49,289 
 
Preferred stock, redemption price per share
$ 104 
 
Preferred stock, issued
5 
5 
Ameren Illinois Company |
5.16% Series
 
 
Long-Term Debt And Equity Financings [Line Items]
 
 
Dividend rate on preferred shares, percentage
5.16% 
 
Preferred stock, shares outstanding
50,000 
 
Preferred stock, redemption price per share
$ 102 
 
Preferred stock, issued
5 
5 
Ameren Illinois Company |
6.625% Series
 
 
Long-Term Debt And Equity Financings [Line Items]
 
 
Dividend rate on preferred shares, percentage
6.625% 
 
Preferred stock, shares outstanding
124,274 
 
Preferred stock, redemption price per share
$ 100 
 
Preferred stock, issued
12 
12 
Ameren Illinois Company |
7.75% Series
 
 
Long-Term Debt And Equity Financings [Line Items]
 
 
Dividend rate on preferred shares, percentage
7.75% 
 
Preferred stock, shares outstanding
4,542 
 
Preferred stock, redemption price per share
$ 100 
 
Preferred stock, issued
$ 1 
$ 1 
Long-Term Debt and Equity Financings (Schedule of Debt Redemptions) (Details) (Ameren Illinois Company, USD $)
1 Months Ended
Jan. 31, 2014
Dec. 31, 2015
Dec. 31, 2014
Debt Instrument [Line Items]
 
 
 
Debt instrument face amount
$ 1,000,000 1
 
 
Secured Debt |
Senior Secured Notes 9.75% Due 2018
 
 
 
Debt Instrument [Line Items]
 
 
 
Debt instrument face amount
 
313,000,000 2 3
313,000,000 2 3
Secured Debt |
Series 1993 5.90% Due 2023
 
 
 
Debt Instrument [Line Items]
 
 
 
Debt instrument face amount
 
1,000,000 4
 
Secured Debt |
Senior Secured Notes 6.25% Due 2018
 
 
 
Debt Instrument [Line Items]
 
 
 
Debt instrument face amount
 
144,000,000 2 3
144,000,000 2 3
Environmental Improvement And Pollution Control Revenue Bonds
 
 
 
Debt Instrument [Line Items]
 
 
 
Redemptions of long-term debt
163,000,000 
 
 
Environmental Improvement And Pollution Control Revenue Bonds |
Series 1993 5.90% Due 2023
 
 
 
Debt Instrument [Line Items]
 
 
 
Redemptions of long-term debt
32,000,000 5
 
 
Debt instrument face amount
 
1,000,000 4 6
1,000,000 6
Environmental Improvement And Pollution Control Revenue Bonds |
Series 1994 A 5.70% Due 2024
 
 
 
Debt Instrument [Line Items]
 
 
 
Redemptions of long-term debt
36,000,000 5
 
 
Debt instrument face amount
 
1,000,000 1
1,000,000 1
Environmental Improvement And Pollution Control Revenue Bonds |
Series C-1 1993 5.95% Due 2026
 
 
 
Debt Instrument [Line Items]
 
 
 
Redemptions of long-term debt
35,000,000 
 
 
Environmental Improvement And Pollution Control Revenue Bonds |
Series C-2 1993 5.70% Due 2026
 
 
 
Debt Instrument [Line Items]
 
 
 
Redemptions of long-term debt
8,000,000 
 
 
Environmental Improvement And Pollution Control Revenue Bonds |
Series1998A 5.40% Due 2028
 
 
 
Debt Instrument [Line Items]
 
 
 
Redemptions of long-term debt
19,000,000 
 
 
Environmental Improvement And Pollution Control Revenue Bonds |
Series1998B 5.40% Due 2028
 
 
 
Debt Instrument [Line Items]
 
 
 
Redemptions of long-term debt
$ 33,000,000 
 
 
[2] These notes are collaterally secured by mortgage bonds issued by Ameren Illinois under the Ameren Illinois mortgage indenture. They are secured by substantially all property of the former IP and CIPS. The notes have a fall-away lien provision and will remain secured only as long as any series of first mortgage bonds issued under the Ameren Illinois mortgage indenture remain outstanding. Redemption, purchase, or maturity of all mortgage bonds, including first mortgage bonds currently outstanding and any that may be issued in the future, would result in a release of the mortgage bonds currently securing these notes, at which time these notes would become unsecured obligations. Considering the Ameren Illinois senior secured notes currently outstanding, we do not expect the mortgage bond lien protection associated with these notes to fall away until 2024.
Long-Term Debt and Equity Financings (Schedule of Required and Actual Debt Ratios) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Union Electric Company
 
Debt Instrument [Line Items]
 
Bonds Issuable Based On Coverage Ratio
$ 3,385 1
Preferred Stock Issuable Based On Coverage Ratio
2,315 
Retired Bond Capacity
946 
Union Electric Company |
Actual Interest Coverage Ratio
 
Debt Instrument [Line Items]
 
Interest Coverage Ratio
3.8 
Dividend Coverage Ratio
104.0 
Ameren Illinois Company
 
Debt Instrument [Line Items]
 
Bonds Issuable Based On Coverage Ratio
3,566 1 2
Preferred Stock Issuable Based On Coverage Ratio
203 3
Retired Bond Capacity
$ 204 
Ameren Illinois Company |
Actual Interest Coverage Ratio
 
Debt Instrument [Line Items]
 
Interest Coverage Ratio
6.3 
Dividend Coverage Ratio
2.6 
Minimum |
Union Electric Company |
Required Dividend Coverage Ratio
 
Debt Instrument [Line Items]
 
Interest Coverage Ratio
2.0 4
Dividend Coverage Ratio
2.5 5
Minimum |
Ameren Illinois Company |
Required Dividend Coverage Ratio
 
Debt Instrument [Line Items]
 
Interest Coverage Ratio
2.0 4
Dividend Coverage Ratio
1.5 5
Other Income And Expenses (Other Income And Expenses) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Other Nonoperating Income (Expense) [Line Items]
 
 
 
Allowance for equity funds used during construction
$ 30 1
$ 34 1
$ 37 1
Interest income on industrial development revenue bonds
27 1
27 1
27 1
Interest and dividend income
14 1 2
10 1 2
3 1 2
Other
3 1
8 1 3
2 1
Total miscellaneous income
74 1
79 1
69 1
Donations
15 1
10 1
12 1
Other
15 1
12 1
14 1
Total miscellaneous expense
30 1
22 1
26 1
Union Electric Company
 
 
 
Other Nonoperating Income (Expense) [Line Items]
 
 
 
Allowance for equity funds used during construction
22 
32 
31 
Interest income on industrial development revenue bonds
27 
27 
27 
Interest and dividend income
1 
1 
0 
Other
2 
0 
0 
Total miscellaneous income
52 
60 
58 
Donations
5 
6 
4 
Other
6 
6 
7 
Total miscellaneous expense
11 
12 
11 
Ameren Illinois Company
 
 
 
Other Nonoperating Income (Expense) [Line Items]
 
 
 
Allowance for equity funds used during construction
8 
2 
6 
Interest and dividend income
12 2
7 2
2 2
Other
1 
8 3
2 
Total miscellaneous income
21 
17 
10 
Donations
5 
4 
4 
Other
7 
4 
5 
Total miscellaneous expense
$ 12 
$ 8 
$ 9 
Derivative Financial Instruments (Open Gross Derivative Volumes By Commodity Type) (Details)
Dec. 31, 2015
gal
Dec. 31, 2014
gal
Fuel Oils
 
 
Derivative [Line Items]
 
 
Quantity
35,000,000 1
50,000,000 1
Natural Gas
 
 
Derivative [Line Items]
 
 
Quantity
181,000,000 
136,000,000 
Power
 
 
Derivative [Line Items]
 
 
Quantity
11,000,000 
12,000,000 
Uranium
 
 
Derivative [Line Items]
 
 
Quantity
494,000 
332,000 
Union Electric Company |
Fuel Oils
 
 
Derivative [Line Items]
 
 
Quantity
35,000,000 1
50,000,000 1
Union Electric Company |
Natural Gas
 
 
Derivative [Line Items]
 
 
Quantity
30,000,000 
28,000,000 
Union Electric Company |
Power
 
 
Derivative [Line Items]
 
 
Quantity
1,000,000 
1,000,000 
Union Electric Company |
Uranium
 
 
Derivative [Line Items]
 
 
Quantity
494,000 
332,000 
Ameren Illinois Company |
Natural Gas
 
 
Derivative [Line Items]
 
 
Quantity
151,000,000 
108,000,000 
Ameren Illinois Company |
Power
 
 
Derivative [Line Items]
 
 
Quantity
10,000,000 
11,000,000 
Derivative Financial Instruments (Derivative Instruments Carrying Value) (Details) (Not Designated As Hedging Instrument, USD $)
In Millions, unless otherwise specified
Dec. 31, 2015
Dec. 31, 2014
Derivative [Line Items]
 
 
Derivative assets
$ 18 1
$ 19 1
Derivative liabilities
264 2
232 2
Fuel Oils |
Other current assets
 
 
Derivative [Line Items]
 
 
Derivative assets
 
2 
Fuel Oils |
Other current liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
22 
22 
Fuel Oils |
Other deferred credits and liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
7 
7 
Natural Gas |
Other current assets
 
 
Derivative [Line Items]
 
 
Derivative assets
1 
2 
Natural Gas |
Other assets
 
 
Derivative [Line Items]
 
 
Derivative assets
1 
 
Natural Gas |
Other current liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
38 
37 
Natural Gas |
Other deferred credits and liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
26 
19 
Power |
Other current assets
 
 
Derivative [Line Items]
 
 
Derivative assets
16 
15 
Power |
Other current liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
13 
14 
Power |
Other deferred credits and liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
157 
131 
Uranium |
Other current liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
1 
2 
Union Electric Company
 
 
Derivative [Line Items]
 
 
Derivative assets
17 1
18 1
Derivative liabilities
44 2
46 2
Union Electric Company |
Fuel Oils |
Other current assets
 
 
Derivative [Line Items]
 
 
Derivative assets
 
2 
Union Electric Company |
Fuel Oils |
Other current liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
22 
22 
Union Electric Company |
Fuel Oils |
Other deferred credits and liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
7 
7 
Union Electric Company |
Natural Gas |
Other current assets
 
 
Derivative [Line Items]
 
 
Derivative assets
 
1 
Union Electric Company |
Natural Gas |
Other assets
 
 
Derivative [Line Items]
 
 
Derivative assets
1 
 
Union Electric Company |
Natural Gas |
Other current liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
6 
6 
Union Electric Company |
Natural Gas |
Other deferred credits and liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
8 
6 
Union Electric Company |
Power |
Other current assets
 
 
Derivative [Line Items]
 
 
Derivative assets
16 
15 
Union Electric Company |
Power |
Other current liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
 
3 
Union Electric Company |
Uranium |
Other current liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
1 
2 
Ameren Illinois Company
 
 
Derivative [Line Items]
 
 
Derivative assets
1 1
1 1
Derivative liabilities
220 2
186 2
Ameren Illinois Company |
Natural Gas |
Other current assets
 
 
Derivative [Line Items]
 
 
Derivative assets
1 
1 
Ameren Illinois Company |
Natural Gas |
MTM derivative liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
32 
31 
Ameren Illinois Company |
Natural Gas |
Other deferred credits and liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
18 
13 
Ameren Illinois Company |
Power |
MTM derivative liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
13 
11 
Ameren Illinois Company |
Power |
Other deferred credits and liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
$ 157 
$ 131 
Derivative Financial Instruments Derivative Financial Instruments (Offsetting Derivative Assets and Liabilities) (Details) (Commodity Contract, USD $)
In Millions, unless otherwise specified
Dec. 31, 2015
Dec. 31, 2014
Offsetting Assets and Liabilities [Line Items]
 
 
Gross Amounts Recognized in the Balance Sheet
$ 18 1
$ 19 1
Derivative Instruments
1 
5 
Net Amount
17 
14 
Gross Amounts Recognized in the Balance Sheet
264 1
232 1
Derivative Instruments
1 
5 
Cash Collateral Received/Posted
11 2
5 2
Net Amount
252 
222 
Union Electric Company
 
 
Offsetting Assets and Liabilities [Line Items]
 
 
Gross Amounts Recognized in the Balance Sheet
17 1
18 1
Derivative Instruments
1 
5 
Net Amount
16 
13 
Gross Amounts Recognized in the Balance Sheet
44 1
46 1
Derivative Instruments
1 
5 
Cash Collateral Received/Posted
8 2
5 2
Net Amount
35 
36 
Ameren Illinois Company
 
 
Offsetting Assets and Liabilities [Line Items]
 
 
Gross Amounts Recognized in the Balance Sheet
1 
1 
Net Amount
1 
1 
Gross Amounts Recognized in the Balance Sheet
220 1
186 1
Cash Collateral Received/Posted
3 2
 
Net Amount
$ 217 
$ 186 
Fair Value Measurements (Schedule of Valuation Process and Unobservable Inputs) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Discounted Cash Flow |
Minimum |
Fuel Oils
 
 
Fair Value Inputs [Abstract]
 
 
Escalation rate
 
5.00% 1 2
Counterparty credit risk
 
0.43% 3 4
Discounted Cash Flow |
Minimum |
Natural Gas
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
0.40% 3 4
0.43% 3 4
Credit risk
0.40% 3 4
0.43% 3 4
Nodal basis
(0.10)2
(0.40)2
Discounted Cash Flow |
Minimum |
Power
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
0.86% 3 4
0.26% 3 4
Credit risk
0.40% 3 4
0.43% 3 4
Average bid/ask consensus peak and off-peak pricing
22 5
27 5
Estimated auction price for FTRs
(270)2
(1,833)2
Nodal basis
(10)5
(6)2
Discounted Cash Flow |
Minimum |
Uranium
 
 
Fair Value Inputs [Abstract]
 
 
Credit risk
0.40% 3 4
 
Average bid/ask consensus pricing
35 2
35 2
Discounted Cash Flow |
Maximum |
Fuel Oils
 
 
Fair Value Inputs [Abstract]
 
