AMEREN CORP, 10-Q filed on 11/4/2016
Quarterly Report
Document and Entity Information
9 Months Ended
Sep. 30, 2016
Oct. 31, 2016
Entity Information [Line Items]
 
 
Document Type
10-Q 
 
Amendment Flag
false 
 
Document Period End Date
Sep. 30, 2016 
 
Document Fiscal Year Focus
2016 
 
Document Fiscal Period Focus
Q3 
 
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 
Union Electric Company
 
 
Entity Information [Line Items]
 
 
Document Type
10-Q 
 
Amendment Flag
false 
 
Document Period End Date
Sep. 30, 2016 
 
Document Fiscal Year Focus
2016 
 
Document Fiscal Period Focus
Q3 
 
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 
Ameren Illinois Company
 
 
Entity Information [Line Items]
 
 
Document Type
10-Q 
 
Amendment Flag
false 
 
Document Period End Date
Sep. 30, 2016 
 
Document Fiscal Year Focus
2016 
 
Document Fiscal Period Focus
Q3 
 
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 
Consolidated Statement of Income (Loss) (USD $)
In Millions, except Per Share data, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Operating Revenues:
 
 
 
 
Electric
$ 1,725 
$ 1,700 
$ 4,101 
$ 4,093 
Gas
134 
133 
619 
697 
Total operating revenues
1,859 
1,833 
4,720 
4,790 
Operating Expenses:
 
 
 
 
Fuel
205 
259 
574 
670 
Purchased power
178 
153 
451 
393 
Gas purchased for resale
34 
38 
227 
320 
Other operations and maintenance
411 
428 
1,246 
1,256 
Provision for Callaway construction and operating license
0 
0 
0 
69 
Depreciation and amortization
211 
201 
628 
594 
Taxes other than income taxes
129 
128 
358 
369 
Total operating expenses
1,168 
1,207 
3,484 
3,671 
Operating Income
691 
626 
1,236 
1,119 
Other Income and Expenses:
 
 
 
 
Miscellaneous income
18 1
19 1
54 1
54 1
Miscellaneous expense
8 1
5 1
21 1
22 1
Total other income (expense)
10 
14 
33 
32 
Interest Charges
97 
87 
287 
264 
Income Before Income Taxes
604 
553 
982 
887 
Income Taxes
233 
208 
356 
333 
Income from Continuing Operations
371 
345 
626 
554 
Income from Discontinued Operations, Net of Taxes
0 
0 
0 
52 
Net Income (Loss)
371 
345 
626 
606 
Pension and other postretirement benefit plan activity, net of income taxes (benefit)
(1)
0 
1 
4 
Comprehensive Income
368 
343 
622 
605 
Less: Net Income (Loss) Attributable to Noncontrolling Interests:
 
 
 
 
Net Income from Continuing Operations Attributable to Noncontrolling Interests
2 
2 
5 
5 
Net Income (Loss):
 
 
 
 
Continuing Operations
369 
343 
621 
549 
Discontinued Operations
0 
0 
0 
52 
Net Income (Loss)
369 
343 
621 
601 
Earnings Per Share, Basic [Abstract]
 
 
 
 
Continuing Operations
$ 1.52 
$ 1.42 
$ 2.56 
$ 2.27 
Discontinued Operations
$ 0 
$ 0 
$ 0 
$ 0.21 
Earnings Per Share, Basic
$ 1.52 
$ 1.42 
$ 2.56 
$ 2.48 
Earnings Per Share, Diluted [Abstract]
 
 
 
 
Income (Loss) from Continuing Operations, Per Diluted Share
$ 1.52 
$ 1.41 
$ 2.56 
$ 2.26 
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share
$ 0 
$ 0 
$ 0 
$ 0.21 
Earnings Per Share, Diluted
$ 1.52 
$ 1.41 
$ 2.56 
$ 2.47 
Dividends per Common Share
$ 0.425 
$ 0.41 
$ 1.275 
$ 1.23 
Average Common Shares Outstanding - Basic
242.6 
242.6 
242.6 
242.6 
Weighted Average Number of Shares Outstanding, Diluted
242.9 
243.9 
243.0 
243.8 
Union Electric Company
 
 
 
 
Operating Revenues:
 
 
 
 
Electric
1,144 
1,151 
2,682 
2,752 
Gas
20 
19 
90 
101 
Other Revenue, Net
1 
1 
1 
2 
Total operating revenues
1,165 
1,171 
2,773 
2,855 
Operating Expenses:
 
 
 
 
Fuel
205 
259 
574 
670 
Purchased power
77 
29 
169 
87 
Gas purchased for resale
6 
5 
33 
43 
Other operations and maintenance
220 
233 
670 
673 
Provision for Callaway construction and operating license
0 
0 
0 
69 
Depreciation and amortization
130 
125 
384 
367 
Taxes other than income taxes
96 
97 
252 
262 
Total operating expenses
734 
748 
2,082 
2,171 
Operating Income
431 
423 
691 
684 
Other Income and Expenses:
 
 
 
 
Miscellaneous income
14 
14 
38 
37 
Miscellaneous expense
2 
3 
6 
8 
Total other income (expense)
12 
11 
32 
29 
Interest Charges
53 
54 
158 
164 
Income Before Income Taxes
390 
380 
565 
549 
Income Taxes
148 
140 
215 
205 
Net Income (Loss)
242 
240 
350 
344 
Other Comprehensive Income
0 
0 
0 
0 
Comprehensive Income
242 
240 
350 
344 
Net Income (Loss):
 
 
 
 
Net Income (Loss)
242 
240 
350 
344 
Earnings Per Share, Diluted [Abstract]
 
 
 
 
Preferred Stock Dividends
1 
1 
3 
3 
Net Income Available to Common Stockholder
241 
239 
347 
341 
Ameren Illinois Company
 
 
 
 
Operating Revenues:
 
 
 
 
Electric
562 
540 
1,365 
1,316 
Gas
114 
115 
530 
597 
Total operating revenues
676 
655 
1,895 
1,913 
Operating Expenses:
 
 
 
 
Purchased power
110 
128 
304 
317 
Gas purchased for resale
28 
33 
194 
277 
Other operations and maintenance
198 
202 
592 
606 
Depreciation and amortization
80 
74 
237 
220 
Taxes other than income taxes
30 
29 
98 
101 
Total operating expenses
446 
466 
1,425 
1,521 
Operating Income
230 
189 
470 
392 
Other Income and Expenses:
 
 
 
 
Miscellaneous income
4 
4 
15 
15 
Miscellaneous expense
3 
3 
11 
10 
Total other income (expense)
1 
1 
4 
5 
Interest Charges
35 
33 
105 
99 
Income Before Income Taxes
196 
157 
369 
298 
Income Taxes
77 
59 
144 
114 
Net Income (Loss)
119 
98 
225 
184 
Pension and other postretirement benefit plan activity, net of income taxes (benefit)
(1)
0 
(3)
(2)
Comprehensive Income
118 
98 
222 
182 
Net Income (Loss):
 
 
 
 
Net Income (Loss)
119 
98 
225 
184 
Earnings Per Share, Diluted [Abstract]
 
 
 
 
Preferred Stock Dividends
0 
0 
2 
2 
Net Income Available to Common Stockholder
$ 119 
$ 98 
$ 223 
$ 182 
Consolidated Statement of Income (Loss) (Parenthetical) (USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Pension and other postretirement benefit plan activity, tax expense (benefit)
$ 0 
$ 0 
$ 4 
$ 4 
Ameren Illinois Company
 
 
 
 
Pension and other postretirement benefit plan activity, tax expense (benefit)
$ (1)
$ (1)
$ (2)
$ (2)
Consolidated Statement of Comprehensive Income (Loss) (USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
 
 
 
 
Income from Continuing Operations
$ 371 
$ 345 
$ 626 
$ 554 
Other Comprehensive Income from Continuing Operations, Net of Taxes
 
 
 
 
Pension and other postretirement benefit plan activity, net of income taxes (benefit)
(1)
0 
1 
4 
Comprehensive Income from Continuing Operations
370 
345 
627 
558 
Less: Comprehensive Income from Continuing Operations Attributable to Noncontrolling Interests
2 
2 
5 
5 
Comprehensive Income from Continuing Operations Attributable to Ameren Common Shareholders
368 
343 
622 
553 
Comprehensive Income from Discontinued Operations Attributable to Ameren Common Shareholders
0 
0 
0 
52 
Comprehensive Income Attributable to Ameren Common Shareholders
$ 368 
$ 343 
$ 622 
$ 605 
Consolidated Statement of Comprehensive Income (Loss) Consolidated Statement of Income (Parenthetical) (USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
 
 
 
 
Pension and other postretirement benefit plan activity, tax expense (benefit)
$ 0 
$ 0 
$ 4 
$ 4 
Consolidated Balance Sheet (USD $)
In Millions, unless otherwise specified
Sep. 30, 2016
Dec. 31, 2015
Current Assets:
 
 
Cash and cash equivalents
$ 18 
$ 292 
Accounts receivable - trade (less allowance for doubtful accounts)
543 
388 
Unbilled revenue
240 
239 
Miscellaneous accounts and notes receivable
49 
98 
Materials and supplies
551 
538 
Current regulatory assets
107 
260 
Other current assets
76 
88 
Assets of discontinued operations
15 
14 
Total current assets
1,599 
1,917 
Property and Plant, Net
19,647 
18,799 
Investments and Other Assets:
 
 
Nuclear decommissioning trust fund
599 
556 
Goodwill
411 
411 
Regulatory assets
1,312 
1,382 
Other assets
566 
575 
Total investments and other assets
2,888 
2,924 
TOTAL ASSETS
24,134 
23,640 
Current Liabilities:
 
 
Current maturities of long-term debt
431 
395 
Short-term Debt
608 
301 
Accounts and wages payable
513 
777 
Taxes accrued
159 
43 
Interest accrued
110 
89 
Customer deposits
104 
100 
Current regulatory liabilities
87 
80 
Other current liabilities
252 
279 
Liabilities of discontinued operations
27 
29 
Total current liabilities
2,291 
2,093 
Long-term Debt, Net
6,607 
6,880 
Deferred Credits and Other Liabilities:
 
 
Accumulated deferred income taxes, net
4,255 
3,885 
Accumulated deferred investment tax credits
56 
60 
Regulatory liabilities
1,974 
1,905 
Asset retirement obligations
636 
618 
Pension and other postretirement benefits
499 
580 
Other deferred credits and liabilities
481 
531 
Total deferred credits and other liabilities
7,901 
7,579 
Commitments and Contingencies
   
   
Stockholders' Equity:
 
 
Common Stock
2 
2 
Other paid-in capital
5,550 
5,616 
Retained earnings
1,643 
1,331 
Accumulated other comprehensive income (loss)
(2)
(3)
Stockholder's equity
7,193 
6,946 
Noncontrolling Interest
142 
142 
Total equity
7,335 
7,088 
TOTAL LIABILITIES AND EQUITY
24,134 
23,640 
Union Electric Company
 
 
Current Assets:
 
 
Cash and cash equivalents
1 
199 
Advances to money pool
201 
36 
Accounts receivable - trade (less allowance for doubtful accounts)
272 
174 
Accounts receivable - affiliates
20 
54 
Unbilled revenue
144 
128 
Miscellaneous accounts and notes receivable
33 
78 
Materials and supplies
392 
387 
Current regulatory assets
47 
89 
Other current assets
37 
41 
Total current assets
1,147 
1,186 
Property and Plant, Net
11,294 
11,183 
Investments and Other Assets:
 
 
Nuclear decommissioning trust fund
599 
556 
Regulatory assets
514 
605 
Other assets
335 
321 
Total investments and other assets
1,448 
1,482 
TOTAL ASSETS
13,889 
13,851 
Current Liabilities:
 
 
Current maturities of long-term debt
431 
266 
Short-term Debt
0 
0 
Accounts and wages payable
209 
417 
Accounts payable - affiliates
89 
56 
Taxes accrued
149 
31 
Interest accrued
66 
59 
Current regulatory liabilities
11 
28 
Other current liabilities
116 
120 
Total current liabilities
1,071 
977 
Long-term Debt, Net
3,569 
3,844 
Deferred Credits and Other Liabilities:
 
 
Accumulated deferred income taxes, net
3,003 
2,844 
Accumulated deferred investment tax credits
54 
58 
Regulatory liabilities
1,211 
1,172 
Asset retirement obligations
630 
612 
Pension and other postretirement benefits
183 
234 
Other deferred credits and liabilities
21 
28 
Total deferred credits and other liabilities
5,102 
4,948 
Commitments and Contingencies
   
   
Stockholders' Equity:
 
 
Common Stock
511 
511 
Other paid-in capital
1,824 
1,822 
Preferred stock
80 
80 
Retained earnings
1,732 
1,669 
Stockholder's equity
4,147 
4,082 
TOTAL LIABILITIES AND EQUITY
13,889 
13,851 
Ameren Illinois Company
 
 
Current Assets:
 
 
Cash and cash equivalents
3 
71 
Accounts receivable - trade (less allowance for doubtful accounts)
259 
204 
Accounts receivable - affiliates
13 
22 
Unbilled revenue
96 
111 
Miscellaneous accounts and notes receivable
11 
19 
Materials and supplies
159 
151 
Current regulatory assets
59 
167 
Other current assets
17 
15 
Total current assets
617 
760 
Property and Plant, Net
7,285 
6,848 
Investments and Other Assets:
 
 
Goodwill
411 
411 
Regulatory assets
791 
771 
Other assets
98 
113 
Total investments and other assets
1,300 
1,295 
TOTAL ASSETS
9,202 
8,903 
Current Liabilities:
 
 
Current maturities of long-term debt
0 
129 
Short-term Debt
157 
0 
Due to Related Parties, Current
54 
0 
Accounts and wages payable
214 
249 
Accounts payable - affiliates
59 
66 
Taxes accrued
8 
13 
Interest accrued
40 
28 
Customer deposits
68 
69 
Mark-to-market derivative liabilities
21 
45 
Current environmental remediation
35 
28 
Current regulatory liabilities
56 
39 
Other current liabilities
99 
86 
Total current liabilities
811 
752 
Long-term Debt, Net
2,344 
2,342 
Deferred Credits and Other Liabilities:
 
 
Accumulated deferred income taxes, net
1,618 
1,480 
Accumulated deferred investment tax credits
2 
2 
Regulatory liabilities
761 
732 
Pension and other postretirement benefits
262 
271 
Environmental remediation
171 
205 
Other deferred credits and liabilities
212 
222 
Total deferred credits and other liabilities
3,026 
2,912 
Commitments and Contingencies
   
   
Stockholders' Equity:
 
 
Common Stock
0 
0 
Other paid-in capital
2,005 
2,005 
Preferred stock
62 
62 
Retained earnings
952 
825 
Accumulated other comprehensive income (loss)
2 
5 
Stockholder's equity
3,021 
2,897 
TOTAL LIABILITIES AND EQUITY
$ 9,202 
$ 8,903 
Consolidated Balance Sheet (Parenthetical) (USD $)
In Millions, except Per Share data, unless otherwise specified
Sep. 30, 2016
Dec. 31, 2015
Accounts receivable - trade allowance for doubtful accounts
$ 19 
$ 19 
Common stock, par value
$ 0.01 
$ 0.01 
Common stock, shares authorized
400.0 
400.0 
Common stock, shares outstanding
242.6 
242.6 
Union Electric Company
 
 
Accounts receivable - trade allowance for doubtful accounts
7 
7 
Common stock, par value
$ 5 
$ 5 
Common stock, shares authorized
150.0 
150.0 
Common stock, shares outstanding
102.1 
102.1 
Ameren Illinois Company
 
 
Accounts receivable - trade allowance for doubtful accounts
$ 12 
$ 12 
Common stock, no par value
$ 0 
$ 0 
Common stock, shares authorized
45.0 
45.0 
Common stock, shares outstanding
25.5 
25.5 
Consolidated Statement of Cash Flows (USD $)
In Millions, unless otherwise specified
9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Cash Flows From Operating Activities:
 
 
Net income
$ 626 
$ 606 
Income from discontinued operations, net of taxes
0 
(52)
Adjustments to reconcile net income to net cash provided by operating activities:
 
 
Provision for Callaway construction and operating license
0 
69 
Depreciation and amortization
625 
582 
Amortization of nuclear fuel
63 
71 
Amortization of debt issuance costs and premium/discounts
17 
16 
Deferred income taxes and investment tax credits, net
364 
318 
Allowance for equity funds used during construction
(20)1
(19)1
Share-based compensation costs
17 
20 
Other
(9)
(8)
Changes in assets and liabilities:
 
 
Receivables
(134)
(71)
Materials and supplies
(13)
(23)
Accounts and wages payable
(196)
(172)
Taxes accrued
119 
116 
Regulatory assets and liabilities
146 
74 
Assets, other
9 
17 
Liabilities, other
(29)
(26)
Pension and other postretirement benefits
(26)
29 
Net cash provided by operating activities – continuing operations
1,559 
1,547 
Net cash used in operating activities – discontinued operations
0 
(5)
Net cash provided by operating activities
1,559 
1,542 
Cash Flows From Investing Activities:
 
 
Capital expenditures
(1,496)
(1,332)
Nuclear fuel expenditures
(41)
(30)
Purchases of securities - nuclear decommissioning trust fund
(310)
(301)
Sales and maturities of securities - nuclear decommissioning trust fund
297 
290 
Proceeds from Notes Receivable
0 
12 
Contributions to Note Receivable
0 
(8)
Other
(1)
7 
Net cash used in investing activities – continuing operations
(1,551)
(1,362)
Net cash used in investing activities – discontinued operations
0 
0 
Net cash used in investing activities
(1,551)
(1,362)
Cash Flows From Financing Activities:
 
 
Dividends on common stock
(309)
(298)
Dividends paid to noncontrolling interest holders
(5)
(5)
Short-term debt, net
307 
69 
Maturities of Long-term Debt
(389)
(114)
Issuances of Long-term Debt
149 
249 
Employee payroll taxes related to share-based payments
(32)
(12)
Capital Issuance Costs
(1)
(2)
Other
(2)
0 
Net cash provided by (used in) financing activities – continuing operations
(282)
(113)
Net change in cash and cash equivalents
(274)
67 
Cash and cash equivalents at beginning of period
292 
5 
Cash and cash equivalents at end of period
18 
72 
Union Electric Company
 
 
Cash Flows From Operating Activities:
 
 
Net income
350 
344 
Adjustments to reconcile net income to net cash provided by operating activities:
 
 
Provision for Callaway construction and operating license
0 
69 
Depreciation and amortization
381 
356 
Amortization of nuclear fuel
63 
71 
Amortization of debt issuance costs and premium/discounts
5 
5 
Deferred income taxes and investment tax credits, net
159 
88 
Allowance for equity funds used during construction
(16)
(16)
Other
0 
1 
Changes in assets and liabilities:
 
 
Receivables
(95)
(51)
Materials and supplies
(5)
(26)
Accounts and wages payable
(176)
(177)
Taxes accrued
165 
243 
Regulatory assets and liabilities
60 
101 
Assets, other
(8)
6 
Liabilities, other
13 
11 
Pension and other postretirement benefits
(8)
15 
Net cash provided by operating activities
888 
1,040 
Cash Flows From Investing Activities:
 
 
Capital expenditures
(500)
(444)
Nuclear fuel expenditures
(41)
(30)
Purchases of securities - nuclear decommissioning trust fund
(310)
(301)
Sales and maturities of securities - nuclear decommissioning trust fund
297 
290 
Money pool advances, net
(165)
(250)
Other
(5)
(4)
Net cash used in investing activities
(724)
(739)
Cash Flows From Financing Activities:
 
 
Dividends on common stock
(285)
(490)
Dividends on preferred stock
(3)
(3)
Short-term debt, net
0 
(97)
Maturities of Long-term Debt
(260)
(114)
Issuances of Long-term Debt
149 
249 
Capital contribution from parent
38 
224 
Capital Issuance Costs
(1)
(2)
Net cash provided by (used in) financing activities
(362)
(233)
Net change in cash and cash equivalents
(198)
68 
Cash and cash equivalents at beginning of period
199 
1 
Cash and cash equivalents at end of period
1 
69 
Ameren Illinois Company
 
 
Cash Flows From Operating Activities:
 
 
Net income
225 
184 
Adjustments to reconcile net income to net cash provided by operating activities:
 
 
Depreciation and amortization
236 
218 
Amortization of debt issuance costs and premium/discounts
11 
11 
Deferred income taxes and investment tax credits, net
141 
108 
Allowance for equity funds used during construction
(4)
(3)
Other
(8)
(7)
Changes in assets and liabilities:
 
 
Receivables
(36)
45 
Materials and supplies
(8)
3 
Accounts and wages payable
(17)
11 
Taxes accrued
5 
(10)
Regulatory assets and liabilities
75 
(31)
Assets, other
11 
6 
Liabilities, other
6 
(10)
Pension and other postretirement benefits
(14)
13 
Net cash provided by operating activities
627 
541 
Cash Flows From Investing Activities:
 
 
Capital expenditures
(683)
(620)
Other
4 
5 
Net cash used in investing activities
(679)
(615)
Cash Flows From Financing Activities:
 
 
Dividends on common stock
(95)
0 
Dividends on preferred stock
(2)
(2)
Short-term debt, net
157 
(32)
Money pool borrowings, net
54 
107 
Maturities of Long-term Debt
(129)
0 
Other
(1)
0 
Net cash provided by (used in) financing activities
(16)
73 
Net change in cash and cash equivalents
(68)
(1)
Cash and cash equivalents at beginning of period
71 
1 
Cash and cash equivalents at end of period
$ 3 
$ 0 
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. Also see the Glossary of Terms and Abbreviations at the front of this report and in the Form 10-K.
•
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 Illinois Company, doing business as Ameren Illinois, operates rate-regulated electric and natural gas transmission and distribution businesses in Illinois.
Additionally, Ameren 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 evaluating competitive electric transmission investment opportunities outside of these territories, including investments outside of MISO. Ameren also has various other subsidiaries that conduct activities such as the provision of shared services.
Unless otherwise stated, these notes to Ameren’s financial statements exclude discontinued operations for all periods presented. See Note 12 – Discontinued Operations in this report and Note 16 – Divestiture Transactions and Discontinued Operations under Part II, Item 8, of the Form 10-K for additional information.
Ameren’s financial statements are prepared on a consolidated basis and therefore include the accounts of its majority-owned subsidiaries. All intercompany transactions have been eliminated. Ameren Missouri and Ameren Illinois have no subsidiaries, and therefore their financial statements are not prepared on a consolidated basis. 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 statement 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. The results of operations of an interim period may not give a true indication of results that may be expected for a full year. These financial statements should be read in conjunction with the financial statements and the notes thereto included in the Form 10-K.
Asset Retirement Obligations
AROs at Ameren, Ameren Missouri, and Ameren Illinois increased during the nine months ended September 30, 2016, to reflect the accretion of the estimated obligation due to the passage of time, partially offset by immaterial settlements.
Share-based Compensation
A summary of nonvested performance share units at September 30, 2016, and changes during the nine months ended September 30, 2016, 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, 2016
1,024,870

 
$
46.08

Granted(a)
587,197

 
44.13

Forfeitures
(15,949
)
 
45.07

Vested(b)
(23,114
)
 
44.41

Nonvested at September 30, 2016
1,573,004

 
$
45.39

(a)
Performance share units granted to certain executive and nonexecutive officers and other eligible employees under the 2014 Incentive Plan.
(b)
Performance share units vested due to the 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.
The fair value of each performance share unit awarded in 2016 under the 2014 Incentive Plan was determined to be $44.13, which was based on Ameren’s closing common share price of $43.23 at December 31, 2015, 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, 2016. The simulations can produce a greater fair value for the performance share unit than the December 31 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 1.31%, volatility of 15% to 20% for the peer group, and Ameren’s attainment of a three-year average earnings per share threshold during the performance period.
Excise Taxes
Ameren Missouri and Ameren Illinois collect certain excise taxes from customers 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 and 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 the customer and are therefore not included in Ameren Illinois’ revenues and expenses. The following table presents excise taxes recorded in “Operating Revenues – Electric,” “Operating Revenues – Gas” and “Operating Expenses – Taxes other than income taxes” for the three and nine months ended September 30, 2016 and 2015:
 