 
Escalation rate
 
5.00% 1 2
Counterparty credit risk
 
0.43% 3 4
Discounted Cash Flow |
Maximum |
Natural Gas
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
12.00% 3 4
13.00% 3 4
Credit risk
0.40% 3 4
0.43% 3 4
Nodal basis
0 2
0.10 2
Discounted Cash Flow |
Maximum |
Power
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
0.86% 3 4
0.26% 3 4
Credit risk
0.40% 3 4
0.43% 3 4
Average bid/ask consensus peak and off-peak pricing
39 5
50 5
Estimated auction price for FTRs
2,057 2
2,743 2
Nodal basis
(1)5
0 2
Discounted Cash Flow |
Maximum |
Uranium
 
 
Fair Value Inputs [Abstract]
 
 
Credit risk
0.40% 3 4
 
Average bid/ask consensus pricing
42 2
40 2
Discounted Cash Flow |
Weighted Average |
Fuel Oils
 
 
Fair Value Inputs [Abstract]
 
 
Escalation rate
 
5.00% 1 2
Counterparty credit risk
 
0.43% 3 4
Discounted Cash Flow |
Weighted Average |
Natural Gas
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
7.00% 3 4
3.00% 3 4
Credit risk
0.40% 3 4
0.43% 3 4
Nodal basis
(0.10)2
(0.20)2
Discounted Cash Flow |
Weighted Average |
Power
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
0.86% 3 4
0.26% 3 4
Credit risk
0.40% 3 4
0.43% 3 4
Average bid/ask consensus peak and off-peak pricing
29 5
32 5
Estimated auction price for FTRs
211 2
171 2
Nodal basis
(3)5
(2)2
Discounted Cash Flow |
Weighted Average |
Uranium
 
 
Fair Value Inputs [Abstract]
 
 
Credit risk
0.40% 3 4
 
Average bid/ask consensus pricing
37 2
36 2
Option Model |
Minimum |
Fuel Oils
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
 
3.00% 4
Option Model |
Minimum |
Natural Gas
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
35.00% 2
31.00% 4
Nodal basis
(0.30)4
(0.40)2
Option Model |
Minimum |
Uranium
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
20.00% 2
 
Option Model |
Maximum |
Fuel Oils
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
 
39.00% 4
Option Model |
Maximum |
Natural Gas
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
55.00% 2
144.00% 4
Nodal basis
0 4
0 2
Option Model |
Maximum |
Uranium
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
20.00% 2
 
Option Model |
Weighted Average |
Fuel Oils
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
 
32.00% 4
Option Model |
Weighted Average |
Natural Gas
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
45.00% 2
63.00% 4
Nodal basis
(0.20)4
(0.20)2
Option Model |
Weighted Average |
Uranium
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
20.00% 2
 
Fundamental Energy Production Model |
Minimum |
Power
 
 
Fair Value Inputs [Abstract]
 
 
Escalation rate
3.00% 2 6
0.00% 2 6
Estimated future gas prices
3 2
4 2
Fundamental Energy Production Model |
Maximum |
Power
 
 
Fair Value Inputs [Abstract]
 
 
Escalation rate
3.00% 2 6
1.00% 2 6
Estimated future gas prices
4 2
5 2
Fundamental Energy Production Model |
Weighted Average |
Power
 
 
Fair Value Inputs [Abstract]
 
 
Escalation rate
3.00% 2 6
1.00% 2 6
Estimated future gas prices
4 2
4 2
Contract Price Allocation |
Minimum |
Power
 
 
Fair Value Inputs [Abstract]
 
 
Estimated renewable energy credit costs
5 2
5 2
Contract Price Allocation |
Maximum |
Power
 
 
Fair Value Inputs [Abstract]
 
 
Estimated renewable energy credit costs
7 2
7 2
Contract Price Allocation |
Weighted Average |
Power
 
 
Fair Value Inputs [Abstract]
 
 
Estimated renewable energy credit costs
6 2
6 2
Derivative liabilities |
Fuel Oils
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative liabilities
 
$ (8)7
Derivative liabilities |
Natural Gas
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative liabilities
(1)7
(2)7
Derivative liabilities |
Power
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative liabilities
(170)7 8
(144)7 8
Derivative liabilities |
Uranium
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative liabilities
(1)7
(2)7
Derivative assets |
Natural Gas
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative assets
1 7
 
Derivative assets |
Power
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative assets
$ 16 7 8
 
Fair Value Measurements (Schedule Of Fair Value Hierarchy Of Assets And Liabilities Measured At Fair Value On Recurring Basis) (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2015
Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
$ 557 1
$ 547 2
Assets
575 3
566 3
Excluded receivables, payables, and accrued income, net
(1)
2 
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
368 
365 
Assets
368 3
365 3
Significant Other Observable Inputs (Level 2)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
189 
182 
Assets
190 3
187 3
Significant Other Unobservable Inputs (Level 3)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Assets
17 3
14 3
Cash And Cash Equivalents
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
4 
1 
Cash And Cash Equivalents |
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
4 
1 
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
18 3
19 3
Derivative liabilities
264 3
232 3
Commodity Contract |
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
30 3
22 3
Commodity Contract |
Significant Other Observable Inputs (Level 2)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
1 3
5 3
Derivative liabilities
62 3
54 3
Commodity Contract |
Significant Other Unobservable Inputs (Level 3)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
17 3
14 3
Derivative liabilities
172 3
156 3
Commodity Contract |
Fuel Oils
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
 
2 3
Derivative liabilities
29 3
29 3
Commodity Contract |
Fuel Oils |
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
29 3
21 3
Commodity Contract |
Fuel Oils |
Significant Other Unobservable Inputs (Level 3)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
 
2 3
Derivative liabilities
   3
8 3
Commodity Contract |
Natural Gas
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
2 3
2 3
Derivative liabilities
64 3
56 3
Commodity Contract |
Natural Gas |
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
1 3
1 3
Commodity Contract |
Natural Gas |
Significant Other Observable Inputs (Level 2)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
1 3
1 3
Derivative liabilities
62 3
53 3
Commodity Contract |
Natural Gas |
Significant Other Unobservable Inputs (Level 3)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
1 3
1 3
Derivative liabilities
1 3
2 3
Commodity Contract |
Power
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
16 3
15 3
Derivative liabilities
170 3
145 3
Commodity Contract |
Power |
Significant Other Observable Inputs (Level 2)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
 
4 3
Derivative liabilities
 
1 3
Commodity Contract |
Power |
Significant Other Unobservable Inputs (Level 3)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
16 3
11 3
Derivative liabilities
170 3
144 3
Commodity Contract |
Uranium
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
1 3
2 3
Commodity Contract |
Uranium |
Significant Other Unobservable Inputs (Level 3)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
1 3
2 3
Equity Securities |
U.S. Large Capitalization
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
364 
364 
Equity Securities |
U.S. Large Capitalization |
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
364 
364 
Debt Securities |
Corporate Bonds
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
58 
63 
Debt Securities |
Corporate Bonds |
Significant Other Observable Inputs (Level 2)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
58 
63 
Debt Securities |
U.S. treasury and agency securities
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
109 
102 
Debt Securities |
U.S. treasury and agency securities |
Significant Other Observable Inputs (Level 2)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
109 
102 
Debt Securities |
Other debt securities
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
22 
17 
Debt Securities |
Other debt securities |
Significant Other Observable Inputs (Level 2)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
22 
17 
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
557 1
547 2
Assets
574 3
565 3
Union Electric Company |
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
368 
365 
Assets
368 3
365 3
Union Electric Company |
Significant Other Observable Inputs (Level 2)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
189 
182 
Assets
189 3
187 3
Union Electric Company |
Significant Other Unobservable Inputs (Level 3)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Assets
17 3
13 3
Union Electric Company |
Cash And Cash Equivalents
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
4 
1 
Union Electric Company |
Cash And Cash Equivalents |
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
4 
1 
Union Electric Company |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
17 3
18 3
Derivative liabilities
44 3
46 3
Union Electric Company |
Commodity Contract |
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
29 3
22 3
Union Electric Company |
Commodity Contract |
Significant Other Observable Inputs (Level 2)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
 
5 3
Derivative liabilities
13 3
11 3
Union Electric Company |
Commodity Contract |
Significant Other Unobservable Inputs (Level 3)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
17 3
13 3
Derivative liabilities
2 3
13 3
Union Electric Company |
Commodity Contract |
Fuel Oils
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
 
2 3
Derivative liabilities
29 3
29 3
Union Electric Company |
Commodity Contract |
Fuel Oils |
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
29 3
21 3
Union Electric Company |
Commodity Contract |
Fuel Oils |
Significant Other Unobservable Inputs (Level 3)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
 
2 3
Derivative liabilities
 
8 3
Union Electric Company |
Commodity Contract |
Natural Gas
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
1 3
1 3
Derivative liabilities
14 3
12 3
Union Electric Company |
Commodity Contract |
Natural Gas |
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
 
1 3
Union Electric Company |
Commodity Contract |
Natural Gas |
Significant Other Observable Inputs (Level 2)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
 
1 3
Derivative liabilities
13 3
10 3
Union Electric Company |
Commodity Contract |
Natural Gas |
Significant Other Unobservable Inputs (Level 3)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
1 3
 
Derivative liabilities
1 3
1 3
Union Electric Company |
Commodity Contract |
Power
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
16 3
15 3
Derivative liabilities
0 3
3 3
Union Electric Company |
Commodity Contract |
Power |
Significant Other Observable Inputs (Level 2)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
 
4 3
Derivative liabilities
 
1 3
Union Electric Company |
Commodity Contract |
Power |
Significant Other Unobservable Inputs (Level 3)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
16 3
11 3
Derivative liabilities
 
2 3
Union Electric Company |
Commodity Contract |
Uranium
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
1 3
2 3
Union Electric Company |
Commodity Contract |
Uranium |
Significant Other Unobservable Inputs (Level 3)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
1 3
2 3
Union Electric Company |
Equity Securities |
U.S. Large Capitalization
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
364 
364 
Union Electric Company |
Equity Securities |
U.S. Large Capitalization |
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
364 
364 
Union Electric Company |
Debt Securities |
Corporate Bonds
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
58 
63 
Union Electric Company |
Debt Securities |
Corporate Bonds |
Significant Other Observable Inputs (Level 2)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
58 
63 
Union Electric Company |
Debt Securities |
U.S. treasury and agency securities
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
109 
102 
Union Electric Company |
Debt Securities |
U.S. treasury and agency securities |
Significant Other Observable Inputs (Level 2)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
109 
102 
Union Electric Company |
Debt Securities |
Other debt securities
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
22 
17 
Union Electric Company |
Debt Securities |
Other debt securities |
Significant Other Observable Inputs (Level 2)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
22 
17 
Ameren Illinois Company |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
1 
1 
Derivative liabilities
220 3
186 3
Ameren Illinois Company |
Commodity Contract |
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
1 3
0 3
Ameren Illinois Company |
Commodity Contract |
Significant Other Observable Inputs (Level 2)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
49 3
43 3
Ameren Illinois Company |
Commodity Contract |
Significant Other Unobservable Inputs (Level 3)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
170 3
143 3
Ameren Illinois Company |
Commodity Contract |
Natural Gas
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
1 3
1 3
Derivative liabilities
50 3
44 3
Ameren Illinois Company |
Commodity Contract |
Natural Gas |
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
1 3
 
Ameren Illinois Company |
Commodity Contract |
Natural Gas |
Significant Other Observable Inputs (Level 2)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
1 3
 
Derivative liabilities
49 3
43 3
Ameren Illinois Company |
Commodity Contract |
Natural Gas |
Significant Other Unobservable Inputs (Level 3)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
 
1 3
Derivative liabilities
 
1 3
Ameren Illinois Company |
Commodity Contract |
Power
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
170 3
142 3
Ameren Illinois Company |
Commodity Contract |
Power |
Significant Other Unobservable Inputs (Level 3)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
$ 170 3
$ 142 3
Fair Value Measurements (Schedule Of Changes In The Fair Value Of Financial Assets And Liabilities Classified As Level 3 In The Fair Value Hierarchy) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Fuel Oils
 
 
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
 
 
Beginning balance
$ (6)
$ 5 
Included in regulatory assets/liabilities
(1)
(9)
Settlements
5 
(2)
Transfers out of Level 3
2 
 
Ending balance
0 
(6)
Change in unrealized gains (losses) related to assets/liabilities still held
0 
(6)
Natural Gas
 
 
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
 
 
Beginning balance
(1)
0 
Included in regulatory assets/liabilities
1 
1 
Purchases
 
(2)
Sales
 
(1)
Settlements
0 
1 
Ending balance
0 
(1)
Change in unrealized gains (losses) related to assets/liabilities still held
0 
2 
Power
 
 
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
 
 
Beginning balance
(133)
(89)
Included in regulatory assets/liabilities
(39)
(53)
Purchases
29 
34 
Sales
 
(1)
Settlements
(10)
(24)
Transfers out of Level 3
(1)
 
Ending balance
(154)
(133)
Change in unrealized gains (losses) related to assets/liabilities still held
(39)
(43)
Uranium
 
 
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
 
 
Beginning balance
(2)
(6)
Included in regulatory assets/liabilities
(1)
(1)
Settlements
2 
5 
Ending balance
(1)
(2)
Change in unrealized gains (losses) related to assets/liabilities still held
0 
(1)
Union Electric Company |
Fuel Oils
 
 
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
 
 
Beginning balance
(6)
5 
Included in regulatory assets/liabilities
(1)
(9)
Settlements
5 
(2)
Transfers out of Level 3
2 
 
Ending balance
0 
(6)
Change in unrealized gains (losses) related to assets/liabilities still held
0 
(6)
Union Electric Company |
Natural Gas
 
 
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
 
 
Beginning balance
(1)
0 
Sales
 
(1)
Settlements
1 
 
Ending balance
0 
(1)
Change in unrealized gains (losses) related to assets/liabilities still held
0 
0 
Union Electric Company |
Power
 
 
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
 
 
Beginning balance
9 
19 
Included in regulatory assets/liabilities
2 
(14)
Purchases
29 
34 
Sales
 
(1)
Settlements
(23)
(29)
Transfers out of Level 3
(1)
 
Ending balance
16 
9 
Change in unrealized gains (losses) related to assets/liabilities still held
0 
0 
Union Electric Company |
Uranium
 
 
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
 
 
Beginning balance
(2)
(6)
Included in regulatory assets/liabilities
(1)
(1)
Settlements
2 
5 
Ending balance
(1)
(2)
Change in unrealized gains (losses) related to assets/liabilities still held
0 
(1)
Ameren Illinois Company |
Natural Gas
 
 
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
 
 
Beginning balance
0 
0 
Included in regulatory assets/liabilities
1 
1 
Purchases
 