Three Months
 
Nine Months
 
2016
 
2015
 
2016
 
2015
Ameren Missouri
$
52

 
$
52

 
$
122

 
$
127

Ameren Illinois
9

 
9

 
40

 
42

Ameren
$
61

 
$
61

 
$
162

 
$
169


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 0.3 million and 0.4 million in the three and nine months ended September 30, 2016, respectively, and 1.3 million and 1.2 million, respectively, in the year-ago periods. There were no potentially dilutive securities excluded from the earnings per diluted share calculations for the three and nine months ended September 30, 2016 and 2015. The calculation of diluted earnings per share prospectively reflected the adoption of FASB guidance related to employee share-based payment accounting discussed below.
Accounting and Reporting Developments
Below is a summary of recently issued authoritative accounting standards relevant to 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 impact 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. The guidance will be effective for the Ameren Companies in the first quarter of 2018.
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, similar legal entities, and certain investment funds, (2) the evaluation of fees paid to a decision maker or service provider as a variable interest, (3) how fee arrangements impact the primary beneficiary determination, and (4) the evaluation of related party relationships on the primary beneficiary determination. The adoption of this guidance in the first quarter of 2016 did not impact the Ameren Companies’ results of operations, financial position, liquidity, or disclosures.
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, with an option for entities to adopt early. Upon adoption, the Ameren Companies will recognize and measure operating leases on their respective balance sheets at the beginning of the earliest period presented. The Ameren Companies are currently assessing the impact of this guidance on their results of operations, financial position, statement of cash flows, and disclosures.
Improvements to Employee Share-Based Payment Accounting
In March 2016, the FASB issued authoritative accounting guidance that simplifies the accounting for share-based payment transactions, including the income tax consequences, the calculation of diluted earnings per share, the treatment of forfeitures, the classification of awards as either equity or liabilities, and the classification on the statement of cash flows. Ameren determines for each performance share unit award whether the difference between the deduction for tax purposes and the compensation cost recognized for financial reporting purposes results in either an excess tax benefit or an excess tax deficit. Previously, excess tax benefits were recognized in "Other paid-in capital" on Ameren’s consolidated balance sheet, and in certain cases, excess tax deficits were recognized in “Income taxes” on Ameren’s consolidated income statement. The new guidance increases income statement volatility by requiring all excess tax benefits and deficits to be recognized in “Income taxes,” and treated as discrete items in the period in which they occur. Ameren adopted this guidance in the first quarter of 2016 and prospectively applied the amendment in this guidance requiring recognition of excess tax benefits and deficits in the income statement, which resulted in recognition of a $21 million income tax benefit and a corresponding $21 million increase in income from continuing operations and net income (9 cents per diluted share) during that period. Also as a result of the adoption of this guidance, Ameren made an accounting policy election to continue to estimate the number of forfeitures expected to occur. The amendments in the guidance that require application using a modified retrospective transition method did not impact Ameren. Therefore, there was no cumulative-effect adjustment to retained earnings recognized as of January 1, 2016. Ameren applied the amendments in this guidance relating to classification on the statement of cash flows retrospectively. As a result, for the nine months ended September 30, 2015, Ameren reclassified, for comparison purposes, $2 million of excess tax benefits on the statement of cash flows from financing to operating activity, and $12 million of employee payroll taxes related to share-based payments from operating to financing activity.
Rate And Regulatory Matters
RATE AND REGULATORY MATTERS
RATE AND REGULATORY MATTERS
Below is a summary of updates to significant regulatory proceedings and related lawsuits. See also Note 2 – Rate and Regulatory Matters under Part II, Item 8, of the Form 10-K. 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 impact on our results of operations, financial position, or liquidity.
Missouri
2016 Electric Rate Case
On July 1, 2016, Ameren Missouri filed a request with the MoPSC seeking approval to increase its annual revenues for electric service by $206 million. The electric rate increase request is based on a 9.9% return on equity, a capital structure comprised of 51.8% equity, a rate base of $7.2 billion, and a test year ended March 31, 2016, with certain pro-forma adjustments through the true-up date of December 31, 2016. The rate request includes $74 million that primarily relates to nearly $1.4 billion of new gross electric infrastructure investments since the true-up date in Ameren Missouri’s last electric rate case. This $74 million includes depreciation expenses of $39 million, return on rate base of $25 million, and increased property taxes of $10 million. The rate request also includes $51 million related to reduced customer sales volumes, including reductions from the suspended operations at the New Madrid Smelter, and $34 million related to increases in transmission charges. Other changes in expenses reflected in the rate request include decreases in pension and other post-employment benefit plan expenses of $24 million and solar rebate expenses of $15 million, both of which are subject to regulatory tracking mechanisms; increased net energy costs, excluding the impact of the suspended operations at the New Madrid Smelter and other customer sales volumes, of $23 million; and increased income taxes of $15 million.
As a part of its filing, Ameren Missouri requested the amortization over ten years of an estimated $81 million of lost fixed cost recovery due to lower sales volumes, as discussed below, from the New Madrid Smelter during the period April 2015 through May 2017.
Ameren Missouri also requested continued use of its FAC and the regulatory tracking mechanisms for pension and postretirement benefits and uncertain income tax positions that the MoPSC previously authorized in earlier electric rate orders. Additionally, Ameren Missouri requested the implementation of a new regulatory tracking mechanism for transmission charges and revenues.
The MoPSC proceeding relating to the proposed electric service rate changes will take place over a period of up to 11 months, with a decision by the MoPSC expected by late April 2017 and new rates effective in late May 2017. Ameren Missouri cannot predict the level of any electric service rate change the MoPSC may approve, when any rate change may go into effect, whether the requested regulatory tracking mechanisms will be approved, or whether any rate increase that may eventually be approved will be sufficient for Ameren Missouri to recover its costs and earn a reasonable return on its investments when the increase goes into effect.
Noranda and New Madrid Smelter
In the first quarter of 2016, Noranda suspended operations at the New Madrid Smelter and filed voluntary petitions for a court-supervised restructuring process under Chapter 11 of the United States Bankruptcy Code. In October 2016, Noranda sold the New Madrid Smelter to ARG International AG. As of September 30, 2016, Ameren Missouri has been paid in full for all previous electric service amounts, and expects to continue to be paid in full for the minimal amount of electric service it is currently providing to the New Madrid Smelter.
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 the New Madrid Smelter’s portion of Ameren Missouri’s revenue requirement. In 2016, as a result of the suspended operations, actual sales volumes to the New Madrid Smelter are significantly below the sales volumes reflected in rates. As a result, full recovery by Ameren Missouri of its revenue requirement has not occurred and will not occur until rates are adjusted prospectively by the MoPSC in the July 2016 electric rate case to accurately reflect the actual sales volumes to the New Madrid Smelter. In its July 2016 electric rate case, Ameren Missouri is seeking to recover the April 2015 through May 2017 lost fixed costs caused by the lower sales volumes to New Madrid Smelter. Also, as a result of the New Madrid Smelter’s suspended operations, Ameren Missouri is applying 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 sales to the smelter. The current market price of electricity is less than the New Madrid Smelter’s electric rate, and Ameren Missouri expects market prices to remain below the New Madrid Smelter’s electric rate through the date that new rates in the July 2016 rate case become effective. Accordingly, this FAC-tariff provision will not enable Ameren Missouri to fully recover its revenue requirement under current market conditions. Operations at the New Madrid Smelter remain suspended and Ameren Missouri is uncertain of future sales to the smelter.
MEEIA 2013
The MEEIA 2013 performance incentive allowed 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 September 2016, Ameren Missouri and the MoPSC staff filed a stipulation agreement with the MoPSC that supported a $29 million MEEIA 2013 performance incentive. The MoOPC opposed this stipulation agreement; however, it did not oppose the conclusion that Ameren Missouri achieved at least 100% of the customer energy efficiency goals. As there was no challenge to the achievement of at least 100% of the customer energy efficiency goals, Ameren Missouri recognized $19 million of revenue during the third quarter of 2016 related to the MEEIA 2013 performance incentive. In November 2016, the MoPSC approved a $28 million MEEIA 2013 performance incentive based on a revised stipulation agreement between Ameren Missouri, the MoPSC staff, and the MoOPC. As a result, Ameren Missouri will recognize $9 million of additional revenues in the fourth quarter of 2016 relating to the MEEIA 2013 performance incentive. Further, the revised stipulation agreement included a provision to incorporate the results of the appeal, discussed below, regarding the determination of an input used to calculate the performance incentive.
In November 2015, the MoPSC issued an order regarding the determination of an input used to calculate the performance incentive. Ameren Missouri filed an appeal of the order with the Missouri Court of Appeals, Western District, which is expected to issue a decision in 2016. If the Missouri Court of Appeals, Western District, overturns the November 2015 MoPSC order, Ameren Missouri may recognize additional revenues in excess of the $28 million approved by the MoPSC in November 2016.
ATXI’s Mark Twain Project
The Mark Twain project is a MISO-approved 95-mile transmission line to be located in northeast Missouri. In April 2016, the MoPSC granted ATXI a certificate of convenience and necessity for the Mark Twain project. Before starting construction, ATXI must obtain assents for road crossings from the five counties where the line will be constructed. None of the five county commissions approved ATXI’s requests for the assents. In October 2016, ATXI filed suit in each of the five county circuit courts to obtain the assents. A decision from each of the county circuit courts is expected in 2017. ATXI plans to complete the project in 2018; however, delays in obtaining the assents could delay the completion date.
Illinois
IEIMA
Under the provisions of the IEIMA's performance-based formula rate-making framework, which currently extends through 2019, Ameren Illinois’ electric distribution 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 September 30, 2016, Ameren Illinois had recorded regulatory assets of $23 million, $66 million, and $22 million to reflect its expected 2016 and 2015 revenue requirement reconciliation adjustments, and the approved 2014 revenue requirement reconciliation adjustment, with interest, respectively.
In April 2016, Ameren Illinois filed with the ICC its annual electric distribution service formula rate update to establish the revenue requirement used for 2017 rates. Pending ICC approval, Ameren Illinois’ update filing will result in a $14 million decrease in Ameren Illinois’ electric distribution service revenue requirement, beginning in January 2017. This update reflects an increase to the annual formula rate based on 2015 actual costs and expected net plant additions for 2016, an increase to include the 2015 revenue requirement reconciliation adjustment, and a decrease for the conclusion of the 2014 revenue requirement reconciliation adjustment, which will be fully collected from customers in 2016, consistent with the ICC’s December 2015 annual update filing order. As of December 31, 2015, Ameren Illinois had recorded a regulatory asset of $103 million related to the approved 2014 revenue requirement reconciliation adjustment. In October 2016, an administrative law judge issued a proposed order that reflected a decrease to Ameren Illinois’ electric distribution service revenue requirement of $14 million. An ICC decision on the revenue requirement used for 2017 rates is expected by December 2016.
Federal
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 September 2016, the FERC issued a final order in the November 2013 complaint case which lowered the allowed base return on common equity to 10.32%. The order was consistent with the initial decision an administrative law judge issued in December 2015 and requires customer refunds, with interest, to be issued for the 15-month period ended February 2015. In addition, the new allowed base return on common equity is reflected in rates prospectively from the September 2016 effective date of the order. Refunds for the November 2013 complaint case are expected to be issued in the first half of 2017.
After 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%. In June 2016, an administrative law judge issued an initial decision in the February 2015 complaint case which would lower the allowed base return on common equity to 9.70% and would require customer refunds, with interest, to be issued for the 15-month period ended May 2016. The FERC is expected to issue a final order in the February 2015 complaint case in the second quarter of 2017. The final order in the February 2015 complaint case will determine the allowed base return on common equity for the 15-month period ended May 2016. The final order in the February 2015 complaint case will also establish the allowed base return on common equity that will apply prospectively from its expected second quarter 2017 effective date, replacing the 10.32% allowed base return on common equity, which became effective in September 2016. The 12.38% allowed base return on common equity was effective for the period that began at the conclusion of the 15-month period for the February 2015 complaint case in May 2016 through the September 2016 effective date of the final order in the November 2013 complaint case.
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 reduces any refund to customers relating to a reduction of the allowed base return on common equity from the complaint cases discussed above and will also be applied prospectively from the effective date of the September 2016 FERC order, resulting in a current allowed return on common equity of 10.82%.
As of September 30, 2016, Ameren and Ameren Illinois recorded current regulatory liabilities of $61 million and $42 million, respectively, to reflect the expected refunds, including interest, associated with the reduced allowed base returns on common equity in the September 2016 FERC order and the initial decision in the February 2015 complaint case. Ameren Missouri did not record a liability as of September 30, 2016, as 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.
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.
The Missouri Credit Agreement and the Illinois Credit Agreement, both of which expire on December 11, 2019, were not utilized for direct borrowings during the nine months ended September 30, 2016, but were used to support commercial paper issuances and to issue letters of credit. Based on commercial paper outstanding, as well as letters of credit issued under the Credit Agreements, the aggregate amount of credit capacity available under the Credit Agreements to Ameren (parent), Ameren Missouri, and Ameren Illinois, collectively, at September 30, 2016, was $1.5 billion.
Commercial Paper
The following table presents commercial paper outstanding as of September 30, 2016, and December 31, 2015:
  
2016
 
2015
Ameren (parent)
$
451

 
$
301

Ameren Missouri
—

 
—

Ameren Illinois
157

 
—

Ameren Consolidated
$
608

 
$
301

The following table summarizes the borrowing activity and relevant interest rates under Ameren’s (parent), Ameren Missouri’s, and Ameren Illinois’ commercial paper programs for the nine months ended September 30, 2016 and 2015:
 
 
Ameren
(parent)
Ameren
Missouri
Ameren
Illinois
Ameren Consolidated
2016
 
 
 
 
 
 
Average daily commercial paper outstanding
 
$
435

 
$
80

$
48

$
563

Weighted-average interest rate
 
0.81
%
 
0.74
%
0.72
%
0.79
%
Peak commercial paper during period(a)
 
$
574

 
$
208

$
195

$
839

Peak interest rate
 
0.95
%
 
0.85
%
0.85
%
0.95
%
2015
 
 
 
 
 
 
Average daily commercial paper outstanding
 
$
770

 
$
56

$
6

$
832

Weighted-average interest rate
 
0.56
%
 
0.50
%
0.44
%
0.56
%
Peak commercial paper during period(a)
 
$
874

 
$
294

$
48

$
1,108

Peak interest rate
 
0.70
%
 
0.60
%
0.60
%
0.70
%

(a)
The timing of peak commercial paper issuances varies by company; 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 financial covenants in the Credit Agreements. See Note 4 – Short-term Debt and Liquidity under Part II, Item 8, in the Form 10-K for a detailed description of these provisions. 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 Ameren, Ameren Missouri, and Ameren Illinois to each 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 September 30, 2016, the ratios of consolidated indebtedness to consolidated total capitalization, calculated in accordance with the provisions of the Credit Agreements, were 51%, 48%, and 46% for Ameren, Ameren Missouri, and Ameren Illinois, respectively. In addition, under the Credit Agreements, if Ameren does not have a senior long-term unsecured credit rating of at least Baa3 from Moody’s or BBB- from S&P, Ameren is required to maintain a ratio of consolidated funds from operations plus interest expense to consolidated interest expense of at least 2.0 to 1.0. As of September 30, 2016, Ameren’s senior long-term unsecured credit rating exceeded the minimum rating requirements; therefore, the interest coverage requirement was not applicable. Failure of 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 will also be 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 arrangements contain credit rating triggers that would cause a default or acceleration of repayment of outstanding balances. The Ameren Companies were in compliance with the covenants in their credit agreements at September 30, 2016.
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 (parent) and Ameren Services may participate in the utility money pool only as lenders. Surplus internal funds are contributed to the utility 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 money pool participants from the utility money pool at any given time is reduced by the amount of borrowings made by participants, but is increased to the extent that the money 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 utility money pool 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 utility money pool for the three and nine months ended September 30, 2016, was 0.53% and 0.54%, respectively (2015 – 0.10% and 0.09%, respectively).
See Note 8 – Related Party Transactions for the amount of interest income and expense from the money pool arrangements recorded by the Ameren Companies for the nine months ended September 30, 2016 and 2015.
Long-Term Debt And Equity Financings
LONG-TERM DEBT AND EQUITY FINANCINGS
LONG-TERM DEBT AND EQUITY FINANCINGS
Ameren Missouri
In February 2016, Ameren Missouri's $260 million of 5.40% senior secured notes matured and were repaid with cash on hand and commercial paper borrowings.
In June 2016, Ameren Missouri issued $150 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, 2016. Ameren Missouri received proceeds of $148 million, which were used to repay commercial paper borrowings.
Ameren Illinois
In June 2016, Ameren Illinois’ $54 million of 6.20% senior secured notes and $75 million of 6.25% senior secured notes matured and were repaid with commercial paper borrowings.
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 first mortgage bonds or preferred stock. The following table summarizes the required and actual interest coverage ratios for interest charges, dividend coverage ratios, and first mortgage bonds and preferred stock issuable as of September 30, 2016, at an assumed annual 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
 
4.7
$
3,838
 
≥2.5
 
105.9
$
2,357
 
Ameren Illinois
 
≥2.0
 
7.3
 
3,942
(d) 
≥1.5
 
3.0
 
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 first mortgage bonds issuable based either on required coverage ratios or unfunded property additions, whichever is more restrictive. The amounts shown also include first mortgage bonds issuable based on retired bond capacity of $1,206 million and $279 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 first mortgage bonds issuable by Ameren Illinois based on unfunded property additions and retired bonds solely under the former IP mortgage indenture. The amount of first mortgage 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 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 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 committed to the FERC to maintain a minimum of 30% equity in its capital structure. As of September 30, 2016, Ameren Illinois had 51% equity in its capital structure.
In order for the Ameren Companies to issue securities in the future, we have to comply with all applicable requirements in effect at the time of any such issuances.
Off-Balance-Sheet Arrangements
At September 30, 2016, 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 for the three and nine months ended September 30, 2016 and 2015:
 
Three Months
 
Nine Months
 
 
2016
 
2015
 
2016
 
2015
 
Ameren:(a)
 
 
 
 
 
 
 
 
Miscellaneous income:
 
 
 
 
 
 
 
 
Allowance for equity funds used during construction
$
7

 
$
8

 
$
20

 
$
19

 
Interest income on industrial development revenue bonds
7

 
7

 
20

 
20

 
Interest income
3

 
4

 
11

 
12

 
Other
1

 
—

 
3

 
3

 
Total miscellaneous income
$
18

 
$
19

 
$
54

 
$
54

 
Miscellaneous expense:
 
 
 
 
 
 
 
 
Donations
$
1

 
$
—

 
$
8

 
$
10

 
Other
7

 
5

 
13

 
12

 
Total miscellaneous expense
$
8

 
$
5

 
$
21

 
$
22

 
Ameren Missouri:
 
 
 
 
 
 
 
 
Miscellaneous income:
 
 
 
 
 
 
 
 
Allowance for equity funds used during construction
$
6

 
$
7

 
$
16

 
$
16

 
Interest income on industrial development revenue bonds
7

 
7

 
20

 
20

 
Interest income
1

 
—

 
1

 
1

 
Other
—

 
—

 
1

  
—

 
Total miscellaneous income
$
14

 
$
14

 
$
38

 
$
37

 
Miscellaneous expense:
 
 
 
 
 
 
 
 
Donations
$
—

 
$
—

 
$
2

 
$
3

 
Other
2

 
3

 
4

 
5

 
Total miscellaneous expense
$
2

 
$
3

 
$
6

 
$
8

 
 
Three Months
 
Nine Months
 
 
2016
 
2015
 
2016
 
2015
 
Ameren Illinois:
 
 
 
 
 
 
 
 
Miscellaneous income:
 
 
 
 
 
 
 
 
Allowance for equity funds used during construction
$
1

 
$
1

 
$
4

 
$
3

 
Interest income
2

 
3

 
9

 
10

 
Other
1

 
—

 
2

 
2

 
Total miscellaneous income
$
4

 
$
4

 
$
15

 
$
15

 
Miscellaneous expense:
 
 
 
 
 
 
 
 
Donations
$
1

 
$
—

 
$
6

 
$
4

 
Other
2

 
3

 
5

 
6

 
Total miscellaneous expense
$
3

 
$
3

 
$
11

 
$
10

 
(a)
Includes amounts for Ameren registrant and nonregistrant subsidiaries and intercompany eliminations.
Derivative Financial Instruments
DERIVATIVE FINANCIAL INSTRUMENTS
NOTE 6 – 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 September 30, 2016, and December 31, 2015. As of September 30, 2016, these contracts extended through October 2018, March 2021, May 2032, and February 2020 for fuel oils, natural gas, power, and uranium, respectively.
  