(2)
Settlements
(1)
1 
Ending balance
0 
0 
Change in unrealized gains (losses) related to assets/liabilities still held
0 
2 
Ameren Illinois Company |
Power
 
 
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
 
 
Beginning balance
(142)
(108)
Included in regulatory assets/liabilities
(41)
(39)
Settlements
13 
5 
Ending balance
(170)
(142)
Change in unrealized gains (losses) related to assets/liabilities still held
$ (39)
$ (43)
Fair Value Measurements (Schedule Of Carrying Amounts And Estimated Fair Values Of Long-Term Debt And Preferred Stock) (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2015
Dec. 31, 2014
Carrying Amount
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Long-term Debt and Capital Lease Obligations
$ 7,275 1
$ 6,205 1
Preferred stock
142 1
142 1
Fair Value
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Long-term debt and capital lease obligations (including current portion)
7,814 1
7,135 1
Preferred stock
125 1
122 1
Union Electric Company |
Carrying Amount
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Long-term Debt and Capital Lease Obligations
4,110 
3,981 
Preferred stock
80 
80 
Union Electric Company |
Fair Value
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Long-term debt and capital lease obligations (including current portion)
4,449 
4,518 
Preferred stock
75 
73 
Ameren Illinois Company |
Carrying Amount
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Long-term Debt and Capital Lease Obligations
2,471 
2,224 
Preferred stock
62 
62 
Ameren Illinois Company |
Fair Value
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Long-term debt and capital lease obligations (including current portion)
2,665 
2,517 
Preferred stock
$ 50 
$ 49 
Nuclear Decommissioning Trust Fund Investments (Fair Values Of Investments In Debt And Equity Securities In Nuclear Decommissioning Trust Fund) (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2015
Dec. 31, 2014
Nuclear Decommissioning Trust Fund Investments [Line Items]
 
 
Cost
$ 341 
$ 316 
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax
226 
237 
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax
11 
4 
Fair Value
556 
549 
Debt Securities
 
 
Nuclear Decommissioning Trust Fund Investments [Line Items]
 
 
Cost
191 
175 
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax
2 
7 
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax
4 
0 
Fair Value
189 
182 
Equity Securities
 
 
Nuclear Decommissioning Trust Fund Investments [Line Items]
 
 
Cost
147 
138 
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax
224 
230 
Available-for-sale Equity Securities, Accumulated Gross Unrealized Loss, before Tax
7 
4 
Fair Value
364 
364 
Cash
 
 
Nuclear Decommissioning Trust Fund Investments [Line Items]
 
 
Cost
4 
1 
Fair Value
4 
1 
Other Debt And Equity Securities
 
 
Nuclear Decommissioning Trust Fund Investments [Line Items]
 
 
Cost
(1)
2 
Fair Value
$ (1)
$ 2 
Nuclear Decommissioning Trust Fund Investments (Costs And Fair Values Of Investments In Debt Securities In Nuclear Decommissioning Trust Fund According To Contractual Maturities) (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
 
Cost, Less than 5 years
$ 106 
Cost, 5 years to 10 years
42 
Cost, Due after 10 years
43 
Cost, Total
191 
Fair Value, Less than 5 years
105 
Fair Value, 5 years to 10 years
41 
Fair Value, Due after 10 years
43 
Fair Value, Total
$ 189 
Nuclear Decommissioning Trust Fund Investments (Fair Value And The Gross Unrealized Losses Of The Available-For-Sale Securities Held In Nuclear Decommissioning Trust Fund) (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2015
Nuclear Decommissioning Trust Fund Investments [Line Items]
 
Less than 12 months, fair value
$ 152 
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss
6 
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss
5 
12 months or greater, fair value
8 
Total, fair value
160 
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss
11 
Debt Securities
 
Nuclear Decommissioning Trust Fund Investments [Line Items]
 
Less than 12 months, fair value
136 
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss
3 
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss
1 
12 months or greater, fair value
4 
Total, fair value
140 
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss
4 
Equity Securities
 
Nuclear Decommissioning Trust Fund Investments [Line Items]
 
Less than 12 months, fair value
16 
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss
3 
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss
4 
12 months or greater, fair value
4 
Total, fair value
20 
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss
$ 7 
Callaway Energy Center (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
mill
Loss Contingencies [Line Items]
 
Nwf Fee Number Of Mills
1 
Nuclear Plant
 
Loss Contingencies [Line Items]
 
Annual decommissioning costs included in costs of service
$ 7 
Retirement Benefits (Narrative) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
bond
Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
 
 
Defined Benefit Plan, Funded Status of Plan
$ 567 1
$ 710 1
Defined Benefit Plan Assumptions Used Calculating Benefit Obligation, Change in Discount Rate
0.50% 
 
Number of high-quality corporate bonds
700 
 
Defined benefit plan, estimated future employer contributions during the next five years
280 
 
Amortization basis, straight line, in years
10 years 
 
Pension Benefits
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
Defined Benefit Plan, Funded Status of Plan
(544)1
(616)1
Assumptions used calculating net periodic benefit cost, expected long-term return on assets in future years
7.00% 
 
Postretirement Benefits
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
Defined Benefit Plan, Funded Status of Plan
(23)1
(94)1
Assumptions used calculating net periodic benefit cost, expected long-term return on assets in future years
7.00% 
 
Minimum
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
Defined benefit plan, estimated future employer contributions during the next five years
40 
 
Maximum
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
Defined benefit plan, estimated future employer contributions during the next five years
70 
 
Private equity
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
Number of limited partnerships in private equity funds
8 
 
Minimum invested capital within limited partnership investments
1 
 
Maximum invested capital within limited partnership investments
$ 4 
 
Union Electric Company |
Pension Benefits
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
Future funding requirement, percentage
40.00% 
 
Ameren Illinois Company |
Pension Benefits
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
Future funding requirement, percentage
50.00% 
 
Retirement Benefits (Summary Of Benefit Liability Recorded) (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2015
Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
 
 
Benefit liability recorded on the balance sheet
$ 567 1
$ 710 1
Union Electric Company
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
Benefit liability recorded on the balance sheet
236 
277 
Ameren Illinois Company
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
Benefit liability recorded on the balance sheet
$ 219 
$ 278 
Retirement Benefits (Funded Status Of Benefit Plans And Amounts Included In Regulatory Assets And OCI) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Change in plan assets:
 
 
 
Funded status – deficiency
$ (567)1
$ (710)1
 
Amounts recognized in the balance sheet consist of:
 
 
 
Noncurrent liability
580 
705 
 
Net liability recognized
567 1
710 1
 
Pension Benefits
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Accumulated benefit obligation at end of year
3,995 1
4,176 1
 
Change in benefit obligation:
 
 
 
Net benefit obligation at beginning of year
4,410 1
3,900 1
 
Service cost
92 1 2
79 1 2
91 2
Interest cost
174 1 2
183 1 2
163 2
Actuarial (gain) loss
(256)1
462 1
 
Settlement
(2)1
 
 
Benefits paid
(221)1
(214)1
 
Net benefit obligation at end of year
4,197 1
4,410 1
3,900 1
Change in plan assets:
 
 
 
Fair value of plan assets at beginning of year
3,794 1
3,461 1
 
Actual return on plan assets
(29)1
448 1
 
Employer contributions
111 1
99 1
156 1
Settlement
(2)1
 
 
Benefits paid
(221)1
(214)1
 
Fair value of plan assets at end of year
3,653 1
3,794 1
3,461 1
Funded status – deficiency
544 1
616 1
 
Accrued benefit cost at December 31
544 1
616 1
 
Amounts recognized in the balance sheet consist of:
 
 
 
Current liability(d)
3 1 3
3 1 3
 
Noncurrent liability
541 1
613 1
 
Net liability recognized
544 1
616 1
 
Amounts recognized in regulatory assets consist of:
 
 
 
Net actuarial (gain) loss
395 1
452 1
 
Prior service cost (credit)
(5)1
(6)1
 
Amounts (pretax) recognized in accumulated OCI consist of:
 
 
 
Net actuarial (gain) loss
17 1
29 1
 
Prior service cost (credit)
 
0 1
 
Total
407 1
475 1
 
Postretirement Benefits
 
 
 
Change in benefit obligation:
 
 
 
Net benefit obligation at beginning of year
1,203 1
1,096 1
 
Service cost
24 1 2
19 1 2
22 2
Interest cost
48 1 2
50 1 2
46 2
Participant contributions
8 1
16 1
 
Actuarial (gain) loss
(133)1
84 1
 
Benefits paid
(56)1
(65)1
 
Federal subsidy on benefits paid
0 1
3 1
 
Net benefit obligation at end of year
1,094 1
1,203 1
1,096 1
Change in plan assets:
 
 
 
Fair value of plan assets at beginning of year
1,109 1
1,074 1
 
Actual return on plan assets
(8)1
75 1
 
Employer contributions
18 1
6 1
25 1
Federal subsidy on benefits paid
0 1
3 1
 
Participant contributions
8 1
16 1
 
Benefits paid
(56)1
(65)1
 
Fair value of plan assets at end of year
1,071 1
1,109 1
1,074 1
Funded status – deficiency
23 1
94 1
 
Accrued benefit cost at December 31
23 1
94 1
 
Amounts recognized in the balance sheet consist of:
 
 
 
Noncurrent asset
(18)1 4
 
 
Current liability(d)
2 1 3
2 1 3
 
Noncurrent liability
39 1
92 1
 
Net liability recognized
23 1
94 1
 
Amounts recognized in regulatory assets consist of:
 
 
 
Net actuarial (gain) loss
(82)1
(7)1
 
Prior service cost (credit)
(11)1
(16)1
 
Amounts (pretax) recognized in accumulated OCI consist of:
 
 
 
Net actuarial (gain) loss
(3)1
(5)1
 
Prior service cost (credit)
0 1
(1)1
 
Total
$ (96)1
$ (29)1
 
Retirement Benefits (Assumptions Used To Determine Benefit Obligations) (Details)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Pension Benefits
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
Discount rate at measurement date
4.50% 
4.00% 
Increase in future compensation
3.50% 
3.50% 
Postretirement Benefits
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
Discount rate at measurement date
4.50% 
4.00% 
Increase in future compensation
3.50% 
3.50% 
Medical cost trend rate (initial)
5.00% 
5.00% 
Medical cost trend rate (ultimate)
5.00% 
5.00% 
Retirement Benefits (Cash Contributions Made To Benefit Plans) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Pension Benefits
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Cash contributions to benefit plans
$ 111 1
$ 99 1
$ 156 1
Postretirement Benefits
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Cash contributions to benefit plans
18 1
6 1
25 1
Union Electric Company |
Pension Benefits
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Cash contributions to benefit plans
47 
41 
60 
Union Electric Company |
Postretirement Benefits
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Cash contributions to benefit plans
8 
3 
10 
Ameren Illinois Company |
Pension Benefits
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Cash contributions to benefit plans
45 
39 
50 
Ameren Illinois Company |
Postretirement Benefits
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Cash contributions to benefit plans
8 
2 
11 
Other |
Pension Benefits
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Cash contributions to benefit plans
19 
19 
46 
Other |
Postretirement Benefits
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Cash contributions to benefit plans
$ 2 
$ 1 
$ 4 
Retirement Benefits (Target Allocation Of The Plans' Asset Categories) (Details)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Pension Benefits
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
Defined Benefit Plan, Actual Plan Asset Allocations
100.00% 
100.00% 
Pension Benefits |
Cash And Cash Equivalents
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
Minimum Target Allocation
0.00% 
 
Maximum Target Allocation
5.00% 
 
Defined Benefit Plan, Actual Plan Asset Allocations
1.00% 
2.00% 
Pension Benefits |
Equity Securities
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
Minimum Target Allocation
51.00% 
 
Maximum Target Allocation
61.00% 
 
Defined Benefit Plan, Actual Plan Asset Allocations
54.00% 
53.00% 
Pension Benefits |
U.S. large capitalization
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
Minimum Target Allocation
29.00% 
 
Maximum Target Allocation
39.00% 
 
Defined Benefit Plan, Actual Plan Asset Allocations
34.00% 
34.00% 
Pension Benefits |
U.S. small and mid-capitalization
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
Minimum Target Allocation
3.00% 
 
Maximum Target Allocation
13.00% 
 
Defined Benefit Plan, Actual Plan Asset Allocations
7.00% 
7.00% 
Pension Benefits |
International and emerging markets
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
Minimum Target Allocation
9.00% 
 
Maximum Target Allocation
19.00% 
 
Defined Benefit Plan, Actual Plan Asset Allocations
13.00% 
12.00% 
Pension Benefits |
Debt Securities
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
Minimum Target Allocation
35.00% 
 
Maximum Target Allocation
45.00% 
 
Defined Benefit Plan, Actual Plan Asset Allocations
40.00% 
41.00% 
Pension Benefits |
Real estate
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
Minimum Target Allocation
0.00% 
 
Maximum Target Allocation
9.00% 
 
Defined Benefit Plan, Actual Plan Asset Allocations
5.00% 
4.00% 
Pension Benefits |
Private equity
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
Minimum Target Allocation
0.00% 
 
Maximum Target Allocation
5.00% 
 
Defined Benefit Plan, Actual Plan Asset Allocations
1.00% 1
1.00% 1
Postretirement Benefits
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
Defined Benefit Plan, Actual Plan Asset Allocations
100.00% 
100.00% 
Postretirement Benefits |
Cash And Cash Equivalents
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
Minimum Target Allocation
0.00% 
 
Maximum Target Allocation
7.00% 
 
Defined Benefit Plan, Actual Plan Asset Allocations
4.00% 
4.00% 
Postretirement Benefits |
Equity Securities
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
Minimum Target Allocation
55.00% 
 
Maximum Target Allocation
65.00% 
 
Defined Benefit Plan, Actual Plan Asset Allocations
59.00% 
60.00% 
Postretirement Benefits |
U.S. large capitalization
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
Minimum Target Allocation
34.00% 
 
Maximum Target Allocation
44.00% 
 
Defined Benefit Plan, Actual Plan Asset Allocations
39.00% 
40.00% 
Postretirement Benefits |
U.S. small and mid-capitalization
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
Minimum Target Allocation
2.00% 
 
Maximum Target Allocation
12.00% 
 
Defined Benefit Plan, Actual Plan Asset Allocations
7.00% 
7.00% 
Postretirement Benefits |
International
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
Minimum Target Allocation
9.00% 
 
Maximum Target Allocation
19.00% 
 
Defined Benefit Plan, Actual Plan Asset Allocations
13.00% 
13.00% 
Postretirement Benefits |
Debt Securities
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
Minimum Target Allocation
33.00% 
 
Maximum Target Allocation
43.00% 
 
Defined Benefit Plan, Actual Plan Asset Allocations
37.00% 
36.00% 
Retirement Benefits (Fair Value Of Plan Assets Utilizing Fair Value Hierarchy) (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Real estate
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
$ 168 
$ 147 
$ 131 
Private equity
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
8 
13 
15 
Pension Benefits
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
3,653 1
3,794 1
3,461 1
Pension Benefits |
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
396 
411 
 
Pension Benefits |
Significant Other Observable Inputs (Level 2)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
3,176 
3,327 
 
Pension Benefits |
Significant Other Unobservable Inputs (Level 3)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
176 
160 
 
Pension Benefits |
Cash And Cash Equivalents
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
20 
38 
 
Pension Benefits |
Cash And Cash Equivalents |
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
0 
0 
 
Pension Benefits |
Cash And Cash Equivalents |
Significant Other Observable Inputs (Level 2)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
20 
38 
 
Pension Benefits |
U.S. large capitalization
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
1,296 
1,331 
 
Pension Benefits |
U.S. large capitalization |
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
0 
0 
 
Pension Benefits |
U.S. large capitalization |
Significant Other Observable Inputs (Level 2)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
1,296 
1,331 
 
Pension Benefits |
U.S. small and mid-capitalization
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
268 
270 
 
Pension Benefits |
U.S. small and mid-capitalization |
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
268 
270 
 
Pension Benefits |
U.S. small and mid-capitalization |
Significant Other Observable Inputs (Level 2)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
0 
0 
 
Pension Benefits |
International and emerging markets
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
491 
494 
 
Pension Benefits |
International and emerging markets |
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
122 
134 
 
Pension Benefits |
International and emerging markets |
Significant Other Observable Inputs (Level 2)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
369 
360 
 
Pension Benefits |
Corporate Bonds
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
631 
1,026 
 
Pension Benefits |
Corporate Bonds |
Significant Other Observable Inputs (Level 2)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
631 
1,026 
 
Pension Benefits |
Municipal Bonds
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
104 
175 
 
Pension Benefits |
Municipal Bonds |
Significant Other Observable Inputs (Level 2)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
104 
175 
 
Pension Benefits |
U.S. treasury and agency securities
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
757 
372 
 
Pension Benefits |
U.S. treasury and agency securities |
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
6 
6 
 
Pension Benefits |
U.S. treasury and agency securities |
Significant Other Observable Inputs (Level 2)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
751 
366 
 
Pension Benefits |
Other
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
5 
31 
 
Pension Benefits |
Other |
Significant Other Observable Inputs (Level 2)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
5 
31 
 
Pension Benefits |
Real estate
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
168 
147 
 
Pension Benefits |
Real estate |
Significant Other Unobservable Inputs (Level 3)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
168 
147 
 
Pension Benefits |
Private equity
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
8 
13 
 
Pension Benefits |
Private equity |
Significant Other Unobservable Inputs (Level 3)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
8 
13 
 
Pension Benefits |
Derivative assets
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
 
1 
 
Pension Benefits |
Derivative assets |
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
 
1 
 
Pension Benefits |
Medical benefit assets
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
(123)2
(125)2
 
Pension Benefits |
Net receivables
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
28 3
21 3
 
Pension Benefits |
Includes Medical Benefit Component Under Section401 H And Excludes Receivables Related To Pending Security Sales [Member]
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
3,748 
3,898 
 
Pension Benefits |
Excludes Medical Benefit Component Under Section401 H And Includes Receivables Related To Pending Security Sales [Member]
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
3,653 
3,794 
 
Postretirement Benefits
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
1,071 1
1,109 1
1,074 1
Postretirement Benefits |
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
431 
487 
 
Postretirement Benefits |
Significant Other Observable Inputs (Level 2)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
545 
551 
 
Postretirement Benefits |
Cash And Cash Equivalents
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
61 
89 
 
Postretirement Benefits |
Cash And Cash Equivalents |
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
61 
89 
 
Postretirement Benefits |
Cash And Cash Equivalents |
Significant Other Observable Inputs (Level 2)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
0 
0 
 
Postretirement Benefits |
U.S. large capitalization
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
370 
392 
 
Postretirement Benefits |
U.S. large capitalization |
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
272 
291 
 
Postretirement Benefits |
U.S. large capitalization |
Significant Other Observable Inputs (Level 2)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
98 
101 
 
Postretirement Benefits |
U.S. small and mid-capitalization
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
65 
70 
 
Postretirement Benefits |
U.S. small and mid-capitalization |
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
65 
70 
 
Postretirement Benefits |
International
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
126 
131 
 
Postretirement Benefits |
International |
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
33 
37 
 
Postretirement Benefits |
International |
Significant Other Observable Inputs (Level 2)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
93 
94 
 
Postretirement Benefits |
Other Equity
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
7 
7 
 
Postretirement Benefits |
Other Equity |
Significant Other Observable Inputs (Level 2)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
7 
7 
 
Postretirement Benefits |
Corporate Bonds
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
138 
105 
 
Postretirement Benefits |
Corporate Bonds |
Significant Other Observable Inputs (Level 2)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
138 
105 
 
Postretirement Benefits |
Municipal Bonds
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
114 
111 
 
Postretirement Benefits |
Municipal Bonds |
Significant Other Observable Inputs (Level 2)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
114 
111 
 
Postretirement Benefits |
U.S. treasury and agency securities
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
55 
89 
 
Postretirement Benefits |
U.S. treasury and agency securities |
Significant Other Observable Inputs (Level 2)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
55 
89 
 
Postretirement Benefits |
Other
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
40 
44 
 
Postretirement Benefits |
Other |
Significant Other Observable Inputs (Level 2)
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
40 
44 
 
Postretirement Benefits |
Medical benefit assets
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
123 2
125 2
 
Postretirement Benefits |
Net payables
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
(28)4
(54)4
 
Postretirement Benefits |
Excludes Medical Benefit Component Under Section401 H And Excludes Payables Related To Pending Security Sales [Member]
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
976 
1,038 
 
Postretirement Benefits |
Includes Medical Benefit Component Under Section401 H And Excludes Payables Related To Pending Security Sales [Member]
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Fair value of plan assets
$ 1,071 
$ 1,109 
 
Retirement Benefits (Changes In The Fair Value Of Plan Assets Classified As Level 3) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Real estate
 
 
Change in plan assets:
 
 
Fair value of plan assets at beginning of year
$ 147 
$ 131 
Actual Return on Plan Assets Related to Assets Still Held at the Reporting Date
14 
11 
Purchases, Sales and Settlements, net
7 
5 
Fair value of plan assets at end of year
168 
147 
Private equity
 
 
Change in plan assets:
 
 
Fair value of plan assets at beginning of year
13 
15 
Actual Return on Plan Assets Related to Assets Still Held at the Reporting Date
(9)
(9)
Actual Return on Plan Assets Related to Assets Sold During the Period
9 
10 
Purchases, Sales and Settlements, net
(5)
(3)
Fair value of plan assets at end of year
$ 8 
$ 13 
Retirement Benefits (Components Of Net Periodic Benefit Cost) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Pension Benefits
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Service cost
$ 92 1 2
$ 79 1 2
$ 91 1
Interest cost
174 1 2
183 1 2
163 1
Expected return on plan assets
(248)1
(229)1
(218)1
Prior service credit
(1)1
(1)1
(2)1
Actuarial loss
74 1
49 1
87 1
Curtailment
 
 
(12)1
Settlement Loss
1 1
 
 
Net periodic benefit cost
92 1
81 1
109 1 3
Postretirement Benefits
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Service cost
24 1 2
19 1 2
22 1
Interest cost
48 1 2
50 1 2
46 1
Expected return on plan assets
(68)1
(65)1
(62)1
Prior service credit
(5)1
(5)1
(6)1
Actuarial loss
5 1
(7)1
8 1
Curtailment
 
 
(7)1
Settlement Loss
 
0 1
 
Net periodic benefit cost
4 1
(8)1
1 1 3
New Ameren Energy Resources Company, LLC |
Pension Benefits
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Net periodic benefit cost
 
 
6 1 3
New Ameren Energy Resources Company, LLC |
Postretirement Benefits
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Net periodic benefit cost
 
 
$ 7 1 3
Retirement Benefits (Summary Of Estimated Amortizable Amounts From Regulatory Assets and Accumulated OCI Into Net Periodic Benefit Cost) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Pension Benefits
 
Defined Benefit Plan Disclosure [Line Items]
 
Prior service credit
$ (1)1
Net actuarial loss
46 1
Net actuarial (gain) loss
(3)1
Net periodic benefit cost
42 1
Postretirement Benefits
 
Defined Benefit Plan Disclosure [Line Items]
 
Prior service credit
(4)1
Net actuarial loss
(3)1
Net actuarial (gain) loss
(2)1
Net periodic benefit cost
$ (9)1
Retirement Benefits (Summary Of Benefit Plan Costs Incurred) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Pension Benefits
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Net periodic benefit cost
$ 92 1
$ 81 1
$ 109 1 2
Postretirement Benefits
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Net periodic benefit cost
4 1
(8)1
1 1 2
Union Electric Company |
Pension Benefits
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Net periodic benefit cost
54 3
50 3
69 3
Union Electric Company |
Postretirement Benefits
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Net periodic benefit cost
8 3
3 3
8 3
Ameren Illinois Company |
Pension Benefits
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Net periodic benefit cost
38 
30 
41 
Ameren Illinois Company |
Postretirement Benefits
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Net periodic benefit cost
(3)
(9)
0 
Other |
Pension Benefits
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Net periodic benefit cost
0 
1 
5 
Other |
Postretirement Benefits
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Net periodic benefit cost
(1)
(2)
0 
Parent Company |
Pension Benefits
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Net periodic benefit cost
92 4
81 4
115 4
Parent Company |
Postretirement Benefits
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Net periodic benefit cost
$ 4 4
$ (8)4
$ 8 4
Retirement Benefits (Schedule Of Expected Payments From Qualified Trust And Company Funds) (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2015
Pension Benefits |
Paid From Qualified Trust
 
Defined Benefit Plan Disclosure [Line Items]
 
2016
$ 233 
2017
244 
2018
250 
2019
257 
2020
261 
2021 - 2025
1,377 
Pension Benefits |
Paid From Company Funds
 
Defined Benefit Plan Disclosure [Line Items]
 
2016
3 
2017
3 
2018
3 
2019
3 
2020
3 
2021 - 2025
13 
Postretirement Benefits |
Paid From Qualified Trust
 
Defined Benefit Plan Disclosure [Line Items]
 
2016
55 
2017
58 
2018
60 
2019
62 
2020
65 
2021 - 2025
341 
Postretirement Benefits |
Paid From Company Funds
 
Defined Benefit Plan Disclosure [Line Items]
 
2016
2 
2017
2 
2018
2 
2019
2 
2020
2 
2021 - 2025
$ 12 
Retirement Benefits (Assumptions Used To Determine Net Periodic Benefit Cost) (Details)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Pension Benefits
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Discount rate at measurement date
4.00% 
4.75% 
4.00% 
Expected return on plan assets
7.25% 
7.25% 
7.50% 
Increase in future compensation
3.50% 
3.50% 
3.50% 
Postretirement Benefits
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Discount rate at measurement date
4.00% 
4.75% 
4.00% 
Expected return on plan assets
7.00% 
7.00% 
7.25% 
Increase in future compensation
3.50% 
3.50% 
3.50% 
Medical cost trend rate (initial)
5.00% 
5.00% 
5.00% 
Medical cost trend rate (ultimate)
5.00% 
5.00% 
5.00% 
Retirement Benefits (Schedule Of Potential Changes In Key Assumptions) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Pension Benefits
 
Defined Benefit Plan Disclosure [Line Items]
 
Service Cost and Interest Cost, .25% decrease in discount rate
$ (1)
Benefit Obligation, .25% decrease in discount rate
130 
Service Cost and Interest Cost, .25% increase in salary rate
2 
Benefit Obligation, .25% increase in salary rate
14 
Postretirement Benefits
 
Defined Benefit Plan Disclosure [Line Items]
 
Service Cost and Interest Cost, .25% decrease in discount rate
1 
Benefit Obligation, .25% decrease in discount rate
37 
Service Cost and Interest Cost, 1.00% increase in annual medical trend
3 
Benefit Obligation, 1.00% increase in annual medical trend
44 
Service Cost and Interest Cost, 1.00% decrease in annual medical trend
(3)
Benefit Obligation, 1.00% decrease in annual medical trend
$ (44)
Retirement Benefits (Schedule Of Matching Contributions) (Details) (401 (K), USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Employer contributions
$ 29 1
$ 28 1
$ 27 1
Union Electric Company
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Employer contributions
16 
16 
16 
Ameren Illinois Company
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Employer contributions
12 
11 
10 
Other
 
 
 
Defined Benefit Plan Disclosure [Line Items]
 
 
 
Employer contributions
$ 1 
$ 1 
$ 1 
Stock-Based Compensation (Narrative) (Details) (USD $)
In Millions, except Share data, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
 
 
 
Maximum shares available for grants
8,000,000 
 
 
Share-based compensation expense
$ 19 
$ 19 
$ 20 
Employee service share-based compensation, tax benefit from compensation expense
7 
7 
8 
Amounts paid to settle share units
27 
33 
11 
Compensation cost not yet recognized
$ 21 
 
 
Expected weighted average recognition period for share-based compensation expense, in months
23 months 
 
 
Performance Share Units
 
 
 
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
 
 
 
Performance period
3 years 
 
 
Percentage of shares issued per share unit, minimum
0.00% 
 
 
Percentage of shares issued per share unit, maximum
200.00% 
 
 
Fair value of each share unit, per share
$ 52.88 1
$ 38.90 
 
Closing common share price
 
$ 46.13 
$ 36.16 
Three-year risk-free rate
1.10% 
0.78% 
 
Volatility rate, minimum
12.00% 
12.00% 
 
Volatility rate, maximum
18.00% 
18.00% 
 
Stock-Based Compensation (Summary Of Nonvested Shares) (Details) (Performance Share Units, USD $)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Performance Share Units
 