Quantity (in millions, except as indicated)
 
2016
2015
Commodity
Ameren Missouri
Ameren Illinois
Ameren
Ameren Missouri
Ameren Illinois
Ameren
Fuel oils (in gallons)(a)
25

(b)

25

35

(b)

35

Natural gas (in mmbtu)
26

128

154

30

151

181

Power (in megawatthours)
1

9

10

1

10

11

Uranium (pounds in thousands)
445

(b)

445

494

(b)

494

(a)
Consists of ultra-low-sulfur diesel products.
(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 7 – Fair Value Measurements for a 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 the resulting gains or losses 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 liabilities in the period in which the change occurs. We believe derivative losses and gains deferred as regulatory assets and liabilities are probable of recovery, or refund, through future rates charged to customers. Regulatory assets and 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 September 30, 2016, and December 31, 2015, all contracts that met the definition of a derivative and are not eligible for the NPNS exception received 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 September 30, 2016, and December 31, 2015:
 
Balance Sheet Location
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
2016
 
 
 
 
 
 
Fuel oils
Other assets
 
$
1

 
$
—

 
$
1

Natural gas
Other current assets
 
—

 
2

 
2

 
Other assets
 
—

 
1

 
1

Power
Other current assets
 
11

 
—

 
11

 
Total assets (a)
 
$
12

 
$
3

 
$
15

Fuel oils
Other current liabilities
 
$
8

 
$
—

 
$
8

 
Other deferred credits and liabilities
 
1

 
—

 
1

Natural gas
MTM derivative liabilities
 
(b)

 
9

 
(b)

 
Other current liabilities
 
3

 
—

 
12

 
Other deferred credits and liabilities
 
6

 
9

 
15

Power
MTM derivative liabilities
 
(b)

 
12

 
(b)

 
Other current liabilities
 
2

 
—

 
14

 
Other deferred credits and liabilities
 
—

 
160

 
160

Uranium
Other current liabilities
 
2

 
—

 
2

 
Other deferred credits and liabilities
 
3

 
—

 
3

 
Total liabilities (c)
 
$
25

 
$
190

 
$
215

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


(a)
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)
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. 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 September 30, 2016, and December 31, 2015:
 
 
 
 
Gross Amounts Not Offset in the Balance Sheet
 
 
Commodity Contracts Eligible to be Offset
 
Gross Amounts Recognized in the Balance Sheet
 
Derivative Instruments
 
Cash Collateral Received/Posted(a)
 
Net
Amount
2016
 
 
 
 
 
 
 
 
Assets:
 
 
 
 
 
 
 
 
Ameren Missouri
 
$
12

 
$
2

 
$
—

 
$
10

Ameren Illinois
 
3

 
2

 
—

 
1

Ameren
 
$
15

 
$
4

 
$
—

 
$
11

Liabilities:
 
 
 
 
 
 
 
 
Ameren Missouri
 
$
25

 
$
2

 
$
5

 
$
18

Ameren Illinois
 
190

 
2

 
—

 
188

Ameren
 
$
215

 
$
4

 
$
5

 
$
206

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

(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 calculated 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 September 30, 2016, if counterparty groups were to fail completely to perform on contracts, the Ameren Companies’ 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 our credit ratings were downgraded, or if a counterparty with reasonable grounds for uncertainty regarding our ability to satisfy an obligation requested adequate assurance of performance, additional collateral postings might be required. The following table presents, as of September 30, 2016, 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 September 30, 2016, 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)
2016
 
 
 
 
 
Ameren Missouri
$
69

 
$
2

 
$
60

Ameren Illinois
53

 
—

 
46

Ameren
$
122

 
$
2

 
$
106

(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 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 three hierarchy levels. See Note 8 – Fair Value Measurements under Part II, Item 8, of the Form 10-K for information related to hierarchy levels. 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 September 30, 2016, and December 31, 2015:
 
 
Fair Value
 
 
 
Weighted Average
 
 
Assets
Liabilities
Valuation Technique(s)
Unobservable Input
Range
Level 3 Derivative asset and liability – commodity contracts(a):
 
 
 
2016
 
 
 
 
 
 
 
 
Fuel oils
$
1

$
—

Option model
Volatilities(%)(b)
25 – 38
26
 
 
 
 
Discounted cash flow
Counterparty credit risk(%)(c)(d)
0.22
(e)
 
 
 
 
 
Ameren Missouri credit risk(%)(c)(d)
0.38
(d)
 
Power(f)
11

(174
)
Discounted cash flow
Average forward peak and off-peak pricing – forwards/swaps ($/MWh)(g)
25 – 42
29
 
 
 
 
 
Estimated auction price for FTRs ($/MW)(b)
(253) – 3,593
31
 
 
 
 
 
Nodal basis ($/MWh)(g)
(6) – 0
(2)
 
 
 
 
 
Ameren credit risk (%)(c)(d)
0.38
(e)
 
 
 
 
Fundamental energy production model
Estimated future gas prices ($/mmbtu)(b)
3 – 5
4
 
 
 
 
 
Escalation rate (%)(b)(h)
4
(e)
 
 
 
 
Contract price allocation
Estimated renewable energy credit costs ($/credit)(b)
5 – 7
6
 
Uranium
—

(5
)
Option model
Volatilities (%)(b)
20
(e)
 
 
 
 
Discounted cash flow
Average forward uranium pricing ($/pound)(b)
22 – 26
24
 
 
 
 
 
Ameren Missouri credit risk (%)(c)(d)
0.38
(e)
 
 
Fair Value
 
 
 
Weighted Average
 
 
Assets
Liabilities
Valuation Technique(s)
Unobservable Input
Range
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)
 
 
 
 
 
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)

(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 2020. Valuations beyond 2020 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 due to their opposing positions.
(h)
Escalation rate applies to power prices in 2031 and beyond for September 30, 2016, and to power prices in 2026 and beyond for December 31, 2015.
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 the first nine months of 2016 or 2015. At September 30, 2016, and December 31, 2015, 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 September 30, 2016:
 
 
 
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
 
$
—

 
$
—

 
$
1

 
$
1

 
 
Natural gas
 
$
—

 
$
3

 
$
—

 
$
3

 
 
Power
 
—

 
—

 
11

 
11

 
 
Total derivative assets – commodity contracts
 
$
—

 
$
3

 
$
12

 
$
15

 
 
Nuclear decommissioning trust fund:
 
 
 
 
 
 
 
 
 
 
Cash and cash equivalents
 
$
3

 
$
—

 
$
—

 
$
3

 
 
Equity securities:
 
 
 
 
 
 
 
 
 
 
U.S. large capitalization
 
393

 
—

 
—

 
393

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

 
120

 
—

 
120

 
 
Corporate bonds
 
—

 
64

 
—

 
64

 
 
Other
 
—

 
17

 
—

 
17

 
 
Total nuclear decommissioning trust fund
 
$
396

 
$
201

 
$
—

 
$
597

(b) 
 
Total Ameren
 
$
396

 
$
204

 
$
12

 
$
612

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

 
$
—

 
$
1

 
$
1

 
 
Power
 
—

 
—

 
11

 
11

 
 
Total derivative assets – commodity contracts
 
$
—

 
$
—

 
$
12

 
$
12

 
 
Nuclear decommissioning trust fund:
 
 
 
 
 
 
 
 
 
 
Cash and cash equivalents
 
$
3

 
$
—

 
$
—

 
$
3

 
 
Equity securities:
 
 
 
 
 
 
 
 
 
 
U.S. large capitalization
 
393

 
—

 
—

 
393

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

 
120

 
—

 
120

 
 
Corporate bonds
 
—

 
64

 
—

 
64

 
 
Other
 
—

 
17

 
—

 
17

 
 
Total nuclear decommissioning trust fund
 
$
396

 
$
201

 
$
—

 
$
597

(b) 
 
Total Ameren Missouri
 
$
396

 
$
201

 
$
12

 
$
609

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

 
$
3

 
$
—

 
$
3

 
Liabilities:
 
 
 
 
 
 
 
 
 
 
Ameren
Derivative liabilities – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
9

 
$
—

 
$
—

 
$
9

 
 
Natural gas
 
—

 
27

 
—

 
27

 
 
Power
 
—

 
—

 
174

 
174

 
 
Uranium
 
—

 
—

 
5

 
5

 
 
Total Ameren
 
$
9

 
$
27

 
$
179

 
$
215

 
Ameren
Derivative liabilities – commodity contracts(a):
 
 
 
 
 
 
 
 
 
Missouri
Fuel oils
 
$
9

 
$
—

 
$
—

 
$
9

 
 
Natural gas
 
—

 
9

 
—

 
9

 
 
Power
 
—

 
—

 
2

 
2

 
 
Uranium
 
—

 
—

 
5

 
5

 
 
Total Ameren Missouri
 
$
9

 
$
9

 
$
7

 
$
25

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

 
$
18

 
$
—

 
$
18

 
 
Power
 
—

 
—

 
172

 
172

 
 
Total Ameren Illinois
 
$
—

 
$
18

 
$
172

 
$
190

 
(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 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
Derivative assets – commodity contracts(a):
 
 
 
 
 
 
 
 
 
Missouri
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
Derivative assets – commodity contracts(a):
 
 
 
 
 
 
 
 
 
Illinois
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

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

 
$
—

 
$
—

 
$
29

 
 
Natural gas
 
—

 
13

 
1

 
14

 
 
Uranium
 
—

 
—

 
1

 
1

 
 
Total Ameren Missouri
 
$
29

 
$
13

 
$
2

 
$
44

 
Ameren
Derivative liabilities – commodity contracts(a):
 
 
 
 
 
 
 
 
 
Illinois
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.
All costs related to financial assets and liabilities classified as Level 3 in the fair value hierarchy are expected to be recoverable through customer rates; therefore, there is no impact to net income resulting from changes in the fair value of these instruments. For the three and nine months ended September 30, 2016 and 2015, the balances and changes in the fair value of Level 3 financial assets and liabilities associated with fuel oils, natural gas, and uranium were immaterial.
The following table summarizes the changes in the fair value of power financial assets and liabilities classified as Level 3 in the fair value hierarchy:
  
 
Net derivative commodity contracts
 
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
For the three months ended September 30, 2016
 
 
 
 
 
 
Beginning balance at July 1, 2016
$
14

$
(169
)
$
(155
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities
 
—

 
(6
)
 
(6
)
Settlements
 
(5
)
 
3

 
(2
)
Ending balance at September 30, 2016
$
9

$
(172
)
$
(163
)
Change in unrealized gains (losses) related to assets/liabilities held at September 30, 2016
$
—

$
(2
)
$
(2
)
For the three months ended September 30, 2015
 
 
 
 
 
 
Beginning balance at July 1, 2015
$
27

$
(165
)
$
(138
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities
 
2

 
(8
)
 
(6
)
Settlements
 
(7
)
 
3

 
(4
)
Ending balance at September 30, 2015
$
22

$
(170
)
$
(148
)
Change in unrealized gains (losses) related to assets/liabilities held at September 30, 2015
$
1

$
(7
)
$
(6
)
For the nine months ended September 30, 2016
 
 
 
 
 
 
Beginning balance at January 1, 2016
$
16

$
(170
)
$
(154
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities
 
(4
)
 
(13
)
 
(17
)
Purchases
 
13

 
—

 
13

Settlements
 
(16
)
 
11

 
(5
)
Ending balance at September 30, 2016
$
9

$
(172
)
$
(163
)
Change in unrealized gains (losses) related to assets/liabilities held at September 30, 2016
$
—

$
(7
)
$
(7
)
For the nine months ended September 30, 2015
 
 
 
 
 
 
Beginning balance at January 1, 2015
$
9

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

 
(37
)
 
(37
)
Purchases
 
29

 
—

 
29

Settlements
 
(16
)
 
9

 
(7
)
Ending balance at September 30, 2015
$
22

$
(170
)
$
(148
)
Change in unrealized gains (losses) related to assets/liabilities held at September 30, 2015
$
1

$
(35
)
$
(34
)

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. For the three and nine months ended September 30, 2016 and 2015, there were no material transfers between Level 1 and Level 2, Level 1 and Level 3, or Level 2 and Level 3 related to derivative commodity contracts.
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 to be 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 September 30, 2016, and December 31, 2015:
 
September 30, 2016
 
December 31, 2015
 
Carrying
Amount
 
Fair
Value
 
Carrying
Amount
 
Fair
Value
Ameren:
 
 
 
 
 
 
 
Long-term debt and capital lease obligations (including current portion)
$
7,038

 
$
7,971

 
$
7,275

 
$
7,814

Preferred stock(a)
142

 
131

 
142

 
125

Ameren Missouri:
 
 
 
 
 
 
 
Long-term debt and capital lease obligations (including current portion)
$
4,000

 
$
4,551

 
$
4,110

 
$
4,449

Preferred stock
80

 
79

 
80

 
75

Ameren Illinois:
 
 
 
 
 
 
 
Long-term debt (including current portion)
$
2,344

 
$
2,682

 
$
2,471

 
$
2,665

Preferred stock
62

 
52

 
62

 
50

(a)
Preferred stock is recorded in “Noncontrolling Interests” on the consolidated balance sheet.
Related Party Transactions
RELATED PARTY TRANSACTIONS
RELATED PARTY TRANSACTIONS
Ameren (parent) and its subsidiaries have engaged in, and may in the future engage in, affiliate transactions in the normal course of business. These transactions primarily consist of power purchases and sales, services received or rendered, and borrowings and lendings.
Transactions between affiliates are reported as intercompany transactions on their respective financial statements but are eliminated in consolidation for Ameren’s financial statements. For a discussion of our material related party agreements, see Note 14 – Related Party Transactions under Part II, Item 8, of the Form 10-K and the money pool arrangements discussed in Note 3 – Short-term Debt and Liquidity of this report.
Electric Power Supply Agreements
In April and September 2016, Ameren Illinois conducted procurement events, administered by the IPA, to purchase energy products. Ameren Missouri was among the winning suppliers in these events. As a result, in April 2016, Ameren Missouri and Ameren Illinois entered into an energy product agreement by which Ameren Missouri agreed to sell, and Ameren Illinois agreed to purchase, 375,200 megawatthours at an average price of $34.71 per megawatthour during the period of June 1, 2017, through September 30, 2018. In September 2016, Ameren Missouri and Ameren Illinois entered into an energy product agreement by which Ameren Missouri agreed to sell, and Ameren Illinois agreed to purchase, 82,800 megawatthours at an average price of $34.35 per megawatthour during the period of May 1, 2017, through September 30, 2018.
The following table presents the impact on Ameren Missouri and Ameren Illinois of related party transactions for the three and nine months ended September 30, 2016 and 2015:
 
 
 
 
Three Months
 
Nine Months
Agreement
Income Statement
Line Item
 
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
Missouri
 
Ameren
Illinois
Ameren Missouri power supply
Operating Revenues
2016
$
9

$
(a)

$
21

$
(a)

agreements with Ameren Illinois
 
2015
 
4

 
(a)

 
9

 
(a)

Ameren Missouri and Ameren Illinois
Operating Revenues
2016
 
5

 
1

 
18

 
3

rent and facility services
 
2015
 
6

 
1

 
19

 
3

Ameren Missouri and Ameren Illinois
Operating Revenues
2016
 
1

 
(b)

 
1

 
(b)

miscellaneous support services
 
2015
 
1

 
(b)

 
2

 
(b)

Total Operating Revenues
 
2016
$
15

$
1

$
40

$
3

 
 
2015
 
11

 
1

 
30

 
3

Ameren Illinois power supply
Purchased Power
2016
$
(a)

$
9

$
(a)

$
21

agreements with Ameren Missouri
 
2015
 
(a)

 
4

 
(a)

 
9

Ameren Illinois transmission
Purchased Power
2016
 
(a)

 
1

 
(a)

 
2

services with ATXI
 
2015
 
(a)

 
1

 
(a)

 
2

Total Purchased Power
 
2016
$
(a)

$
10

$
(a)

$
23

 
 
2015
 
(a)

 
5

 
(a)

 
11

Ameren Services support services
Other Operations and Maintenance
2016
$
30

$
29

$
96

$
90

agreement
 
2015
 
30

 
28

 
96

 
87

Money pool borrowings (advances)
Interest Charges/ Miscellaneous Income
2016
$
(b)

$
(b)

$
(b)

$
(b)

 
 
2015
 
(b)

 
(b)

 
(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 the notes to our financial statements in this report and in our Form 10-K, will not have a material adverse effect on our results of operations, financial position, or liquidity.
Reference is made to Note 1 – Summary of Significant Accounting Policies, Note 2 – Rate and Regulatory Matters, Note 14 – Related Party Transactions, Note 15 – Commitments and Contingencies, and Note 16 – Divestiture Transactions and Discontinued Operations under Part II, Item 8, of the Form 10-K. See also Note 2 – Rate and Regulatory Matters, Note 8 – Related Party Transactions, and Note 10 – Callaway Energy Center.
Callaway Energy Center
The following table presents insurance coverage at Ameren Missouri’s Callaway energy center at September 30, 2016. The property coverage and the nuclear liability coverage renewal dates are April 1 and January 1, respectively, of each year. Both coverages were renewed in 2016.
Type and Source of Coverage
Maximum  Coverages
 