 
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
 
 
Share Units, Nonvested at beginning of year
1,162,377 
 
Share Units, Granted
570,313 1
 
Share Units, Unearned or forfeited
(1,944)
 
Share Units, Earned and vested
(705,876)2
 
Share Units, Nonvested at end of year
1,024,870 
1,162,377 
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
 
 
Weighted-average Fair Value per Unit, Nonvested at beginning of year
$ 35.35 
 
Weighted-averageFair Value per Unit, granted
$ 52.88 1
$ 38.90 
Weighted-average Fair Value per Unit, Unearned or forfeited
$ 34.75 
 
Weighted-average Fair Value per Unit, Earned and vested
$ 33.93 2
 
Weighted-average Fair Value per Unit, Nonvested at end of year
$ 46.08 
$ 35.35 
Three-year risk-free rate
1.10% 
0.78% 
Volatility rate, minimum
12.00% 
12.00% 
Volatility rate, maximum
18.00% 
18.00% 
Income Taxes (Schedule Of Effective Income Tax Rate Reconciliation) (Details)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Income Taxes [Line Items]
 
 
 
Statutory federal income tax rate:
35.00% 
35.00% 
35.00% 
Depreciation differences
(1.00%)
 
 
Amortization of investment tax credit
(1.00%)
(1.00%)
(1.00%)
State tax
5.00% 
4.00% 
4.00% 
Other permanent items
 
1.00% 
0.00% 
Effective income tax rate
38.00% 
39.00% 
38.00% 
Union Electric Company
 
 
 
Income Taxes [Line Items]
 
 
 
Statutory federal income tax rate:
35.00% 
35.00% 
35.00% 
Depreciation differences
0.00% 
 
0.00% 
Amortization of investment tax credit
(1.00%)
(1.00%)
(1.00%)
State tax
3.00% 
3.00% 
3.00% 
Other permanent items
0.00% 
0.00% 
1.00% 
Effective income tax rate
37.00% 
37.00% 
38.00% 
Ameren Illinois Company
 
 
 
Income Taxes [Line Items]
 
 
 
Statutory federal income tax rate:
35.00% 
35.00% 
35.00% 
Depreciation differences
(2.00%)
 
(1.00%)
Amortization of investment tax credit
0.00% 
0.00% 
0.00% 
State tax
5.00% 
6.00% 
6.00% 
Other permanent items
(1.00%)
 
 
Effective income tax rate
37.00% 
41.00% 
40.00% 
Income Taxes (Schedule Of Components Of Income Tax Expense (Benefit)) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Income Taxes [Line Items]
 
 
 
Current Federal taxes
$ (2)
$ (37)
$ (118)
Current State taxes
(4)
(37)
19 
Deferred Federal taxes
299 
369 
368 
Deferred State taxes
76 
88 
48 
Deferred investment tax credits, amortization
(6)
(6)
(6)
Total income tax expense
363 
377 
311 
Union Electric Company
 
 
 
Income Taxes [Line Items]
 
 
 
Current Federal taxes
110 
(13)
136 
Current State taxes
17 
(3)
41 
Deferred Federal taxes
71 
222 
64 
Deferred State taxes
16 
28 
6 
Deferred investment tax credits, amortization
(5)
(5)
(5)
Total income tax expense
209 
229 
242 
Ameren Illinois Company
 
 
 
Income Taxes [Line Items]
 
 
 
Current Federal taxes
(83)
(51)
(15)
Current State taxes
(11)
(2)
21 
Deferred Federal taxes
193 
159 
99 
Deferred State taxes
29 
38 
6 
Deferred investment tax credits, amortization
(1)
(1)
(1)
Total income tax expense
127 
143 
110 
Other
 
 
 
Income Taxes [Line Items]
 
 
 
Current Federal taxes
(29)
27 
(239)1
Current State taxes
(10)
(32)
(43)1
Deferred Federal taxes
35 
(12)
205 1
Deferred State taxes
31 
22 
36 1
Deferred investment tax credits, amortization
0 
0 
0 
Total income tax expense
$ 27 
$ 5 
$ (41)
Income Taxes (Schedule Of Deferred Tax Assets And Liabilities Resulting From Temporary Differences) (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2015
Dec. 31, 2014
Income Taxes [Line Items]
 
 
Plant related
$ 4,555 
$ 4,185 
Regulatory assets, net
80 
78 
Deferred benefit costs
(207)
(220)
Revenue Requirement Reconciliation Adjustment
66 
69 
ARO
(603)
(675)
Other
 
134 
Other
(6)
 
Total net accumulated deferred income tax liabilities
3,885 1
3,571 1
Union Electric Company
 
 
Income Taxes [Line Items]
 
 
Plant related
2,931 
2,776 
Regulatory assets, net
81 
82 
Deferred benefit costs
(76)
(80)
ARO
(65)
(107)
Other
 
86 
Other
(27)
 
Total net accumulated deferred income tax liabilities
2,844 1
2,757 1
Ameren Illinois Company
 
 
Income Taxes [Line Items]
 
 
Plant related
1,587 
1,393 
Regulatory assets, net
(1)
(5)
Deferred benefit costs
(40)
(45)
Revenue Requirement Reconciliation Adjustment
66 
66 
ARO
(133)
(139)
Other
1 
 
Other
 
(22)
Total net accumulated deferred income tax liabilities
1,480 1
1,248 1
Other
 
 
Income Taxes [Line Items]
 
 
Plant related
37 
16 
Regulatory assets, net
 
1 
Deferred benefit costs
(91)
(95)
Revenue Requirement Reconciliation Adjustment
0 
3 
ARO
(405)
(429)
Other
20 
70 
Total net accumulated deferred income tax liabilities
$ (439)1
$ (434)1
Income Taxes (Schedule Of Net Operating Loss Carryforwards And Tax Credit Carryforwards) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Operating Loss Carryforwards [Line Items]
 
 
Net operating loss carryforwards
$ 453 
$ 531 
Tax credit carryforwards
144 
131 
Tax credit carryforward, expiration period start
Jan. 01, 2016 
Jan. 01, 2013 
Deferred Tax Assets, Charitable Contribution Carryforwards
10 1
19 2
Deferred Tax Assets, Valuation Allowance, Noncurrent
(4)3
6 3
Deferred Tax Assets, Net of Valuation Allowance, Noncurrent
6 
13 
Federal
 
 
Operating Loss Carryforwards [Line Items]
 
 
Net operating loss carryforwards
407 4
457 5
Tax credit carryforwards
105 6
99 6
Net operating loss carryforward, expiration period start
Jan. 01, 2029 
Jan. 01, 2028 
Tax credit carryforward, expiration period start
Jan. 01, 2029 
Jan. 01, 2029 
State
 
 
Operating Loss Carryforwards [Line Items]
 
 
Net operating loss carryforwards
46 7
74 8
Tax credit carryforwards
41 9
36 10
Tax Credit Carryforward, Valuation Allowance
(2)3
4 3
Net operating loss carryforward, expiration period start
Jan. 01, 2023 
Jan. 01, 2019 
Tax credit carryforward, expiration period start
Jan. 01, 2016 
Jan. 01, 2013 
Union Electric Company
 
 
Operating Loss Carryforwards [Line Items]
 
 
Net operating loss carryforwards
39 
86 
Tax credit carryforwards
26 
21 
Union Electric Company |
Federal
 
 
Operating Loss Carryforwards [Line Items]
 
 
Net operating loss carryforwards
35 4
75 5
Tax credit carryforwards
26 6
21 6
Union Electric Company |
State
 
 
Operating Loss Carryforwards [Line Items]
 
 
Net operating loss carryforwards
4 7
11 8
Tax credit carryforwards
0 9
1 10
Tax Credit Carryforward, Valuation Allowance
0 3
(1)3
Ameren Illinois Company
 
 
Operating Loss Carryforwards [Line Items]
 
 
Net operating loss carryforwards
131 
137 
Tax credit carryforwards
2 
2 
Ameren Illinois Company |
Federal
 
 
Operating Loss Carryforwards [Line Items]
 
 
Net operating loss carryforwards
127 4
127 5
Tax credit carryforwards
1 6
1 6
Ameren Illinois Company |
State
 
 
Operating Loss Carryforwards [Line Items]
 
 
Net operating loss carryforwards
4 7
10 8
Tax credit carryforwards
1 9
2 10
Tax Credit Carryforward, Valuation Allowance
0 3
(1)3
Other
 
 
Operating Loss Carryforwards [Line Items]
 
 
Net operating loss carryforwards
283 
308 
Tax credit carryforwards
116 
108 
Deferred Tax Assets, Charitable Contribution Carryforwards
10 1
19 2
Deferred Tax Assets, Valuation Allowance, Noncurrent
(4)3
(6)3
Deferred Tax Assets, Net of Valuation Allowance, Noncurrent
6 
13 
Other |
Federal
 
 
Operating Loss Carryforwards [Line Items]
 
 
Net operating loss carryforwards
245 4
255 5
Tax credit carryforwards
78 6
77 6
Other |
State
 
 
Operating Loss Carryforwards [Line Items]
 
 
Net operating loss carryforwards
38 7
53 8
Tax credit carryforwards
40 9
33 10
Tax Credit Carryforward, Valuation Allowance
$ (2)3
$ (2)3
Income Taxes (Reconciliation Of The Change In The Liability For Interest On Unrecognized Tax Benefits) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Income Tax Contingency [Line Items]
 
 
 
Liability for interest
 
$ 1 
$ 6 
Interest charges (income)
 
(1)
(5)
Liability for interest
0 
0 
1 
Union Electric Company
 
 
 
Income Tax Contingency [Line Items]
 
 
 
Liability for interest
0 
0 
8 
Interest charges (income)
0 
0 
(8)
Liability for interest
0 
0 
0 
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities
 
0 
 
Ameren Illinois Company
 
 
 
Income Tax Contingency [Line Items]
 
 
 
Liability for interest
 
0 
1 
Interest charges (income)
 
0 
(1)
Liability for interest
0 
0 
0 
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities
 
0 
 
Other
 
 
 
Income Tax Contingency [Line Items]
 
 
 
Liability for interest
 
1 
(3)
Interest charges (income)
 
(1)
4 
Liability for interest
0 
0 
1 
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities
 
0 
 
2007 through 2011 tax year |
Ameren Corporation [Member]
 
 
 
Income Tax Contingency [Line Items]
 
 
 
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities
 
20 
 
2007 through 2011 tax year |
Union Electric Company
 
 
 
Income Tax Contingency [Line Items]
 
 
 
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities
 
13 
 
Tax Year 2012 [Member] |
Union Electric Company
 
 
 
Income Tax Contingency [Line Items]
 
 
 
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities
 
$ 18 
 
Income Taxes (Narrative) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended 1 Months Ended 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Jan. 31, 2011
Maximum
Illinois Corporate Income Tax
Dec. 31, 2015
Union Electric Company
Dec. 31, 2014
Union Electric Company
Dec. 31, 2013
Union Electric Company
Dec. 31, 2015
Ameren Illinois Company
Dec. 31, 2014
Ameren Illinois Company
Dec. 31, 2013
Ameren Illinois Company
Dec. 31, 2015
Income Tax Rate in 2015
Illinois Corporate Income Tax
Dec. 31, 2015
Income Tax Rate in 2025
Illinois Corporate Income Tax
Dec. 31, 2015
State
Dec. 31, 2014
State
Income Taxes [Line Items]
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities
 
 
 
 
 
$ 0 
 
 
$ 0 
 
 
 
$ 53 
$ 2 
State corporate income tax rate
5.00% 
4.00% 
4.00% 
9.50% 
3.00% 
3.00% 
3.00% 
5.00% 
6.00% 
6.00% 
7.75% 
7.30% 
 
 
Unrecognized Tax Benefits, Decrease Resulting from Current Period Tax Positions
 
 
$ 103 
 
 
 
$ 95 
 
 
$ 5 
 
 
 
 
Related Party Transactions (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Union Electric Company
 
 
 
Related Party Transaction [Line Items]
 
 
 
Operating Revenues
$ 42 
$ 27 
$ 25 
Operating Expenses
131 
124 
116 
Union Electric Company |
Ameren Missouri Power Supply Agreements with Ameren Illinois
 
 
 
Related Party Transaction [Line Items]
 
 
 
Operating Revenues
15 
5 
3 
Union Electric Company |
Ameren Missouri and Ameren Illinois Rent and Facility Services
 
 
 
Related Party Transaction [Line Items]
 
 
 
Operating Revenues
25 
21 
21 
Union Electric Company |
Ameren Missouri and Ameren Illinois miscellaneous support services
 
 
 
Related Party Transaction [Line Items]
 
 
 
Operating Revenues
2 
1 
1 
Union Electric Company |
Ameren Services Support Services Agreement
 
 
 
Related Party Transaction [Line Items]
 
 
 
Operating Expenses
131 
124 
116 
Union Electric Company |
Money Pool
 
 
 
Related Party Transaction [Line Items]
 
 
 
Interest (Charges) Income
1 1
1 1
1 1
Ameren Illinois Company
 
 
 
Related Party Transaction [Line Items]
 
 
 
Operating Revenues
4 
2 
4 
Operating Expenses
119 
109 
93 
Ameren Illinois Company |
Ameren Missouri and Ameren Illinois Rent and Facility Services
 
 
 
Related Party Transaction [Line Items]
 
 
 
Operating Revenues
4 
2 
1 
Ameren Illinois Company |
Ameren Missouri and Ameren Illinois miscellaneous support services
 
 
 
Related Party Transaction [Line Items]
 
 
 
Operating Revenues
1 1
1 1
3 
Ameren Illinois Company |
Ameren Illinois Power Supply Agreements with Ameren Missouri
 
 
 
Related Party Transaction [Line Items]
 
 
 
Operating Expenses
15 
5 
3 
Ameren Illinois Company |
Ameren Illinois transmission agreements with ATXI
 
 
 
Related Party Transaction [Line Items]
 
 
 
Operating Expenses
2 
2 
2 
Ameren Illinois Company |
Purchased Power
 
 
 
Related Party Transaction [Line Items]
 
 
 
Operating Expenses
17 
7 
5 
Ameren Illinois Company |
Ameren Services Support Services Agreement
 
 
 
Related Party Transaction [Line Items]
 
 
 
Operating Expenses
119 
109 
93 
Ameren Illinois Company |
Money Pool
 
 
 
Related Party Transaction [Line Items]
 
 
 
Interest (Charges) Income
$ 1 1
$ 1 1
$ 1 1
Related Party Transactions (Narrative) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended 1 Months Ended 12 Months Ended 1 Months Ended 12 Months Ended 3 Months Ended
Dec. 31, 2015
Union Electric Company
Dec. 31, 2014
Union Electric Company
Dec. 31, 2013
Union Electric Company
Apr. 30, 2012
Period Five
Union Electric Company
May 31, 2011
Period Five
Ameren Illinois Company
Union Electric Company
MWh
Apr. 30, 2012
Period Six
Union Electric Company
Dec. 31, 2015
Period Seven [Member]
Union Electric Company
Apr. 30, 2010
Period Four
Union Electric Company
May 31, 2011
Period Four
Ameren Illinois Company
Union Electric Company
MWh
Dec. 31, 2015
Ameren Illinois Power Supply Agreements with Ameren Missouri
Ameren Illinois Company
MWh
Dec. 31, 2015
April 2015 Procurement [Member]
Ameren Illinois Power Supply Agreements with Ameren Missouri
Ameren Illinois Company
MWh
Dec. 31, 2015
September 2015 Procurement [Member]
Ameren Illinois Power Supply Agreements with Ameren Missouri
Ameren Illinois Company
MWh
Related Party Transaction [Line Items]
 
 
 
 
 
 
 
 
 
 
 
 
Energy Supply Agreements Amount
 
 
 
$ 1 
 
$ 3 
$ 15 
$ 1 
 
 
 
 
Long-term Contract for Purchase of Electric Power, Related Party Contract, Fixed Power
 
 
 
 
40,800 
 
 
 
40,800 
168,400 
667,000 
339,000 
Long-term Contract for Purchase of Electric Power, Related Party Contract, Fixed Power, Rate
 
 
 
 
28 
 
 
 
29 
51 
36 
38 
Noncash Or Part Noncash Capital Contribution From Parent
$ 38 
$ 9 
$ 0 
 
 
 
 
 
 
 
 
 
Commitments And Contingencies (Callaway Nuclear Energy Center) (Details) (USD $)
12 Months Ended
Dec. 31, 2015
Commitments and Contingencies [Line Items]
 
Insurance aggregate maximum coverage
$ 13,489,000,000 1
Insurance maximum coverage per incident
127,000,000 
Threshold Amount For Retrospective Insurance Assessment For Covered Loss Under Public Liability And Nuclear Worker Liability Insurance Policy
375,000,000 
Annual payment in the event of an incident at any licensed commercial reactor
19,000,000 
Aggregate maximum assessment per incident under Price-Anderson liability provisions of Atomic Energy Act
127,000,000 
Maximum annual payment to be paid in a calendar year per reactor incident under liability provisions of Atomic Energy Act
19,000,000 
Amount of coverage in excess of primary property liability coverage
2,250,000,000.00 
Amount of weekly indemnity coverage commencing eight weeks after power outage
4,500,000 
Number of weeks of coverage after the first eight weeks of an outage
1 year 
Amount of additional weekly indemnity coverage commencing after initial indemnity coverage
3,600,000 
Number of additional weeks after initial indemnity coverage for power outage, minimum
1 year 4 months 10 days 
Amount of weekly indemnity coverage thereafter not exceeding policy limit
490,000,000 
Aggregate nuclear power industry insurance policy limit for losses from terrorist attacks within twelve month period
3,240,000,000 
Public Liability And Nuclear Worker Liability - American Nuclear Insurers
 
Commitments and Contingencies [Line Items]
 
Insurance aggregate maximum coverage
375,000,000 
Insurance maximum coverage per incident
0 
Public Liability And Nuclear Worker Liability - Pool Participation
 
Commitments and Contingencies [Line Items]
 
Insurance aggregate maximum coverage
13,114,000,000 2
Insurance maximum coverage per incident
127,000,000 3
Property Damage - Nuclear Electric Insurance Ltd
 
Commitments and Contingencies [Line Items]
 
Insurance aggregate maximum coverage
2,750,000,000 4
Insurance maximum coverage per incident
27,000,000 5
Replacement Power - Nuclear Electric Insurance Ltd
 
Commitments and Contingencies [Line Items]
 
Insurance aggregate maximum coverage
490,000,000 6
Insurance maximum coverage per incident
10,000,000 5
Sub-limit of Amount of Weekly indemnity Coverage Thereafter Not Exceeding Policy Limit for Non-Nuclear Events
328,000,000 
Property Damage European Mutual Association for Nuclear Insurance
 
Commitments and Contingencies [Line Items]
 
Insurance aggregate maximum coverage
500,000,000 7
Amount of primary property liability coverage
500,000,000 
Radiation Event
 
Commitments and Contingencies [Line Items]
 
Insurance aggregate maximum coverage
500,000,000 
Property Damage
 
Commitments and Contingencies [Line Items]
 
Insurance aggregate maximum coverage
3,250,000,000 
Insurance maximum coverage per incident
27,000,000 
Non-radiation event
 
Commitments and Contingencies [Line Items]
 
Aggregate nuclear power industry insurance policy limit for losses from terrorist attacks within twelve month period
$ 1,830,000,000 
Commitments And Contingencies (Schedule Of Lease Obligations) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Commitments and Contingencies [Line Items]
 
 
 
Capital lease payments, due in one year
$ 33 1 2
 
 
Capital lease payments, due in two years
33 1 2
 
 
Capital lease payments, due in three years
32 1 2
 
 
Capital lease payments, due in four years
32 1 2
 
 
Capital lease payments, due in five years
32 1 2
 
 
Capital lease payments, After 5 Years
329 1 2
 
 
Capital lease payments, Total
491 1 2
 
 
Less Amount representing interest, due in one year
27 2
 
 
Less Amount representing interest, due in two years
27 2
 
 
Less Amount representing interest, due in three years
26 2
 
 
Less Amount representing interest, due in four years
25 2
 
 
Less Amount representing interest, due in 5 years
25 2
 
 
Less Amount representing interest, After 5 Years
73 2
 
 
Less Amount representing interest, Total
203 2
 
 
Present value of minimum capital lease payments, due in one year
6 2
 
 
Present value of minimum capital lease payments, due in two years
6 2
 
 
Present value of minimum capital lease payments, due in three years
6 2
 
 
Present value of minimum capital lease payments, due in four years
7 2
 
 
Present value of minimum capital lease payments, due in five years
7 2
 
 
Present value of minimum capital lease payments, After 5 Years
256 2
 
 
Present value of minimum capital lease payments, Total
288 2
 
 
Operating leases, due in one year
14 2 3
 
 
Operating leases, due in two years
13 2 3
 
 
Operating leases, due in three years
12 2 3
 
 
Operating leases, due in four years
12 2 3
 
 
Operating leases, due in five years
11 2 3
 
 
Operating leases, After 5 Years
30 2 3
 
 
Operating leases, Total
92 2 3
 
 
Total lease obligations, due in one year
20 2
 
 
Total lease obligations, due in two years
19 2
 
 
Total lease obligations, due in three years
18 2
 
 
Total lease obligations, due in four years
19 2
 
 
Total lease obligations, due in five years
18 2
 
 
Total lease obligations, After 5 Years
286 2
 
 
Total lease obligations, Total
380 2
 
 
Annual obligation for real estate leases and railroad licenses
3 
 
 
Total rental expense
36 4
37 4
32 4
Union Electric Company
 
 
 
Commitments and Contingencies [Line Items]
 
 
 
Capital lease payments, due in one year
33 1
 
 
Capital lease payments, due in two years
33 1
 
 
Capital lease payments, due in three years
32 1
 
 
Capital lease payments, due in four years
32 1
 
 
Capital lease payments, due in five years
32 1
 
 
Capital lease payments, After 5 Years
329 1
 
 
Capital lease payments, Total
491 1
 
 
Less Amount representing interest, due in one year
27 
 
 
Less Amount representing interest, due in two years
27 
 
 
Less Amount representing interest, due in three years
26 
 
 
Less Amount representing interest, due in four years
25 
 
 
Less Amount representing interest, due in 5 years
25 
 
 
Less Amount representing interest, After 5 Years
73 
 
 
Less Amount representing interest, Total
203 
 
 
Present value of minimum capital lease payments, due in one year
6 
 
 
Present value of minimum capital lease payments, due in two years
6 
 
 
Present value of minimum capital lease payments, due in three years
6 
 
 
Present value of minimum capital lease payments, due in four years
7 
 
 
Present value of minimum capital lease payments, due in five years
7 
 
 
Present value of minimum capital lease payments, After 5 Years
256 
 
 
Present value of minimum capital lease payments, Total
288 
 
 
Operating leases, due in one year
12 3
 
 
Operating leases, due in two years
11 3
 
 
Operating leases, due in three years
11 3
 
 
Operating leases, due in four years
11 3
 
 
Operating leases, due in five years
10 3
 
 
Operating leases, After 5 Years
29 3
 
 
Operating leases, Total
84 3
 
 
Total lease obligations, due in one year
18 
 
 
Total lease obligations, due in two years
17 
 
 
Total lease obligations, due in three years
17 
 
 
Total lease obligations, due in four years
18 
 
 
Total lease obligations, due in five years
17 
 
 
Total lease obligations, After 5 Years
285 
 
 
Total lease obligations, Total
372 
 
 
Annual obligation for real estate leases and railroad licenses
2 
 
 
Total rental expense
34 
32 
29 
Ameren Illinois Company
 
 
 
Commitments and Contingencies [Line Items]
 
 
 
Operating leases, due in one year
1 3
 
 
Operating leases, due in two years
1 3
 
 
Operating leases, due in three years
1 3
 
 
Operating leases, due in four years
1 3
 
 
Operating leases, due in five years
1 3
 
 
Operating leases, After 5 Years
1 3
 
 
Operating leases, Total
6 3
 
 
Annual obligation for real estate leases and railroad licenses
1 
 
 
Total rental expense
$ 28 
$ 25 
$ 21 
Commitments And Contingencies (Schedule Of Estimated Purchased Power Commitments) (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2015
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
 
2016
$ 1,323 1
2017
1,145 1
2018
531 1
2019
342 1
2020
215 1
Thereafter
1,128 1
Total
4,684 1
Coal
 
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
 
2016
664 1
2017
685 1
2018
204 1
2019
110 1
2020
0 1
Thereafter
0 1
Total
1,663 1
Natural Gas
 
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
 
2016
249 1 2
2017
190 1 2
2018
127 1 2
2019
89 1 2
2020
43 1 2
Thereafter
60 1 2
Total
758 1 2
Nuclear Fuel
 
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
 
2016
51 1
2017
46 1
2018
68 1
2019
24 1
2020
51 1
Thereafter
108 1
Total
348 1
Purchased Power
 
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
 
2016
241 1 3
2017
147 1 3
2018
72 1 3
2019
58 1 3
2020
58 1 3
Thereafter
539 1 3
Total
1,115 1 3
Methane Gas
 
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
 
2016
3 1
2017
4 1
2018
5 1
2019
5 1
2020
6 1
Thereafter
71 1
Total
94 1
Other
 
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
 
2016
115 1
2017
73 1
2018
55 1
2019
56 1
2020
57 1
Thereafter
350 1
Total
706 1
Union Electric Company
 
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
 
2016
833 
2017
826 
2018
352 
2019
205 
2020
120 
Thereafter
469 
Total
2,805 
Union Electric Company |
Coal
 
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
 
2016
664 
2017
685 
2018
204 
2019
110 
2020
0 
Thereafter
0 
Total
1,663 
Union Electric Company |
Natural Gas
 
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
 
2016
46 2
2017
36 2
2018
24 2
2019
14 2
2020
10 2
Thereafter
23 2
Total
153 2
Union Electric Company |
Nuclear Fuel
 
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
 
2016
51 
2017
46 
2018
68 
2019
24 
2020
51 
Thereafter
108 
Total
348 
Union Electric Company |
Purchased Power
 
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
 
2016
23 
2017
23 
2018
23 
2019
23 
2020
23 
Thereafter
84 
Total
199 
Union Electric Company |
Methane Gas
 
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
 
2016
3 
2017
4 
2018
5 
2019
5 
2020
6 
Thereafter
71 
Total
94 
Union Electric Company |
Other
 
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
 
2016
46 
2017
32 
2018
28 
2019
29 
2020
30 
Thereafter
183 
Total
348 
Ameren Illinois Company
 
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
 
2016
452 
2017
303 
2018
176 
2019
137 
2020
95 
Thereafter
659 
Total
1,822 
Ameren Illinois Company |
Natural Gas
 
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
 
2016
203 2
2017
154 2
2018
103 2
2019
75 2
2020
33 2
Thereafter
37 2
Total
605 2
Ameren Illinois Company |
Purchased Power
 
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
 
2016
218 3
2017
124 3
2018
49 3
2019
35 3
2020
35 3
Thereafter
455 3
Total
916 3
Ameren Illinois Company |
Other
 
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
 
2016
31 
2017
25 
2018
24 
2019
27 
2020
27 
Thereafter
167 
Total
$ 301 
Commitments And Contingencies (Environmental Matters) (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2015
Manufactured Gas Plant
 
Accrual for environmental loss contingencies
$ 232.0 
Manufactured Gas Plant |
Ameren Illinois Company
 
Number of remediation sites
44 
Loss contingency range of possible loss, minimum
232.0 
Loss contingency range of possible loss, maximum
313.0 
Accrual for environmental loss contingencies
232.0 
Former Coal Ash Landfill |
Ameren Illinois Company
 
Loss contingency range of possible loss, minimum
0.5 
Loss contingency range of possible loss, maximum
6.0 
Accrual for environmental loss contingencies
0.5 
Other Environmental |
Ameren Illinois Company
 
Accrual for environmental loss contingencies
0.7 
Former Coal Tar Distillery |
Union Electric Company
 
Loss contingency range of possible loss, minimum
2.0 
Loss contingency range of possible loss, maximum
5.0 
Accrual for environmental loss contingencies
2.0 
Sauget Area 2 |
Union Electric Company
 
Loss contingency range of possible loss, minimum
1.0 
Loss contingency range of possible loss, maximum
2.5 
Accrual for environmental loss contingencies
1.0 
Substation in St Charles, Missouri |
Union Electric Company
 
Accrual for environmental loss contingencies
0.6 
Minimum
 
Estimated capital costs to comply with existing and known federal and state air emissions regulations
600 
Maximum
 