Maximum Assessments
for Single Incidents
 
Public liability and nuclear worker liability:
 
 
 
 
American Nuclear Insurers
$
375

  
$
—

  
Pool participation
12,986

(a) 
127

(b) 
 
$
13,361

(c) 
$
127

  
Property damage:
 
 
 
 
NEIL
$
2,750

(d) 
$
30

(e) 
European Mutual Association for Nuclear Insurance
450

(f) 
—

 
 
$
3,200

 
$
30

 
Replacement power:
 
 
 
 
NEIL
$
490

(g) 
$
7

(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 $2.75 billion in property damage, decontamination, and premature decommissioning insurance for radiation events. NEIL provides $2.3 billion in property damage for nonradiation events.
(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 $450 million in excess of the $2.75 billion and $2.3 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 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 insurance policies, subject to an industrywide aggregate policy 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, or liquidity.
Other Obligations
In order to supply a portion of the fuel requirements of Ameren Missouri’s energy centers, Ameren Missouri has entered into various long-term commitments for the procurement of coal, natural gas, nuclear fuel, and methane gas. Additionally, Ameren Missouri and Ameren Illinois have entered into various long-term commitments for purchased power and natural gas for distribution. At September 30, 2016, total obligations related to commitments for coal, natural gas, nuclear fuel, purchased power, methane gas, equipment, and meter reading services, among other agreements, at Ameren, Ameren Missouri, and Ameren Illinois were $4,328 million, $2,428 million, and $1,859 million, respectively. For additional information regarding our obligations and commitments at December 31, 2015, see Note 15 – Commitments and Contingencies under Part II, Item 8 of the Form 10-K.
In April and September 2016, Ameren Illinois conducted procurement events, administered by the IPA, to purchase energy products and capacity through May 31, 2019. In the April procurement event, Ameren Illinois contracted to purchase approximately 3,609,800 megawatthours of energy products for $105 million from June 1, 2016, through May 31, 2019. In the September procurement event, Ameren Illinois contracted to purchase approximately 2,229,800 megawatthours of energy products for $71 million from October 1, 2016, through May 31, 2019. In addition, in the September procurement event, Ameren Illinois contracted to purchase 1,854 MWs of capacity for $96 million from June 1, 2017, through May 31, 2019. The results of both procurement events are included in Ameren’s and Ameren Illinois’ obligations discussed above. See Note 8 – Related Party Transactions for additional information regarding energy product agreements between Ameren Missouri and Ameren Illinois as a result of these procurement events.
Environmental Matters
We are subject to various environmental laws and regulations enforced by federal, state, and local authorities. Such requirements can impact the siting, development and operation of new and existing generation, transmission, distribution and natural gas storage facilities. Such requirements can encompass emissions, discharges to water, water usage, impacts to air, land, and water, and chemical and waste handling. Complex and lengthy approval processes are required to obtain, modify or renew permits and licenses for new or existing facilities. Additionally, the use and handling of various chemicals or hazardous materials at some of our facilities 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 Ameren Missouri, which operates 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 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, the individual or 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 and their recovery could result in regulatory lag. As of December 31, 2015, Ameren Missouri’s energy centers that emit CO2 represented approximately 20% and 35% of Ameren’s and Ameren Missouri’s rate base, respectively.
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 beyond 2020. This estimate of capital expenditures includes expenditures required for the CCR regulations, the Clean Water Act rule applicable to cooling water intake structures at existing power plants, and the Clean Water Act effluent limitation guidelines applicable to steam electric generating units, all of which are discussed below. This estimate does not include the potential impacts of the Clean Power Plan discussed below. 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 first phase of the CSAPR emission reduction requirements became effective in 2015 and the second phase of emission reduction requirements, which were revised by the EPA in September 2016, will become effective in 2017; additional emission reduction requirements may apply in subsequent years. To achieve compliance with the CSAPR, Ameren Missouri burns ultra-low-sulfur coal, operates two scrubbers at its Sioux energy center, and optimizes other existing pollution control equipment. Ameren Missouri does not expect to make additional capital investments to comply with the 2017 CSAPR requirements. However, Ameren Missouri expects to incur additional costs to lower 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 recovered 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 in August 2015 but stayed by the United States Supreme Court in February 2016, pending the outcome of various legal challenges, as discussed below.
If upheld, the Clean Power Plan would require 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 would require each state to demonstrate progress in achieving its CO2 emissions reduction target. Ameren continues to evaluate 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. 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. All implementation requirements are deferred until such time as these legal challenges are concluded. A decision by the District of Columbia Circuit Court of Appeals is expected to be issued in 2017, and subsequent appeals to the United States Supreme Court are likely. 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 and require Ameren Missouri to make new or accelerated capital expenditures. 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.
In 2015, the EPA also 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 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. A trial was held in the third quarter of 2016. It is not certain when a final decision will be reached in this case, and subsequent appeals are likely. 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 this matter or the costs that might be incurred.
Clean Water Act
In 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. Additionally, in 2015, the EPA issued its final rule 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 waste streams and imposes more stringent limitations on certain components in water discharges from power plants. All of Ameren Missouri’s coal-fired and nuclear energy centers are subject to the cooling water intake structures rule and all of Ameren Missouri’s coal-fired energy centers are subject to the effluent limitations rule. Implementation of both rules will occur during the renewal process of each energy center’s water discharge permit, which will occur between 2018 and 2023. The rules could have an adverse effect on Ameren’s and Ameren Missouri’s results of operations, financial position, and liquidity if their implementation requires extensive modifications to the cooling water systems and water discharge systems at Ameren Missouri’s energy centers and if those investments are not recovered on a timely basis in electric rates charged to Ameren Missouri’s customers.
Ash Management
In 2015, the EPA issued regulations regarding the management and disposal of CCR. These regulations affect 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, which could reduce the amount to be disposed. The regulations also establish criteria regarding the structural integrity, location, groundwater monitoring, and operation of CCR impoundments and landfills. They require closure of impoundments if the criteria are not achieved. 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.
Remediation
The Ameren Companies are involved in a number of remediation actions to clean up sites impacted by the use or disposal of materials containing hazardous substances. Federal and state laws can require responsible parties to 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 September 30, 2016, 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 review by the ICC. As of September 30, 2016, Ameren Illinois estimated the obligation related to these former MGP sites at $204 million to $274 million. Ameren and Ameren Illinois recorded a liability of $204 million to represent the estimated minimum obligation for these sites, as no other amount within the range was a better estimate.
The scope of the remediation activities at these former MGP sites may increase as remediation efforts continue. Considerable uncertainty remains in these estimates because many site-specific factors can influence the ultimate actual costs, including 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 Missouri participated in the investigation of various sites known as Sauget Area 2 located in Sauget, Illinois. In 2000, the EPA notified Ameren Missouri and numerous other companies that former landfills and lagoons at those sites may contain soil and groundwater contamination. 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 by others as a landfill.
In December 2013, the EPA issued its record of decision for Sauget Area 2 approving the investigation and the remediation actions 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 September 30, 2016, 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 for this site, as no other amount within the range was a better estimate.
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.
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, including revenues from wholesale power and interchange sales. Ameren and Ameren Missouri recorded immaterial liabilities on their respective balance sheets as of September 30, 2016, and December 31, 2015, representing their estimate of the probable loss due as a result of this lawsuit. Ameren and Ameren Missouri believe there is a remote possibility that a liability relating to this lawsuit could be material to Ameren and Ameren Missouri’s results of operations, financial position, and liquidity. 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.
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 and other utilities that own and operate those 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, which stated that the DOE would begin to dispose of spent nuclear fuel by 1998, 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 was suspended in May 2014. 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.
As a result of the DOE's failure to fulfill its contractual obligations, Ameren Missouri and other nuclear energy center owners sued the DOE to recover costs, such as certain NRC fees and ad valorem taxes, incurred for ongoing storage of their spent fuel. The lawsuit resulted in a settlement agreement that provides for annual reimbursement of additional spent fuel storage and related costs. 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. In April 2016, the MoPSC approved no change in electric service rates for decommissioning costs based on Ameren Missouri’s updated cost study and funding analysis filed in April 2015.
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. If the assumed return on trust assets is not earned, Ameren Missouri believes that it is probable that any such earnings deficiency will be recovered in rates.
Retirement Benefits
RETIREMENT BENEFITS
RETIREMENT BENEFITS
The following table presents the components of the net periodic benefit cost (benefit) incurred for Ameren’s pension and postretirement benefit plans for the three and nine months ended September 30, 2016 and 2015:
  
Pension Benefits
 
Postretirement Benefits
 
 
Three Months
 
Nine Months
 
Three Months
 
Nine Months
 
  
2016
 
2015
 
2016
 
2015
 
2016
 
2015
 
2016
 
2015
 
Service cost
$
20

 
$
23

 
$
60

 
$
69

 
$
5

 
$
6

 
$
15

 
$
17

 
Interest cost
46

 
43

 
138

 
130

 
12

 
12

 
36

 
36

 
Expected return on plan assets
(63
)
 
(62
)
 
(189
)
 
(186
)
 
(18
)
 
(17
)
 
(54
)
 
(51
)
 
Amortization of:
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Prior service benefit
—

 
—

 
—

 
—

 
(1
)
 
(1
)
 
(3
)
 
(3
)
 
Actuarial loss (gain)
8

 
19

 
24

 
56

 
(3
)
 
1

 
(8
)
 
4

 
Settlement loss
—

 
—

 
—

 
1

 
—

 
—

 
—

 
—

 
Net periodic benefit cost (benefit)
$
11

 
$
23

 
$
33

 
$
70

 
$
(5
)
 
$
1

 
$
(14
)
 
$
3

 

Ameren Missouri and Ameren Illinois are responsible for their respective shares of Ameren’s pension and postretirement costs. The following table presents the pension costs and the postretirement benefit costs (benefit) incurred for the three and nine months ended September 30, 2016 and 2015:
  
Pension Benefits
 
Postretirement Benefits
 
 
Three Months
 
Nine Months
 
Three Months
 
Nine Months
 
  
2016
 
2015
 
2016
 
2015
 
2016
 
2015
 
2016
 
2015
 
Ameren Missouri(a)
$
6

 
$
14

 
$
19

 
$
42

 
$
(1
)
 
$
2

 
$
(3
)
 
$
6

 
Ameren Illinois
6

 
9

 
17

 
28

 
(3
)
 
—

 
(10
)
 
(2
)
 
Other
(1
)
 
—

 
(3
)
 
—

 
(1
)
 
(1
)
 
(1
)
 
(1
)
 
Ameren(a)(b)
$
11

 
$
23

 
$
33

 
$
70

 
$
(5
)
 
$
1

 
$
(14
)
 
$
3

 

(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 registrants and nonregistrant subsidiaries.
Divestiture Transactions and Discontinued Operations
DIVESTITURE TRANSACTIONS AND DISCONTINUED OPERATIONS
DISCONTINUED OPERATIONS
There was no net income attributable to Ameren common shareholders from discontinued operations during 2016. The following table presents the components of discontinued operations in Ameren's consolidated statement of income for the three and nine months ended September 30, 2015:
 
2015
 
2015
 
Three Months
 
Nine Months
Operating revenues
$
—

 
$
—

Operating benefits (expenses)
(1
)
 
2

Operating income (loss) before income tax
(1
)
 
2

Income tax benefit
1

 
50

Income from discontinued operations, net of taxes
$
—

 
$
52

During the second quarter of 2015, based on the completion of the IRS audit for 2013, Ameren removed a previously recorded reserve for unrecognized tax benefits and recognized a tax benefit from discontinued operations. See Note 16 – Divestiture Transactions and Discontinued Operations under Part II, Item 8, of the Form 10-K for additional information related to discontinued operations.
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 September 30, 2016, and December 31, 2015:
 
September 30, 2016
 
December 31, 2015
Assets of discontinued operations
 
 
 
Accumulated deferred income taxes, net
$
15

 
$
14

Total assets of discontinued operations
$
15

 
$
14

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

 
$
1

Asset retirement obligations(a)
26

 
28

Total liabilities of discontinued operations
$
27

 
$
29

(a)
Ameren has completed its retirement obligations at the Hutsonville energy center. The remaining ARO liabilities relate to the abandoned Meredosia energy center.
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 of the operations of Ameren Missouri’s business as described in Note 1 – Summary of Significant Accounting Policies. The Ameren Illinois segment for both Ameren and Ameren Illinois includes all of the operations of Ameren Illinois’ business 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 following table presents information about the reported revenues and net income attributable to Ameren common shareholders from continuing operations for the three and nine months ended September 30, 2016 and 2015, and total assets of continuing operations as of September 30, 2016, and December 31, 2015:
Three Months
Ameren
Missouri
 
Ameren
Illinois
 
Other
 
Intersegment
Eliminations
 
Ameren
 
2016
 
 
 
 
 
 
 
 
 
 
External revenues
$
1,150

 
$
675

 
$
34

  
$
—

 
$
1,859

 
Intersegment revenues
15

 
1

 
1

  
(17
)
 
—

 
Net income attributable to Ameren common shareholders from continuing operations
241

 
119

 
9

 
—

 
369

 
2015
 
 
 
 
 
 
 
 
 
 
External revenues
$
1,160

 
$
654

 
$
19

 
$
—

 
$
1,833

 
Intersegment revenues
11

 
1

 
1

 
(13
)
 
—

 
Net income attributable to Ameren common shareholders from continuing operations
239

 
98

 
6

 
—

 
343

 
Nine Months
  
 
  
 
  
 
  
 
  
 
2016
 
 
 
 
 
 
 
 
 
 
External revenues
$
2,733

 
$
1,892

 
$
95

 
$
—

 
$
4,720

 
Intersegment revenues
40

 
3

 
2

 
(45
)
 
—

 
Net income attributable to Ameren common shareholders from continuing operations
347

 
223

 
51

 
—

 
621

 
2015
 
 
 
 
 
 
 
 
 
 
External revenues
$
2,825

 
$
1,910

 
$
55

 
$
—

 
$
4,790

 
Intersegment revenues
30

 
3

 
2

 
(35
)
 
—

 
Net income attributable to Ameren common shareholders from continuing operations
341

 
182

 
26

 
—

 
549

 
As of September 30, 2016:
 
 
 
 
 
 
 
 
 
 
Total assets
$
13,889

 
$
9,202

 
$
1,496

 
$
(468
)
 
$
24,119

(a) 
As of December 31, 2015:
 
 
 
 
 
 
 
 
 
 
Total assets
$
13,851

 
$
8,903

 
$
1,139

 
$
(267
)
 