Estimated capital costs to comply with existing and known federal and state air emissions regulations
$ 700 
Commitments And Contingencies (Pumped-Storage Hydroelectric Facility Breach) (Details) (Union Electric Company, USD $)
In Millions, unless otherwise specified
3 Months Ended
Dec. 31, 2015
Mar. 31, 2016
Subsequent Event
Commitments and Contingencies [Line Items]
 
 
Insurance Settlements Receivable
$ 41 
 
Litigation Settlement, Amount
 
$ 42 
Divestiture Transactions and Discontinued Operations (Narrative) (Details) (USD $)
In Millions, unless otherwise specified
1 Months Ended 3 Months Ended
Dec. 31, 2015
New Ameren Energy Resources Company, LLC
Jan. 31, 2014
Elgin, Gibson City and Grand Tower Energy Centers
Dec. 31, 2013
Elgin, Gibson City and Grand Tower Energy Centers
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
 
 
 
Proceeds from Sales of Business, Affiliate and Productive Assets
 
$ 168.0 
$ 137.5 
Loss Contingency Accrual
$ 25 
 
 
Divestiture Transactions and Discontinued Operations (Components of Discontinued Operations in Consolidated Statement of Income) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
 
 
 
Operating revenues
$ 0 
$ 1 
$ 1,037 
Operating benefits (expenses)
1 
(2)
(1,207)1
Operating income (loss)
1 
(1)
(170)
Other income (loss)
0 
0 
(1)
Interest charges
0 
0 
(39)
Income (loss) before income taxes
1 
(1)
(210)
Income tax (expense) benefit
50 
0 
(13)
Income (Loss) from Discontinued Operations, Net of Tax (Note 16)
51 
(1)
(223)
Merchant Generation
 
 
 
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
 
 
 
Impairment of assets to be disposed of
 
 
$ 201 
Divestiture Transactions and Discontinued Operations (Components of Assets and Liabilities on Consolidated Balance Sheet) (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Assets of discontinued operations
 
 
 
Accumulated deferred income taxes, net
$ 14 
$ 15 
 
Total assets of discontinued operations
14 
15 
165 
Liabilities of discontinued operations
 
 
 
Accounts payable and other current obligations
1 
1 
 
Asset retirement obligations
28 1
32 1
 
Total liabilities of discontinued operations
$ 29 
$ 33 
 
Segment Information (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended 12 Months Ended
Dec. 31, 2015
Sep. 30, 2015
Jun. 30, 2015
Mar. 31, 2015
Dec. 31, 2014
Sep. 30, 2014
Jun. 30, 2014
Mar. 31, 2014
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Segment Reporting Information [Line Items]
 
 
 
 
 
 
 
 
 
 
 
Number of reportable segments
 
 
 
 
 
 
 
 
2 
 
 
External revenues
$ 1,308 
$ 1,833 
$ 1,401 
$ 1,556 
$ 1,370 
$ 1,670 
$ 1,419 
$ 1,594 
$ 6,098 
$ 6,053 
$ 5,838 
Depreciation and amortization
 
 
 
 
 
 
 
 
796 
745 
706 
Interest Expense
 
 
 
 
 
 
 
 
355 
341 
398 
Income taxes (benefit)
 
 
 
 
 
 
 
 
363 
377 
311 
Net income (loss) attributable to Ameren common shareholders
29 
343 
150 
108 
48 
293 
149 
96 
630 
586 
289 
Capital expenditures
 
 
 
 
 
 
 
 
1,917 
1,785 
1,379 
TOTAL ASSETS
23,640 
 
 
 
22,289 
 
 
 
23,640 
22,289 
 
Assets of discontinued operations (Note 16)
14 
 
 
 
15 
 
 
 
14 
15 
165 
Net income (loss) attributable to Ameren common shareholders - continuing operations
30 
343 
98 
108 
46 
294 
150 
97 
579 
587 
512 
Union Electric Company
 
 
 
 
 
 
 
 
 
 
 
Segment Reporting Information [Line Items]
 
 
 
 
 
 
 
 
 
 
 
Number of reportable segments
 
 
 
 
 
 
 
 
1 
 
 
External revenues
 
 
 
 
 
 
 
 
3,566 
3,526 
3,516 
Revenue from Related Parties
 
 
 
 
 
 
 
 
43 
27 
25 
Depreciation and amortization
 
 
 
 
 
 
 
 
492 
473 
454 
Interest and dividend income
 
 
 
 
 
 
 
 
28 
28 
27 
Interest Expense
 
 
 
 
 
 
 
 
219 
211 
210 
Income taxes (benefit)
 
 
 
 
 
 
 
 
209 
229 
242 
Net income (loss) attributable to Ameren common shareholders
 
 
 
 
 
 
 
 
352 
390 
395 
Capital expenditures
 
 
 
 
 
 
 
 
622 
747 
648 
TOTAL ASSETS
13,851 1
 
 
 
13,474 1
 
 
 
13,851 1
13,474 1
12,867 1
Ameren Illinois Company
 
 
 
 
 
 
 
 
 
 
 
Segment Reporting Information [Line Items]
 
 
 
 
 
 
 
 
 
 
 
Number of reportable segments
 
 
 
 
 
 
 
 
1 
 
 
External revenues
 
 
 
 
 
 
 
 
2,462 
2,496 
2,307 
Revenue from Related Parties
 
 
 
 
 
 
 
 
4 
2 
4 
Depreciation and amortization
 
 
 
 
 
 
 
 
295 
263 
243 
Interest and dividend income
 
 
 
 
 
 
 
 
12 
7 
2 
Interest Expense
 
 
 
 
 
 
 
 
131 
112 
143 
Income taxes (benefit)
 
 
 
 
 
 
 
 
127 
143 
110 
Net income (loss) attributable to Ameren common shareholders
 
 
 
 
 
 
 
 
214 
201 
160 
Capital expenditures
 
 
 
 
 
 
 
 
918 
835 
701 
TOTAL ASSETS
8,903 1
 
 
 
8,204 1
 
 
 
8,903 1
8,204 1
7,397 1
Other Segment
 
 
 
 
 
 
 
 
 
 
 
Segment Reporting Information [Line Items]
 
 
 
 
 
 
 
 
 
 
 
External revenues
 
 
 
 
 
 
 
 
70 
31 
15 
Revenue from Related Parties
 
 
 
 
 
 
 
 
2 
2 
2 
Depreciation and amortization
 
 
 
 
 
 
 
 
9 
9 
9 
Interest and dividend income
 
 
 
 
 
 
 
 
1 
2 
1 
Interest Expense
 
 
 
 
 
 
 
 
5 
18 
45 
Income taxes (benefit)
 
 
 
 
 
 
 
 
27 
5 
(41)
Net income (loss) attributable to Ameren common shareholders
 
 
 
 
 
 
 
 
13 
(4)
(43)
Capital expenditures
 
 
 
 
 
 
 
 
377 2
203 2
30 2
TOTAL ASSETS
1,139 1
 
 
 
799 1
 
 
 
1,139 1
799 1
711 1
Intersegment Elimination
 
 
 
 
 
 
 
 
 
 
 
Segment Reporting Information [Line Items]
 
 
 
 
 
 
 
 
 
 
 
External revenues
 
 
 
 
 
 
 
 
0 
0 
0 
Revenue from Related Parties
 
 
 
 
 
 
 
 
(49)
(31)
(31)
Depreciation and amortization
 
 
 
 
 
 
 
 
0 
0 
0 
Interest and dividend income
 
 
 
 
 
 
 
 
0 
0 
0 
Interest Expense
 
 
 
 
 
 
 
 
0 
0 
0 
Income taxes (benefit)
 
 
 
 
 
 
 
 
0 
0 
0 
Net income (loss) attributable to Ameren common shareholders
 
 
 
 
 
 
 
 
0 
0 
0 
Capital expenditures
 
 
 
 
 
 
 
 
0 
0 
0 
TOTAL ASSETS
(267)
 
 
 
(203)
 
 
 
(267)
(203)
(233)
Segment, Continuing Operations
 
 
 
 
 
 
 
 
 
 
 
Segment Reporting Information [Line Items]
 
 
 
 
 
 
 
 
 
 
 
External revenues
 
 
 
 
 
 
 
 
6,098 
6,053 
5,838 
Revenue from Related Parties
 
 
 
 
 
 
 
 
0 
0 
0 
Depreciation and amortization
 
 
 
 
 
 
 
 
796 
745 
706 
Interest and dividend income
 
 
 
 
 
 
 
 
41 
37 
30 
Interest Expense
 
 
 
 
 
 
 
 
355 
341 
398 
Income taxes (benefit)
 
 
 
 
 
 
 
 
363 
377 
311 
Capital expenditures
 
 
 
 
 
 
 
 
1,917 
1,785 
1,379 
TOTAL ASSETS
$ 23,626 1 3
 
 
 
$ 22,274 1 3
 
 
 
$ 23,626 1 3
$ 22,274 1 3
$ 20,742 1 3
Selected Quarterly Information (Summary Of Selected Quarterly Information) (Details) (USD $)
In Millions, except Per Share data, unless otherwise specified
3 Months Ended 12 Months Ended
Dec. 31, 2015
Sep. 30, 2015
Jun. 30, 2015
Mar. 31, 2015
Dec. 31, 2014
Sep. 30, 2014
Jun. 30, 2014
Mar. 31, 2014
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Selected Quarterly Financial Information [Line Items]
 
 
 
 
 
 
 
 
 
 
 
Operating revenues
$ 1,308 
$ 1,833 
$ 1,401 
$ 1,556 
$ 1,370 
$ 1,670 
$ 1,419 
$ 1,594 
$ 6,098 
$ 6,053 
$ 5,838 
Operating Income
140 
626 
237 
256 
125 
561 
322 
246 
1,259 
1,254 
1,184 
Net income
30 
345 
151 
110 
49 
295 
150 
98 
636 
592 
295 
Net income attributable to Ameren common shareholders - continuing operations
30 
343 
98 
108 
46 
294 
150 
97 
579 
587 
512 
Net Income (Loss) Attributable to Ameren common shareholders- Discontinued Operations
(1)
0 
52 
0 
2 
(1)
(1)
(1)
51 
(1)
(223)
Net income attributable to Ameren common shareholders
29 
343 
150 
108 
48 
293 
149 
96 
630 
586 
289 
Earnings per common share - basic - continuing operations
$ 0.12 
$ 1.42 
$ 0.40 
$ 0.45 
$ 0.19 
$ 1.21 
$ 0.62 
$ 0.40 
$ 2.39 
$ 2.42 
$ 2.11 
Earnings (loss) per common share - basic - discontinued operations
$ 0.00 
$ 0.00 
$ 0.21 
$ 0.00 
$ 0.01 
$ 0.00 
$ (0.01)
$ 0.00 
$ 0.21 
$ 0.00 
$ (0.92)
Earnings per common share - basic
$ 0.12 
$ 1.42 
$ 0.61 
$ 0.45 
$ 0.20 
$ 1.21 
$ 0.61 
$ 0.40 
$ 2.60 
$ 2.42 
$ 1.19 
Earnings per common share - diluted - continuing operations
$ 0.12 
$ 1.41 
$ 0.40 
$ 0.45 
$ 0.19 
$ 1.20 
$ 0.62 
$ 0.40 
$ 2.38 
$ 2.40 
$ 2.10 
Earnings (loss) per common share - diluted - discontinued operations
$ 0.00 
$ 0.00 
$ 0.21 
$ 0.00 
$ 0.01 
$ 0.00 
$ (0.01)
$ 0.00 
$ 0.21 
$ 0.00 
$ (0.92)
Earnings per common share - diluted
$ 0.12 
$ 1.41 
$ 0.61 
$ 0.45 
$ 0.20 
$ 1.20 
$ 0.61 
$ 0.40 
$ 2.59 
$ 2.40 
$ 1.18 
Union Electric Company
 
 
 
 
 
 
 
 
 
 
 
Selected Quarterly Financial Information [Line Items]
 
 
 
 
 
 
 
 
 
 
 
Operating revenues
754 
1,171 
884 
800 
739 
1,097 
900 
817 
3,609 
3,553 
3,541 
Operating Income
58 
423 
146 
115 
29 
394 
243 
119 
742 
785 
803 
Net income
 
 
 
 
 
 
 
 
355 
393 
398 
Net income attributable to Ameren common shareholders
11 
240 
62 
42 
(5)
223 
127 
48 
355 
393 
398 
Net Income (Loss) Available to Common Shareholder
11 
239 
61 
41 
(5)
222 
126 
47 
352 
390 
395 
Ameren Illinois Company
 
 
 
 
 
 
 
 
 
 
 
Selected Quarterly Financial Information [Line Items]
 
 
 
 
 
 
 
 
 
 
 
Operating revenues
553 
655 
513 
745 
633 
572 
519 
774 
2,466 
2,498 
2,311 
Operating Income
74 
189 
83 
120 
97 
158 
75 
120 
466 
450 
415 
Net income
 
 
 
 
 
 
 
 
217 
204 
163 
Net income attributable to Ameren common shareholders
33 
98 
32 
54 
46 
75 
29 
54 
217 
204 
163 
Net Income (Loss) Available to Common Shareholder
$ 32 
$ 98 
$ 31 
$ 53 
$ 45 
$ 75 
$ 28 
$ 53 
$ 214 
$ 201 
$ 160 
Schedule I - Condensed Financial Information Of Parent (Statement of Income) (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended 12 Months Ended
Dec. 31, 2015
Sep. 30, 2015
Jun. 30, 2015
Mar. 31, 2015
Dec. 31, 2014
Sep. 30, 2014
Jun. 30, 2014
Mar. 31, 2014
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items]
 
 
 
 
 
 
 
 
 
 
 
Operating revenues
$ 1,308 
$ 1,833 
$ 1,401 
$ 1,556 
$ 1,370 
$ 1,670 
$ 1,419 
$ 1,594 
$ 6,098 
$ 6,053 
$ 5,838 
Operating expenses
 
 
 
 
 
 
 
 
4,839 
4,799 
4,654 
Operating loss
140 
626 
237 
256 
125 
561 
322 
246 
1,259 
1,254 
1,184 
Interest income from affiliates
 
 
 
 
 
 
 
 
14 1 2
10 1 2
3 1 2
Other Nonoperating Income (Expense)
 
 
 
 
 
 
 
 
44 
57 
43 
Interest charges
 
 
 
 
 
 
 
 
355 
341 
398 
Income taxes (benefit)
 
 
 
 
 
 
 
 
363 
377 
311 
Net income attributable to Ameren common shareholders - continuing operations
30 
343 
98 
108 
46 
294 
150 
97 
579 
587 
512 
Net Income (Loss) Attributable to Ameren common shareholders- Discontinued Operations
(1)
0 
52 
0 
2 
(1)
(1)
(1)
51 
(1)
(223)
Net income attributable to Ameren common shareholders
29 
343 
150 
108 
48 
293 
149 
96 
630 
586 
289 
Comprehensive Income from Continuing Operations
 
 
 
 
 
 
 
 
 
 
 
Pension and other postretirement activity, net of income taxes (benefit)
 
 
 
 
 
 
 
 
6 
(12)
30 
Comprehensive Income from Continuing Operations Attributable to Ameren Common Shareholders
 
 
 
 
 
 
 
 
585 
575 
542 
Other Comprehensive Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest
 
 
 
 
 
 
 
 
 
0 
(18)
Comprehensive Income (Loss) from Discontinued Operations Attributable to Ameren Common shareholders
 
 
 
 
 
 
 
 
51 
(1)
(242)
Comprehensive Income (Loss) Attributable to Ameren Common Shareholders
 
 
 
 
 
 
 
 
636 
574 
300 
Other Comprehensive Income (Loss), Taxes:
 
 
 
 
 
 
 
 
 
 
 
Pension and other postretirement activity, tax (benefit)
 
 
 
 
 
 
 
 
3 
(7)
16 
Parent Company
 
 
 
 
 
 
 
 
 
 
 
Condensed Financial Statements, Captions [Line Items]
 
 
 
 
 
 
 
 
 
 
 
Operating expenses
 
 
 
 
 
 
 
 
14 
11 
26 
Operating loss
 
 
 
 
 
 
 
 
(14)
(11)
(26)
Equity in earnings of subsidiaries
 
 
 
 
 
 
 
 
600 
607 
546 
Interest income from affiliates
 
 
 
 
 
 
 
 
6 
3 
3 
Other Nonoperating Income (Expense)
 
 
 
 
 
 
 
 
(5)
2 
(5)
Interest charges
 
 
 
 
 
 
 
 
3 
16 
42 
Income taxes (benefit)
 
 
 
 
 
 
 
 
5 
(2)
(36)
Net income attributable to Ameren common shareholders - continuing operations
 
 
 
 
 
 
 
 
579 
587 
512 
Net Income (Loss) Attributable to Ameren common shareholders- Discontinued Operations
 
 
 
 
 
 
 
 
51 
(1)
(223)
Net income attributable to Ameren common shareholders
 
 
 
 
 
 
 
 
630 
586 
289 
Comprehensive Income from Continuing Operations
 
 
 
 
 
 
 
 
 
 
 
Pension and other postretirement activity, net of income taxes (benefit)
 
 
 
 
 
 
 
 
6 
(12)
30 
Comprehensive Income from Continuing Operations Attributable to Ameren Common Shareholders
 
 
 
 
 
 
 
 
585 
575 
542 
Other Comprehensive Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest
 
 
 
 
 
 
 
 
0 
0 
(19)
Comprehensive Income (Loss) from Discontinued Operations Attributable to Ameren Common shareholders
 
 
 
 
 
 
 
 
51 
(1)
(242)
Comprehensive Income (Loss) Attributable to Ameren Common Shareholders
 
 
 
 
 
 
 
 
636 
574 
300 
Other Comprehensive Income (Loss), Taxes:
 
 
 
 
 
 
 
 
 
 
 
Pension and other postretirement activity, tax (benefit)
 
 
 
 
 
 
 
 
$ 3 
$ (7)
$ 16 
Schedule I - Condensed Financial Information Of Parent (Balance Sheet) (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
ASSETS
 
 
 
 
Cash and cash equivalents
$ 292 
$ 5 
$ 30 
$ 209 
Miscellaneous accounts and notes receivable
98 
81 
 
 
Other current assets
88 
86 
 
 
Total current assets
1,917 
1,694 
 
 
Deferred Tax Assets, Net of Valuation Allowance, Noncurrent
6 
13 
 
 
Other non-current assets
575 
629 
 
 
TOTAL ASSETS
23,640 
22,289 
 
 
LIABILITIES AND EQUITY
 
 
 
 
Short-term debt
301 
714 
 
 
Other current liabilities
379 
434 
 
 
Total current liabilities
2,093 
2,249 
 
 
Long-term Debt, Net
6,880 
6,085 
 
 
Pension and other postretirement benefits
580 
705 
 
 
Other deferred credits and liabilities
531 
514 
 
 
Commitments and Contingencies
   
   
 
 
Retained earnings
1,331 
1,103 
 
 
Accumulated other comprehensive loss
(3)
(9)
 
 
Total equity
7,088 
6,855 
6,686 
 
TOTAL LIABILITIES AND EQUITY
23,640 
22,289 
 
 
Parent Company
 
 
 
 
ASSETS
 
 
 
 
Cash and cash equivalents
0 
1 
11 
23 
Advances to money pool
0 
55 
 
 
Accounts receivable - affiliates
53 
28 
 
 
Notes Receivable, Related Parties, Current
0 
94 
 
 
Miscellaneous accounts and notes receivable
3 
39 
 
 
Other current assets
9 
14 
 
 
Total current assets
65 
231 
 
 
Investments in subsidiaries - continuing operations
7,231 
6,680 
 
 
Investments in subsidiaries - discontinued operations
(4)
(4)
 
 
Note receivable - affiliates
290 
100 
 
 
Deferred Tax Assets, Net of Valuation Allowance, Noncurrent
426 
407 
 
 
Other non-current assets
158 
152 
 
 
TOTAL ASSETS
8,166 
7,566 
 
 
LIABILITIES AND EQUITY
 
 
 
 
Short-term debt
301 
585 
 
 
Borrowings from money pool
14 
0 
 
 
Accounts payable – affiliates
75 
88 
 
 
Other current liabilities
22 
52 
 
 
Total current liabilities
412 
725 
 
 
Long-term Debt, Net
694 
0 
 
 
Pension and other postretirement benefits
33 
47 
 
 
Other deferred credits and liabilities
81 
81 
 
 
Total liabilities
1,220 
853 
 
 
Common stock, $.01 par value, 400.0 shares authorized – shares outstanding of 242.6
2 
2 
 
 
Other paid-in capital, principally premium on common stock
5,616 
5,617 
 
 
Retained earnings
1,331 
1,103 
 
 
Accumulated other comprehensive loss
(3)
(9)
 
 
Total equity
6,946 
6,713 
 
 
TOTAL LIABILITIES AND EQUITY
$ 8,166 
$ 7,566 
 
 
Schedule I - Condensed Financial Information Of Parent (Statement of Cash Flows) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items]
 
 
 
Net cash provided by operating activities
$ 2,017 
$ 1,551 
$ 1,693 
Cash Flows From Investing Activities:
 
 
 
Proceeds from Collection of Notes Receivable
20 
95 
6 
Contributions to Note Receivable
(8)
(89)
(5)
Other
20 
11 
1 
Net Cash Provided by (Used in) Investing Activities
(1,976)
(1,717)
(1,723)
Cash flows from financing activities:
 
 
 
Dividends on common stock
(402)
(390)
(388)
Short-term debt, net
(413)
346 
368 
Repayments of Other Long-term Debt
(120)
(697)
(399)
Issuances of Long-term debt
1,197 
898 
278 
Capital issuance costs
(12)
(11)
(2)
Other
2 
1 
0 
Net cash provided by (used in) financing activities
246 
141 
(149)
Net change in cash and cash equivalents
287 
(25)
(179)
Cash and cash equivalents at beginning of year
5 
30 
209 
Cash and cash equivalents at end of year
292 
5 
30 
Parent Company
 
 
 
Condensed Financial Statements, Captions [Line Items]
 
 
 
Net cash provided by operating activities
537 
514 
453 
Cash Flows From Investing Activities:
 
 
 
Money pool advances, net
55 
279 
(371)
Intercompany notes receivable, net
(96)
(134)
(23)
Investments in subsidiaries
(509)
(280)
(50)
Return of investments
0 
215 
1 
Proceeds from Collection of Notes Receivable
20 
95 
6 
Contributions to Note Receivable
(8)
(89)
(5)
Other
(24)
(12)
(3)
Net Cash Provided by (Used in) Investing Activities
(562)
74 
(445)
Cash flows from financing activities:
 
 
 
Dividends on common stock
(402)
(390)
(388)
Short-term debt, net
(284)
217 
368 
Money pool borrowings, net
14 
0 
0 
Repayments of Other Long-term Debt
0 
(425)
0 
Issuances of Long-term debt
700 
0 
0 
Capital issuance costs
(6)
0 
0 
Other
2 
0 
0 
Net cash provided by (used in) financing activities
24 
(598)
(20)
Net change in cash and cash equivalents
(1)
(10)
(12)
Cash and cash equivalents at beginning of year
1 
11 
23 
Cash and cash equivalents at end of year
0 
1 
11 
Cash dividends received from consolidated subsidiaries
575 
340 
570 
Noncash investing activity - divestiture
0 
0 
494 
Noncash Investing activity- investment in subsidiaries
$ (38)
$ (19)
$ 0 
Schedule I - Condensed Financial Information Of Parent (Impairment and Other Charges) (Details) (USD $)
12 Months Ended 1 Months Ended 3 Months Ended 3 Months Ended 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2015
Parent Company
Dec. 31, 2014
Parent Company
Dec. 31, 2013
Parent Company
Dec. 31, 2013
Parent Company
Merchant Generation
Dec. 31, 2015
New Ameren Energy Resources Company, LLC
Dec. 31, 2015
New Ameren Energy Resources Company, LLC
Parent Company
May 31, 2014
Senior Unsecured Notes8875 Due2014 [Member]
Parent Company
Dec. 31, 2015
Senior Unsecured Notes270 due 2020 [Member]
Parent Company
Dec. 31, 2015
Senior Unsecured Notes365 due 2026 [Member]
Parent Company
Dec. 31, 2015
Unsecured Debt [Member]
Senior Unsecured Notes270 due 2020 [Member]
Parent Company
Dec. 31, 2014
Unsecured Debt [Member]
Senior Unsecured Notes270 due 2020 [Member]
Parent Company
Dec. 31, 2015
Unsecured Debt [Member]
Senior Unsecured Notes365 due 2026 [Member]
Parent Company
Dec. 31, 2014
Unsecured Debt [Member]
Senior Unsecured Notes365 due 2026 [Member]
Parent Company
Dec. 31, 2015
2013 Tax Year [Member]
Parent Company
Impairment and Other Charges [Line Items]
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Deferred Income Taxes and Other Assets, Current
 
$ 352,000,000 
 
 
$ 143,000,000 
 
 
 
 
 
 
 
 
 
 
 
 
Guarantees Outstanding
 
 
 
36,000,000 
 
 
 
 
 
 
 
 
 
 
 
 
 
Debt instrument face amount
 
 
 
 
 
 
 
 
 
 
 
 
350,000,000 
0 
350,000,000 
0 
 
Proceeds from issuance of secured debt
 
 
 
 
 
 
 
 
 
 
 
 
348,000,000 
 
347,000,000 
 
 
Repayments of Other Long-term Debt
120,000,000 
697,000,000 
399,000,000 
0 
425,000,000 
0 
 
 
 
425,000,000 
 
 
 
 
 
 
 
Long-term debt interest rate
 
 
 
 
 
 
 
 
 
8.875% 
2.70% 
3.65% 
2.70% 
 
3.65% 
 
 
Impairment charge on long-lived assets and related charges
 
 
 
 
 
 
201,000,000 
 
 
 
 
 
 
 
 
 
 
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
53,000,000 
Loss Contingency Accrual
 
 
 
 
 
 
 
$ 25,000,000 
$ 25,000,000 
 
 
 
 
 
 
 
 
Schedule II - Valuation And Qualifying Accounts (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Allowance For Doubtful Accounts
 
 
 
Valuation and Qualifying Accounts Disclosure [Line Items]
 
 
 
Balance at Beginning of Period
$ 21 
$ 18 
$ 17 
Charged to Costs and Expenses
33 
36 
35 
Charged to Other Accounts
5 1
4 1
4 1
Deductions
40 2
37 2
38 2
Balance at End of Period
19 
21 
18 
Valuation Allowance of Deferred Tax Assets
 
 
 
Valuation and Qualifying Accounts Disclosure [Line Items]
 
 
 
Balance at Beginning of Period
10 
7 
2 
Charged to Costs and Expenses
4 
3 
5 
Charged to Other Accounts
(8)1
0 1
0 1
Deductions
0 
0 
0 
Balance at End of Period
6 
10 
7 
Union Electric Company |
Allowance For Doubtful Accounts
 
 
 
Valuation and Qualifying Accounts Disclosure [Line Items]
 
 
 
Balance at Beginning of Period
8 
5 
5 
Charged to Costs and Expenses
13 
16 
16 
Charged to Other Accounts
0 1
0 1
0 1
Deductions
14 2
13 2
16 2
Balance at End of Period
7 
8 
5 
Union Electric Company |
Valuation Allowance of Deferred Tax Assets
 
 
 
Valuation and Qualifying Accounts Disclosure [Line Items]
 
 
 
Balance at Beginning of Period
1 
1 
1 
Charged to Costs and Expenses
0 
0 
0 
Charged to Other Accounts
(1)1
0 1
0 1
Deductions
0 
0 
0 
Balance at End of Period
0 
1 
1 
Ameren Illinois Company |
Allowance For Doubtful Accounts
 
 
 
Valuation and Qualifying Accounts Disclosure [Line Items]
 
 
 
Balance at Beginning of Period
13 
13 
12 
Charged to Costs and Expenses
20 
20 
19 
Charged to Other Accounts
5 1
4 1
4 1
Deductions
26 2
24 2
22 2
Balance at End of Period
12 
13 
13 
Ameren Illinois Company |
Valuation Allowance of Deferred Tax Assets
 
 
 
Valuation and Qualifying Accounts Disclosure [Line Items]
 
 
 
Balance at Beginning of Period
1 
1 
1 
Charged to Costs and Expenses
0 
0 
0 
Charged to Other Accounts
(1)1
0 1
0 1
Deductions
0 
0 
0 
Balance at End of Period
$ 0 
$ 1 
$ 1