$
23,626

(a) 
(a)    Excludes total assets from discontinued operations of $15 million and $14 million as of September 30, 2016, and December 31, 2015, respectively.
Summary Of Significant Accounting Policies (Policies)
Consolidation 
Ameren’s financial statements are prepared on a consolidated basis and therefore include the accounts of its majority-owned subsidiaries. All intercompany transactions have been eliminated. Ameren Missouri and Ameren Illinois have no subsidiaries, and therefore their financial statements are not prepared on a consolidated basis. 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 statement 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. The results of operations of an interim period may not give a true indication of results that may be expected for a full year. These financial statements should be read in conjunction with the financial statements and the notes thereto included in the Form 10-K.
Excise Taxes 
Excise taxes are levied on Ameren Missouri’s electric and natural gas businesses and on Ameren Illinois’ natural gas business and 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 the customer and are therefore not included in Ameren Illinois’ revenues and expenses.
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.
Accounting and Reporting Developments 
Below is a summary of recently issued authoritative accounting standards relevant to 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 impact 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. The guidance will be effective for the Ameren Companies in the first quarter of 2018.
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, similar legal entities, and certain investment funds, (2) the evaluation of fees paid to a decision maker or service provider as a variable interest, (3) how fee arrangements impact the primary beneficiary determination, and (4) the evaluation of related party relationships on the primary beneficiary determination. The adoption of this guidance in the first quarter of 2016 did not impact the Ameren Companies’ results of operations, financial position, liquidity, or disclosures.
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, with an option for entities to adopt early. Upon adoption, the Ameren Companies will recognize and measure operating leases on their respective balance sheets at the beginning of the earliest period presented. The Ameren Companies are currently assessing the impact of this guidance on their results of operations, financial position, statement of cash flows, and disclosures.
Improvements to Employee Share-Based Payment Accounting
In March 2016, the FASB issued authoritative accounting guidance that simplifies the accounting for share-based payment transactions, including the income tax consequences, the calculation of diluted earnings per share, the treatment of forfeitures, the classification of awards as either equity or liabilities, and the classification on the statement of cash flows. Ameren determines for each performance share unit award whether the difference between the deduction for tax purposes and the compensation cost recognized for financial reporting purposes results in either an excess tax benefit or an excess tax deficit. Previously, excess tax benefits were recognized in "Other paid-in capital" on Ameren’s consolidated balance sheet, and in certain cases, excess tax deficits were recognized in “Income taxes” on Ameren’s consolidated income statement. The new guidance increases income statement volatility by requiring all excess tax benefits and deficits to be recognized in “Income taxes,” and treated as discrete items in the period in which they occur. Ameren adopted this guidance in the first quarter of 2016 and prospectively applied the amendment in this guidance requiring recognition of excess tax benefits and deficits in the income statement, which resulted in recognition of a $21 million income tax benefit and a corresponding $21 million increase in income from continuing operations and net income (9 cents per diluted share) during that period. Also as a result of the adoption of this guidance, Ameren made an accounting policy election to continue to estimate the number of forfeitures expected to occur. The amendments in the guidance that require application using a modified retrospective transition method did not impact Ameren. Therefore, there was no cumulative-effect adjustment to retained earnings recognized as of January 1, 2016. Ameren applied the amendments in this guidance relating to classification on the statement of cash flows retrospectively. As a result, for the nine months ended September 30, 2015, Ameren reclassified, for comparison purposes, $2 million of excess tax benefits on the statement of cash flows from financing to operating activity, and $12 million of employee payroll taxes related to share-based payments from operating to financing activity.
Derivative Financial Instruments Derivative Financial Instruments (Policies)
Derivatives
•
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.
Summary Of Significant Accounting Policies (Tables)
Summary Of Nonvested Shares Related To Long-Term Incentive Plan 
A summary of nonvested performance share units at September 30, 2016, and changes during the nine months ended September 30, 2016, 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, 2016
1,024,870

 
$
46.08

Granted(a)
587,197

 
44.13

Forfeitures
(15,949
)
 
45.07

Vested(b)
(23,114
)
 
44.41

Nonvested at September 30, 2016
1,573,004

 
$
45.39

(a)
Performance share units granted to certain executive and nonexecutive officers and other eligible employees under the 2014 Incentive Plan.
(b)
Performance share units vested due to the 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.
Schedule of Excise Taxes 
The following table presents excise taxes recorded in “Operating Revenues – Electric,” “Operating Revenues – Gas” and “Operating Expenses – Taxes other than income taxes” for the three and nine months ended September 30, 2016 and 2015:
 
Three Months
 
Nine Months
 
2016
 
2015
 
2016
 
2015
Ameren Missouri
$
52

 
$
52

 
$
122

 
$
127

Ameren Illinois
9

 
9

 
40

 
42

Ameren
$
61

 
$
61

 
$
162

 
$
169

Short-Term Debt And Liquidity Short-Term Debt and Liquidity (Tables)
Schedule of Short-term Debt
The following table presents commercial paper outstanding as of September 30, 2016, and December 31, 2015:
  
2016
 
2015
Ameren (parent)
$
451

 
$
301

Ameren Missouri
—

 
—

Ameren Illinois
157

 
—

Ameren Consolidated
$
608

 
$
301

The following table summarizes the borrowing activity and relevant interest rates under Ameren’s (parent), Ameren Missouri’s, and Ameren Illinois’ commercial paper programs for the nine months ended September 30, 2016 and 2015:
 
 
Ameren
(parent)
Ameren
Missouri
Ameren
Illinois
Ameren Consolidated
2016
 
 
 
 
 
 
Average daily commercial paper outstanding
 
$
435

 
$
80

$
48

$
563

Weighted-average interest rate
 
0.81
%
 
0.74
%
0.72
%
0.79
%
Peak commercial paper during period(a)
 
$
574

 
$
208

$
195

$
839

Peak interest rate
 
0.95
%
 
0.85
%
0.85
%
0.95
%
2015
 
 
 
 
 
 
Average daily commercial paper outstanding
 
$
770

 
$
56

$
6

$
832

Weighted-average interest rate
 
0.56
%
 
0.50
%
0.44
%
0.56
%
Peak commercial paper during period(a)
 
$
874

 
$
294

$
48

$
1,108

Peak interest rate
 
0.70
%
 
0.60
%
0.60
%
0.70
%

(a)
The timing of peak commercial paper issuances varies by company; 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 Coverage Ratios
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 first mortgage bonds or preferred stock. The following table summarizes the required and actual interest coverage ratios for interest charges, dividend coverage ratios, and first mortgage bonds and preferred stock issuable as of September 30, 2016, at an assumed annual 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
 
4.7
$
3,838
 
≥2.5
 
105.9
$
2,357
 
Ameren Illinois
 
≥2.0
 
7.3
 
3,942
(d) 
≥1.5
 
3.0
 
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 first mortgage bonds issuable based either on required coverage ratios or unfunded property additions, whichever is more restrictive. The amounts shown also include first mortgage bonds issuable based on retired bond capacity of $1,206 million and $279 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 first mortgage bonds issuable by Ameren Illinois based on unfunded property additions and retired bonds solely under the former IP mortgage indenture. The amount of first mortgage 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.
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 for the three and nine months ended September 30, 2016 and 2015:
 
Three Months
 
Nine Months
 
 
2016
 
2015
 
2016
 
2015
 
Ameren:(a)
 
 
 
 
 
 
 
 
Miscellaneous income:
 
 
 
 
 
 
 
 
Allowance for equity funds used during construction
$
7

 
$
8

 
$
20

 
$
19

 
Interest income on industrial development revenue bonds
7

 
7

 
20

 
20

 
Interest income
3

 
4

 
11

 
12

 
Other
1

 
—

 
3

 
3

 
Total miscellaneous income
$
18

 
$
19

 
$
54

 
$
54

 
Miscellaneous expense:
 
 
 
 
 
 
 
 
Donations
$
1

 
$
—

 
$
8

 
$
10

 
Other
7

 
5

 
13

 
12

 
Total miscellaneous expense
$
8

 
$
5

 
$
21

 
$
22

 
Ameren Missouri:
 
 
 
 
 
 
 
 
Miscellaneous income:
 
 
 
 
 
 
 
 
Allowance for equity funds used during construction
$
6

 
$
7

 
$
16

 
$
16

 
Interest income on industrial development revenue bonds
7

 
7

 
20

 
20

 
Interest income
1

 
—

 
1

 
1

 
Other
—

 
—

 
1

  
—

 
Total miscellaneous income
$
14

 
$
14

 
$
38

 
$
37

 
Miscellaneous expense:
 
 
 
 
 
 
 
 
Donations
$
—

 
$
—

 
$
2

 
$
3

 
Other
2

 
3

 
4

 
5

 
Total miscellaneous expense
$
2

 
$
3

 
$
6

 
$
8

 
 
Three Months
 
Nine Months
 
 
2016
 
2015
 
2016
 
2015
 
Ameren Illinois:
 
 
 
 
 
 
 
 
Miscellaneous income:
 
 
 
 
 
 
 
 
Allowance for equity funds used during construction
$
1

 
$
1

 
$
4

 
$
3

 
Interest income
2

 
3

 
9

 
10

 
Other
1

 
—

 
2

 
2

 
Total miscellaneous income
$
4

 
$
4

 
$
15

 
$
15

 
Miscellaneous expense:
 
 
 
 
 
 
 
 
Donations
$
1

 
$
—

 
$
6

 
$
4

 
Other
2

 
3

 
5

 
6

 
Total miscellaneous expense
$
3

 
$
3

 
$
11

 
$
10

 
(a)
Includes amounts for Ameren registrant and nonregistrant subsidiaries and intercompany eliminations.
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 September 30, 2016, and December 31, 2015. As of September 30, 2016, these contracts extended through October 2018, March 2021, May 2032, and February 2020 for fuel oils, natural gas, power, and uranium, respectively.
  
Quantity (in millions, except as indicated)
 
2016
2015
Commodity
Ameren Missouri
Ameren Illinois
Ameren
Ameren Missouri
Ameren Illinois
Ameren
Fuel oils (in gallons)(a)
25

(b)

25

35

(b)

35

Natural gas (in mmbtu)
26

128

154

30

151

181

Power (in megawatthours)
1

9

10

1

10

11

Uranium (pounds in thousands)
445

(b)

445

494

(b)

494

(a)
Consists of ultra-low-sulfur diesel products.
(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 September 30, 2016, and December 31, 2015:
 
Balance Sheet Location
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
2016
 
 
 
 
 
 
Fuel oils
Other assets
 
$
1

 
$
—

 
$
1

Natural gas
Other current assets
 
—

 
2

 
2

 
Other assets
 
—

 
1

 
1

Power
Other current assets
 
11

 
—

 
11

 
Total assets (a)
 
$
12

 
$
3

 
$
15

Fuel oils
Other current liabilities
 
$
8

 
$
—

 
$
8

 
Other deferred credits and liabilities
 
1

 
—

 
1

Natural gas
MTM derivative liabilities
 
(b)

 
9

 
(b)

 
Other current liabilities
 
3

 
—

 
12

 
Other deferred credits and liabilities
 
6

 
9

 
15

Power
MTM derivative liabilities
 
(b)

 
12

 
(b)

 
Other current liabilities
 
2

 
—

 
14

 
Other deferred credits and liabilities
 
—

 
160

 
160

Uranium
Other current liabilities
 
2

 
—

 
2

 
Other deferred credits and liabilities
 
3

 
—

 
3

 
Total liabilities (c)
 
$
25

 
$
190

 
$
215

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


(a)
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)
The cumulative amount of pretax net losses on all derivative instruments is deferred as a regulatory asset.
Offsetting Derivative Assets and Liabilities 
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 September 30, 2016, and December 31, 2015:
 
 
 
 
Gross Amounts Not Offset in the Balance Sheet
 
 
Commodity Contracts Eligible to be Offset
 
Gross Amounts Recognized in the Balance Sheet
 
Derivative Instruments
 
Cash Collateral Received/Posted(a)
 
Net
Amount
2016
 
 
 
 
 
 
 
 
Assets:
 
 
 
 
 
 
 
 
Ameren Missouri
 
$
12

 
$
2

 
$
—

 
$
10

Ameren Illinois
 
3

 
2

 
—

 
1

Ameren
 
$
15

 
$
4

 
$
—

 
$
11

Liabilities:
 
 
 
 
 
 
 
 
Ameren Missouri
 
$
25

 
$
2

 
$
5

 
$
18

Ameren Illinois
 
190

 
2

 
—

 
188

Ameren
 
$
215

 
$
4

 
$
5

 
$
206

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

(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.
Derivative Instruments With Credit Risk-Related Contingent Features 
The following table presents, as of September 30, 2016, 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 September 30, 2016, 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)
2016
 
 
 
 
 
Ameren Missouri
$
69

 
$
2

 
$
60

Ameren Illinois
53

 
—

 
46

Ameren
$
122

 
$
2

 
$
106

(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 (Tables)
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis, Valuation Techniques 
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 September 30, 2016, and December 31, 2015:
 
 
Fair Value
 
 
 
Weighted Average
 
 
Assets
Liabilities
Valuation Technique(s)
Unobservable Input
Range
Level 3 Derivative asset and liability – commodity contracts(a):
 
 
 
2016
 
 
 
 
 
 
 
 
Fuel oils
$
1

$
—

Option model
Volatilities(%)(b)
25 – 38
26
 
 
 
 
Discounted cash flow
Counterparty credit risk(%)(c)(d)
0.22
(e)
 
 
 
 
 
Ameren Missouri credit risk(%)(c)(d)
0.38
(d)
 
Power(f)
11

(174
)
Discounted cash flow
Average forward peak and off-peak pricing – forwards/swaps ($/MWh)(g)
25 – 42
29
 
 
 
 
 
Estimated auction price for FTRs ($/MW)(b)
(253) – 3,593
31
 
 
 
 
 
Nodal basis ($/MWh)(g)
(6) – 0
(2)
 
 
 
 
 
Ameren credit risk (%)(c)(d)
0.38
(e)
 
 
 
 
Fundamental energy production model
Estimated future gas prices ($/mmbtu)(b)
3 – 5
4
 
 
 
 
 
Escalation rate (%)(b)(h)
4
(e)
 
 
 
 
Contract price allocation
Estimated renewable energy credit costs ($/credit)(b)
5 – 7
6
 
Uranium
—

(5
)
Option model
Volatilities (%)(b)
20
(e)
 
 
 
 
Discounted cash flow
Average forward uranium pricing ($/pound)(b)
22 – 26
24
 
 
 
 
 
Ameren Missouri credit risk (%)(c)(d)
0.38
(e)
 
 
Fair Value
 
 
 
Weighted Average
 
 
Assets
Liabilities
Valuation Technique(s)
Unobservable Input
Range
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)
 
 
 
 
 
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)

(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 2020. Valuations beyond 2020 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 due to their opposing positions.
(h)
Escalation rate applies to power prices in 2031 and beyond for September 30, 2016, and to power prices in 2026 and beyond for December 31, 2015.
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 September 30, 2016:
 
 
 
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
 
$
—

 
$
—

 
$
1

 
$
1

 
 
Natural gas
 
$
—

 
$
3

 
$
—

 
$
3

 
 
Power
 
—

 
—

 
11

 
11

 
 
Total derivative assets – commodity contracts
 
$
—

 
$
3

 
$
12

 
$
15

 
 
Nuclear decommissioning trust fund:
 
 
 
 
 
 
 
 
 
 
Cash and cash equivalents
 
$
3

 
$
—

 
$
—

 
$
3

 
 
Equity securities:
 
 
 
 
 
 
 
 
 
 
U.S. large capitalization
 
393

 
—

 
—

 
393

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

 
120

 
—

 
120

 
 
Corporate bonds
 
—

 
64

 
—

 
64

 
 
Other
 
—

 
17

 
—

 
17

 
 
Total nuclear decommissioning trust fund
 
$
396

 
$
201

 
$
—

 
$
597

(b) 
 
Total Ameren
 
$
396

 
$
204

 
$
12

 
$
612

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

 
$
—

 
$
1

 
$
1

 
 
Power
 
—

 
—

 
11

 
11

 
 
Total derivative assets – commodity contracts
 
$
—

 
$
—

 
$
12

 
$
12

 
 
Nuclear decommissioning trust fund:
 
 
 
 
 
 
 
 
 
 
Cash and cash equivalents
 
$
3

 
$
—

 
$
—

 
$
3

 
 
Equity securities:
 
 
 
 
 
 
 
 
 
 
U.S. large capitalization
 
393

 
—

 
—

 
393

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

 
120

 
—

 
120

 
 
Corporate bonds
 
—

 
64

 
—

 
64

 
 
Other
 
—

 
17

 
—

 
17

 
 
Total nuclear decommissioning trust fund
 
$
396

 
$
201

 
$
—

 
$
597

(b) 
 
Total Ameren Missouri
 
$
396

 
$
201

 
$
12

 
$
609

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

 
$
3

 
$
—

 
$
3

 
Liabilities:
 
 
 
 
 
 
 
 
 
 
Ameren
Derivative liabilities – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
9

 
$
—

 
$
—

 
$
9

 
 
Natural gas
 
—

 
27

 
—

 
27

 
 
Power
 
—

 
—

 
174

 
174

 
 
Uranium
 
—

 
—

 
5

 
5

 
 
Total Ameren
 
$
9

 
$
27

 
$
179

 
$
215

 
Ameren
Derivative liabilities – commodity contracts(a):
 
 
 
 
 
 
 
 
 
Missouri
Fuel oils
 
$
9

 
$
—

 
$
—

 
$
9

 
 
Natural gas
 
—

 
9

 
—

 
9

 
 
Power
 
—

 
—

 
2

 
2

 
 
Uranium
 
—

 
—

 
5

 
5

 
 
Total Ameren Missouri
 
$
9

 
$
9

 
$
7

 
$
25

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

 
$
18

 
$
—

 
$
18

 
 
Power
 
—

 
—

 
172

 
172

 
 
Total Ameren Illinois
 
$
—

 
$
18

 
$
172

 
$
190

 
(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 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
Derivative assets – commodity contracts(a):
 
 
 
 
 
 
 
 
 
Missouri
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
Derivative assets – commodity contracts(a):
 
 
 
 
 
 
 
 
 
Illinois
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

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

 
$
—

 
$
—

 
$
29

 
 
Natural gas
 
—

 
13

 
1

 
14

 
 
Uranium
 
—

 
—

 
1

 
1

 
 
Total Ameren Missouri
 
$
29

 
$
13

 
$
2

 
$
44

 
Ameren
Derivative liabilities – commodity contracts(a):
 
 
 
 
 
 
 
 
 
Illinois
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.
Schedule Of Changes In The Fair Value Of Financial Assets And Liabilities Classified As Level Three In The Fair Value Hierarchy 
The following table summarizes the changes in the fair value of power financial assets and liabilities classified as Level 3 in the fair value hierarchy:
  
 
Net derivative commodity contracts
 
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
For the three months ended September 30, 2016
 
 
 
 
 
 
Beginning balance at July 1, 2016
$
14

$
(169
)
$
(155
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities
 
—

 
(6
)
 
(6
)
Settlements
 
(5
)
 
3

 
(2
)
Ending balance at September 30, 2016
$
9

$
(172
)
$
(163
)
Change in unrealized gains (losses) related to assets/liabilities held at September 30, 2016
$
—

$
(2
)
$
(2
)
For the three months ended September 30, 2015
 
 
 
 
 
 
Beginning balance at July 1, 2015
$
27

$
(165
)
$
(138
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities
 
2

 
(8
)
 
(6
)
Settlements
 
(7
)
 
3

 
(4
)
Ending balance at September 30, 2015
$
22

$
(170
)
$
(148
)
Change in unrealized gains (losses) related to assets/liabilities held at September 30, 2015
$
1

$
(7
)
$
(6
)
For the nine months ended September 30, 2016
 
 
 
 
 
 
Beginning balance at January 1, 2016
$
16

$
(170
)
$
(154
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities
 
(4
)
 
(13
)
 
(17
)
Purchases
 
13

 
—

 
13

Settlements
 
(16
)
 
11

 
(5
)
Ending balance at September 30, 2016
$
9

$
(172
)
$
(163
)
Change in unrealized gains (losses) related to assets/liabilities held at September 30, 2016
$
—

$
(7
)
$
(7
)
For the nine months ended September 30, 2015
 
 
 
 
 
 
Beginning balance at January 1, 2015
$
9

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

 
(37
)
 
(37
)
Purchases
 
29

 
—

 
29

Settlements
 
(16
)
 
9

 
(7
)
Ending balance at September 30, 2015
$
22

$
(170
)
$
(148
)
Change in unrealized gains (losses) related to assets/liabilities held at September 30, 2015
$
1

$
(35
)
$
(34
)

Schedule Of Carrying Amounts And Estimated Fair Values Of Long-Term Debt, Capital Lease Obligations And Preferred Stock 
The following table presents the carrying amounts and estimated fair values of our long-term debt, capital lease obligations and preferred stock at September 30, 2016, and December 31, 2015:
 
September 30, 2016
 
December 31, 2015
 
Carrying
Amount
 
Fair
Value
 
Carrying
Amount
 
Fair
Value
Ameren:
 
 
 
 
 
 
 
Long-term debt and capital lease obligations (including current portion)
$
7,038

 
$
7,971

 
$
7,275

 
$
7,814

Preferred stock(a)
142

 
131

 
142

 
125

Ameren Missouri:
 
 
 
 
 
 
 
Long-term debt and capital lease obligations (including current portion)
$
4,000

 
$
4,551

 
$
4,110

 
$
4,449

Preferred stock
80

 
79

 
80

 
75

Ameren Illinois:
 
 
 
 
 
 
 
Long-term debt (including current portion)
$
2,344

 
$
2,682

 
$
2,471

 
$
2,665

Preferred stock
62

 
52

 
62

 
50

(a)
Preferred stock is recorded in “Noncontrolling Interests” on the consolidated balance sheet.
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 three and nine months ended September 30, 2016 and 2015:
 
 
 
 
Three Months
 
Nine Months
Agreement
Income Statement
Line Item
 
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
Missouri
 
Ameren
Illinois
Ameren Missouri power supply
Operating Revenues
2016
$
9

$
(a)

$
21

$
(a)

agreements with Ameren Illinois
 
2015
 
4

 
(a)

 
9

 
(a)

Ameren Missouri and Ameren Illinois
Operating Revenues
2016
 
5

 
1

 
18

 
3

rent and facility services
 
2015
 
6

 
1

 
19

 
3

Ameren Missouri and Ameren Illinois
Operating Revenues
2016
 
1

 
(b)

 
1

 
(b)

miscellaneous support services
 
2015
 
1

 
(b)

 
2

 
(b)

Total Operating Revenues
 
2016
$
15

$
1

$
40

$
3

 
 
2015
 
11

 
1

 
30

 
3

Ameren Illinois power supply
Purchased Power
2016
$
(a)

$
9

$
(a)

$
21

agreements with Ameren Missouri
 
2015
 
(a)

 
4

 
(a)

 
9

Ameren Illinois transmission
Purchased Power
2016
 
(a)

 
1

 
(a)

 
2

services with ATXI
 
2015
 
(a)

 
1

 
(a)

 
2

Total Purchased Power
 
2016
$
(a)

$
10

$
(a)

$
23

 
 
2015
 
(a)

 
5

 
(a)

 
11

Ameren Services support services
Other Operations and Maintenance
2016
$
30

$
29

$
96

$
90

agreement
 
2015
 
30

 
28

 
96

 
87

Money pool borrowings (advances)
Interest Charges/ Miscellaneous Income
2016
$
(b)

$
(b)

$
(b)

$
(b)

 
 
2015
 
(b)

 
(b)

 
(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 September 30, 2016. The property coverage and the nuclear liability coverage renewal dates are April 1 and January 1, respectively, of each year. Both coverages were renewed in 2016.
Type and Source of Coverage
Maximum  Coverages
 
Maximum Assessments
for Single Incidents
 
Public liability and nuclear worker liability:
 
 
 
 
American Nuclear Insurers
$
375

  
$
—

  
Pool participation
12,986

(a) 
127

(b) 
 
$
13,361

(c) 
$
127

  
Property damage:
 
 
 
 
NEIL
$
2,750

(d) 
$
30

(e) 
European Mutual Association for Nuclear Insurance
450

(f) 
—

 
 
$
3,200

 
$
30

 
Replacement power:
 
 
 
 
NEIL
$
490

(g) 
$
7

(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 $2.75 billion in property damage, decontamination, and premature decommissioning insurance for radiation events. NEIL provides $2.3 billion in property damage for nonradiation events.
(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 $450 million in excess of the $2.75 billion and $2.3 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 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.
Retirement Benefits (Tables)
Components Of Net Periodic Benefit Cost 
The following table presents the components of the net periodic benefit cost (benefit) incurred for Ameren’s pension and postretirement benefit plans for the three and nine months ended September 30, 2016 and 2015:
  
Pension Benefits
 
Postretirement Benefits
 
 
Three Months
 
Nine Months
 
Three Months
 
Nine Months
 
  
2016
 
2015
 
2016
 
2015
 
2016
 
2015
 
2016
 
2015
 
Service cost
$
20

 
$
23

 
$
60

 
$
69

 
$
5

 
$
6

 
$
15

 
$
17

 
Interest cost
46

 
43

 
138

 
130

 
12

 
12

 
36

 
36

 
Expected return on plan assets
(63
)
 
(62
)
 
(189
)
 
(186
)
 
(18
)
 
(17
)
 
(54
)
 
(51
)
 
Amortization of:
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Prior service benefit
—

 
—

 
—

 
—

 
(1
)
 
(1
)
 
(3
)
 
(3
)
 
Actuarial loss (gain)
8

 
19

 
24

 
56

 
(3
)
 
1

 
(8
)
 
4

 
Settlement loss
—

 
—

 
—

 
1

 
—

 
—

 
—

 
—

 
Net periodic benefit cost (benefit)
$
11

 
$
23

 
$
33

 
$
70

 
$
(5
)
 
$
1

 
$
(14
)
 
$
3

 

Summary Of Benefit Plan Costs Incurred 
Ameren Missouri and Ameren Illinois are responsible for their respective shares of Ameren’s pension and postretirement costs. The following table presents the pension costs and the postretirement benefit costs (benefit) incurred for the three and nine months ended September 30, 2016 and 2015:
  
Pension Benefits
 
Postretirement Benefits
 
 
Three Months
 
Nine Months
 
Three Months
 
Nine Months
 
  
2016
 
2015
 
2016
 
2015
 
2016
 
2015
 
2016
 
2015
 
Ameren Missouri(a)
$
6

 
$
14

 
$
19

 
$
42

 
$
(1
)
 
$
2

 
$
(3
)
 
$
6

 
Ameren Illinois
6

 
9

 
17

 
28

 
(3
)
 
—

 
(10
)
 
(2
)
 
Other
(1
)
 
—

 
(3
)
 
—

 
(1
)
 
(1
)
 
(1
)
 
(1
)
 
Ameren(a)(b)
$
11

 
$
23

 
$
33

 
$
70

 
$
(5
)
 
$
1

 
$
(14
)
 
$
3

 

(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 registrants and nonregistrant subsidiaries.
Divestiture Transactions and Discontinued Operations Divestiture Transactions and Discontinued Operations (Tables)
Schedule of Disposal Groups, Including Discontinued Operations Income Staement, balance Sheet and Additional Disclosures
The following table presents the components of discontinued operations in Ameren's consolidated statement of income for the three and nine months ended September 30, 2015:
 
2015
 
2015
 
Three Months
 
Nine Months
Operating revenues
$
—

 
$
—

Operating benefits (expenses)
(1
)
 
2

Operating income (loss) before income tax
(1
)
 
2

Income tax benefit
1

 
50

Income from discontinued operations, net of taxes
$
—

 
$
52

During the second quarter of 2015, based on the completion of the IRS audit for 2013, Ameren removed a previously recorded reserve for unrecognized tax benefits and recognized a tax benefit from discontinued operations. See Note 16 – Divestiture Transactions and Discontinued Operations under Part II, Item 8, of the Form 10-K for additional information related to discontinued operations.
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 September 30, 2016, and December 31, 2015:
 
September 30, 2016
 
December 31, 2015
Assets of discontinued operations
 
 
 
Accumulated deferred income taxes, net
$
15

 
$
14

Total assets of discontinued operations
$
15

 
$
14

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

 
$
1

Asset retirement obligations(a)
26

 
28

Total liabilities of discontinued operations
$
27

 
$
29

(a)
Ameren has completed its retirement obligations at the Hutsonville energy center. The remaining ARO liabilities relate to the abandoned Meredosia energy center.
Segment Information (Tables)
Schedule Of Segment Reporting Information By Segment
The following table presents information about the reported revenues and net income attributable to Ameren common shareholders from continuing operations for the three and nine months ended September 30, 2016 and 2015, and total assets of continuing operations as of September 30, 2016, and December 31, 2015:
Three Months
Ameren
Missouri
 
Ameren
Illinois
 
Other
 
Intersegment
Eliminations
 
Ameren
 
2016
 
 
 
 
 
 
 
 
 
 
External revenues
$
1,150

 
$
675

 
$
34

  
$
—

 
$
1,859

 
Intersegment revenues
15

 
1

 
1

  
(17
)
 
—

 
Net income attributable to Ameren common shareholders from continuing operations
241

 
119

 
9

 
—

 
369

 
2015
 
 
 
 
 
 
 
 
 
 
External revenues
$
1,160

 
$
654

 
$
19

 
$
—

 
$
1,833

 
Intersegment revenues
11

 
1

 
1

 
(13
)
 
—

 
Net income attributable to Ameren common shareholders from continuing operations
239

 
98

 
6

 
—

 
343

 
Nine Months
  
 
  
 
  
 
  
 
  
 
2016
 
 
 
 
 
 
 
 
 
 
External revenues
$
2,733

 
$
1,892

 
$
95

 
$
—

 
$
4,720

 
Intersegment revenues
40

 
3

 
2

 
(45
)
 
—

 
Net income attributable to Ameren common shareholders from continuing operations
347

 
223

 
51

 
—

 
621

 
2015
 
 
 
 
 
 
 
 
 
 
External revenues
$
2,825

 
$
1,910

 
$
55

 
$
—

 
$
4,790

 
Intersegment revenues
30

 
3

 
2

 
(35
)
 
—

 
Net income attributable to Ameren common shareholders from continuing operations
341

 
182

 
26

 
—

 
549

 
As of September 30, 2016:
 
 
 
 
 
 
 
 
 
 
Total assets
$
13,889

 
$
9,202

 
$
1,496

 
$
(468
)
 
$
24,119

(a) 
As of December 31, 2015:
 
 
 
 
 
 
 
 
 
 
Total assets
$
13,851

 
$
8,903

 
$
1,139

 
$
(267
)
 
$
23,626

(a) 
(a)    Excludes total assets from discontinued operations of $15 million and $14 million as of September 30, 2016, and December 31, 2015, respectively.
Summary Of Significant Accounting Policies (Narrative) (Detail) (USD $)
In Millions, except Per Share data, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Basis Of Presentation And Significant Accounting Policies [Line Items]
 
 
 
 
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements
0.3 
1.3 
0.4 
1.2 
Income Tax Expense (Benefit)
 
 
$ 21 
 
Adjustments related to Income Tax Benefit from Share-Based payment per diluted share
 
 
$ 0.09 
 
Excess Tax Benefit from Share-based Compensation, Operating Activities
 
 
 
2 
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense
 
 
$ 32 
$ 12 
Summary Of Significant Accounting Policies (Schedule Of Excise Taxes) (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Accounting Policies [Line Items]
 
 
 
 
Excise tax expense
$ 61 
$ 61 
$ 162 
$ 169 
Union Electric Company
 
 
 
 
Accounting Policies [Line Items]
 
 
 
 
Excise tax expense
52 
52 
122 
127 
Ameren Illinois Company
 
 
 
 
Accounting Policies [Line Items]
 
 
 
 
Excise tax expense
$ 9 
$ 9 
$ 40 
$ 42 
Rate And Regulatory Matters (Narrative-Missouri) (Detail) (USD $)
3 Months Ended 9 Months Ended 3 Months Ended 9 Months Ended 3 Months Ended 9 Months Ended 12 Months Ended 3 Months Ended 9 Months Ended 3 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Union Electric Company
Sep. 30, 2015
Union Electric Company
Sep. 30, 2016
Union Electric Company
Sep. 30, 2015
Union Electric Company
Sep. 30, 2016
Union Electric Company
MEEIA
Sep. 30, 2016
Electric Distribution
Union Electric Company
MEEIA
Sep. 30, 2016
Mark Twain Project
Ameren Transmission Company of Illinois
mi
Dec. 31, 2015
Noranda [Member]
Union Electric Company
Sep. 30, 2016
Noranda [Member]
Electric Distribution
Union Electric Company
Sep. 30, 2016
Components of Rate Increase - Return on Rate Base [Member]
Electric Distribution
Union Electric Company
Sep. 30, 2016
Pending Rate Case
Electric Distribution
Union Electric Company
Sep. 30, 2016
Components of Rate Increase [Member]
Electric Distribution
Union Electric Company
Sep. 30, 2016
Components of Rate Increase - Depreciation Expense [Member]
Electric Distribution
Union Electric Company
Sep. 30, 2016
Components of Rate Increase - Property Taxes [Member]
Electric Distribution
Union Electric Company
Sep. 30, 2016
Components of Rate Increase - Customer Sales Volumes [Member]
Electric Distribution
Union Electric Company
Sep. 30, 2016
Components of Rate Increase - Transmission Charges [Member]
Electric Distribution
Union Electric Company
Sep. 30, 2016
Components of Rate Increase - Pension and Other Post-Employment Benefit Plan Expenses [Member]
Electric Distribution
Union Electric Company
Sep. 30, 2016
Components of Rate Increase - Solar Rebate Expenses [Member]
Electric Distribution
Union Electric Company
Sep. 30, 2016
Components of Rate Increase - Net Energy Costs [Member]
Electric Distribution
Union Electric Company
Sep. 30, 2016
Components of Rate Increase - Income Taxes [Member]
Electric Distribution
Union Electric Company
Sep. 30, 2016
Final Rate Order [Member]
Electric Distribution
Union Electric Company
MEEIA
Dec. 31, 2016
Subsequent Event
Final Rate Order [Member]
Electric Distribution
Union Electric Company
MEEIA
Rate And Regulatory Matters [Line Items]
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Public Utilities, Requested Rate Increase (Decrease), Amount
 
 
 
 
 
 
 
 
 
 
 
 
 
$ 25,000,000 
$ 206,000,000 
$ 74,000,000 
$ 39,000,000 
$ 10,000,000 
$ 51,000,000 
$ 34,000,000 
$ 24,000,000 
$ 15,000,000 
$ 23,000,000 
$ 15,000,000 
 
 
Public Utilities, Requested Return on Equity, Percentage
 
 
 
 
 
 
 
 
 
 
 
 
 
 
9.90% 
 
 
 
 
 
 
 
 
 
 
 
Public Utilities, Requested Equity Capital Structure, Percentage
 
 
 
 
 
 
 
 
 
 
 
 
 
 
51.80% 
 
 
 
 
 
 
 
 
 
 
 
Rate Base
 
 
 
 
 
 
 
 
 
 
 
 
 
 
7,200,000,000 
 
 
 
 
 
 
 
 
 
 
 
Plant Additions to Rate Base
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1,400,000,000 
 
 
 
 
 
 
 
 
 
 
 
Regulatory Asset, Amortization Period
 
 
 
 
 
 
 
 
 
 
 
 
10 years 
 
 
 
 
 
 
 
 
 
 
 
 
 
Revenue Requirement
 
 
 
 
 
 
 
 
 
 
 
78,000,000 
81,000,000 
 
 
 
 
 
 
 
 
 
 
 
 
 
Number of Months to complete MoPSC Electric Service Proceeding
 
 
 
 
 
 
 
 
 
 
 
 
 
 
11 months 
 
 
 
 
 
 
 
 
 
 
 
Incentive Award if Energy Efficiency Goals Are Achieved
 
 
 
 
 
 
 
 
 
19,000,000 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
29,000,000 
28,000,000 
Achieved Percentage of Energy Efficiency Earnings For Incentive Award
 
 
 
 
 
 
 
 
 
100.00% 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Electric
$ 1,725,000,000 
$ 1,700,000,000 
$ 4,101,000,000 
$ 4,093,000,000 
$ 1,144,000,000 
$ 1,151,000,000 
$ 2,682,000,000 
$ 2,752,000,000 
$ 19,000,000 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
$ 9,000,000 
Incentive Award if Energy Efficiency Goals Are Achieved, Period of Recognition
 
 
 
 
 
 
 
 
 
3 years 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Transmission Line Miles
 
 
 
 
 
 
 
 
 
 
95 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Rate And Regulatory Matters (Narrative-Illinois) (Detail) (USD $)
In Millions, unless otherwise specified
1 Months Ended 3 Months Ended
Sep. 30, 2016
Dec. 31, 2015
Sep. 30, 2016
Ameren Illinois Company
Dec. 31, 2015
Ameren Illinois Company
Sep. 30, 2016
2016 IEIMA Revenue Requirement Reconciliation
IEIMA
Ameren Illinois Company
Electric Distribution
Sep. 30, 2016
2015 IEIMA Revenue Requirement Reconciliation
IEIMA
Ameren Illinois Company
Electric Distribution
Sep. 30, 2016
2014 IEIMA Revenue Requirement Reconciliation
IEIMA
Ameren Illinois Company
Electric Distribution
Dec. 31, 2015
2014 IEIMA Revenue Requirement Reconciliation
IEIMA
Ameren Illinois Company
Electric Distribution
Apr. 30, 2016
Pending Rate Case
IEIMA
Ameren Illinois Company
Electric Distribution
Dec. 31, 2016
Subsequent Event
Administrative Law Judge
IEIMA
Ameren Illinois Company
Electric Distribution
Rate And Regulatory Matters [Line Items]
 
 
 
 
 
 
 
 
 
 
Regulatory assets
$ 1,312 
$ 1,382 
$ 791 
$ 771 
$ 23 
$ 66 
 
 
 
 
Current regulatory assets
107 
260 
59 
167 
 
 
22 
103 
 
 
Public Utilities, Requested Rate Increase (Decrease), Amount
 
 
 
 
 
 
 
 
$ 14 
$ 14 
Rate And Regulatory Matters (Narrative-Federal) (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended 9 Months Ended 3 Months Ended 9 Months Ended 9 Months Ended 1 Months Ended 9 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Dec. 31, 2015
Sep. 30, 2015
New Nuclear Energy Center COL [Member]
Sep. 30, 2016
Ameren Illinois Company
Dec. 31, 2015
Ameren Illinois Company
Sep. 30, 2016
Union Electric Company
Sep. 30, 2015
Union Electric Company
Sep. 30, 2016
Union Electric Company
Sep. 30, 2015
Union Electric Company
Dec. 31, 2015
Union Electric Company
Sep. 30, 2015
Union Electric Company
New Nuclear Energy Center COL [Member]
Sep. 30, 2016
Midwest Independent Transmission System Operator, Inc
Final Rate Order [Member]
Sep. 30, 2016
Midwest Independent Transmission System Operator, Inc
Administrative Law Judge
Feb. 28, 2015
Midwest Independent Transmission System Operator, Inc
Pending Ferc Case
Sep. 30, 2016
Midwest Independent Transmission System Operator, Inc
Pending Ferc Case
Sep. 30, 2016
Midwest Independent Transmission System Operator, Inc
Pending Ferc Case
Ameren Illinois Company
Sep. 30, 2016
Maximum
Midwest Independent Transmission System Operator, Inc
Final Rate Order [Member]
Rate And Regulatory Matters [Line Items]
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Public Utilities, Approved Return on Equity, Percentage
 
 
 
 
 
 
 
 
 
 
 
 
 
 
10.32% 
9.70% 
 
12.38% 
 
10.82% 
Customer Requested Rate on Equity
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
8.67% 
9.15% 
 
 
Incentive adder to FERC allowed base return on common equity
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
0.50% 
 
 
Current regulatory liabilities
$ 87 
 
$ 87 
 
$ 80 
 
$ 56 
$ 39 
$ 11 
 
$ 11 
 
$ 28 
 
 
 
 
$ 61 
$ 42 
 
Investments in Power and Distribution Projects
 
 
 
 
 
 
 
 
 
 
 
 
 
69 
 
 
 
 
 
 
Provision for Callaway construction and operating license
$ 0 
$ 0 
$ 0 
$ 69 
 
$ 69 
 
 
$ 0 
$ 0 
$ 0 
$ 69 
 
$ 69 
 
 
 
 
 
 
Short-Term Debt And Liquidity (Narrative) (Detail) (USD $)
3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Utilities
 
 
 
 
Line of Credit Facility [Line Items]
 
 
 
 
Short Term Debt, Weighted Average Interest Rate During Period
0.53% 
0.10% 
0.54% 
0.09% 
Credit Agreements 2012
 
 
 
 
Line of Credit Facility [Line Items]
 
 
 
 
Line of credit facility, maximum borrowing capacity
$ 1,500,000,000 
 
$ 1,500,000,000 
 
Actual debt-to-capital ratio
0.51 
 
0.51 
 
Line of Credit Facility, Covenant Terms, Default Provision, Maximum Indebtedness
$ 75,000,000 
 
$ 75,000,000 
 
Credit Agreements 2012 |
Maximum
 
 
 
 
Line of Credit Facility [Line Items]
 
 
 
 
Actual debt-to-capital ratio
0.65 
 
0.65 
 
Interest Coverage Requirement
200.00% 
 
200.00% 
 
Credit Agreements 2012 |
Union Electric Company |
Maximum
 
 
 
 
Line of Credit Facility [Line Items]
 
 
 
 
Actual debt-to-capital ratio
0.65 
 
0.65 
 
Credit Agreements 2012 |
Ameren Illinois Company |
Maximum
 
 
 
 
Line of Credit Facility [Line Items]
 
 
 
 
Actual debt-to-capital ratio
0.65 
 
0.65 
 
Missouri Credit Agreement 2012 |
Union Electric Company
 
 
 
 
Line of Credit Facility [Line Items]
 
 
 
 
Actual debt-to-capital ratio
0.48 
 
0.48 
 
Illinois Credit Agreement 2012 |
Ameren Illinois Company
 
 
 
 
Line of Credit Facility [Line Items]
 
 
 
 
Actual debt-to-capital ratio
0.46 
 
0.46 
 
Short-Term Debt And Liquidity Short-Term Debt and Liquidity (Commercial Paper outstanding) (Details) (USD $)
In Millions, unless otherwise specified
Sep. 30, 2016
Dec. 31, 2015
Line of Credit Facility [Line Items]
 
 
Commercial paper outstanding
$ 608 
$ 301 
Ameren (parent)
 
 
Line of Credit Facility [Line Items]
 
 
Commercial paper outstanding
451 
301 
Union Electric Company
 
 
Line of Credit Facility [Line Items]
 
 
Commercial paper outstanding
0 
0 
Ameren Illinois Company
 
 
Line of Credit Facility [Line Items]
 
 
Commercial paper outstanding
$ 157 
$ 0 
Short-Term Debt And Liquidity Short-Term Debt and Liquidity (Commercial Paper) (Details) (USD $)
In Millions, unless otherwise specified
9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Line of Credit Facility [Line Items]
 
 
Average Daily Commercial Paper Borrowings Outstanding
$ 563 
$ 832 
Weighted Average Interest Rate
0.793% 
0.56% 
Peak Short Term Borrowings
839 1
1,108 1
Peak Short Term Borrowings Interest Rate
0.95% 
0.70% 
Ameren (parent)
 
 
Line of Credit Facility [Line Items]
 
 
Average Daily Commercial Paper Borrowings Outstanding
435 
770 
Weighted Average Interest Rate
0.811% 
0.56% 
Peak Short Term Borrowings
574 1
874 1
Peak Short Term Borrowings Interest Rate
0.95% 
0.70% 
Union Electric Company
 
 
Line of Credit Facility [Line Items]
 
 
Average Daily Commercial Paper Borrowings Outstanding
80 
56 
Weighted Average Interest Rate
0.739% 
0.50% 
Peak Short Term Borrowings
208 1
294 1
Peak Short Term Borrowings Interest Rate
0.85% 
0.60% 
Ameren Illinois Company
 
 
Line of Credit Facility [Line Items]
 
 
Average Daily Commercial Paper Borrowings Outstanding
48 
6 
Weighted Average Interest Rate
0.722% 
0.44% 
Peak Short Term Borrowings
$ 195 1
$ 48 1
Peak Short Term Borrowings Interest Rate
0.85% 
0.60% 
Long-Term Debt And Equity Financings (Narrative) (Detail) (USD $)
9 Months Ended
Sep. 30, 2016
Long-Term Debt And Equity Financings [Line Items]
 
Debt Default Provision Excess
$ 25,000,000 
Ameren Missouri And Ameren Illinois
 
Long-Term Debt And Equity Financings [Line Items]
 
Assumed interest rate
5.00% 
Dividend rate
6.00% 
Secured Debt |
Senior Secured Notes540 Due2016 [Member] |
Union Electric Company
 
Long-Term Debt And Equity Financings [Line Items]
 
Debt Instrument, Interest Rate, Stated Percentage
5.40% 
Repayments of Other Long-term Debt
260,000,000 
Secured Debt |
Senior Secured Notes, 3.65%, Due 2045 [Member] |
Union Electric Company
 
Long-Term Debt And Equity Financings [Line Items]
 
Debt Instrument, Face Amount
150,000,000 
Debt Instrument, Interest Rate, Stated Percentage
3.65% 
Proceeds from Issuance of Secured Debt
148,000,000 
Secured Debt |
Senior Secured Notes620 Due2016 [Member] |
Ameren Illinois Company
 
Long-Term Debt And Equity Financings [Line Items]
 
Debt Instrument, Interest Rate, Stated Percentage
6.20% 
Repayments of Other Long-term Debt
54,000,000 
Secured Debt |
Senior Secured Notes625 Due2016 [Member] |
Ameren Illinois Company
 
Long-Term Debt And Equity Financings [Line Items]
 
Debt Instrument, Interest Rate, Stated Percentage
6.25% 
Repayments of Other Long-term Debt
$ 75,000,000 
Federal Energy Regulatory Commission Restriction [Member] |
Ameren Illinois Company
 
Long-Term Debt And Equity Financings [Line Items]
 
Common stock equity to total capitalization
51.00% 
Federal Energy Regulatory Commission Restriction [Member] |
Ameren Illinois Company |
Minimum
 
Long-Term Debt And Equity Financings [Line Items]
 
Common stock equity to total capitalization
30.00% 
Long-Term Debt And Equity Financings (Schedule Of Covered Ratio) (Detail) (USD $)
In Millions, unless otherwise specified
9 Months Ended
Sep. 30, 2016
Union Electric Company
 
Long-Term Debt And Equity Financings [Line Items]
 
Bonds Issuable
$ 3,838 1
Preferred Stock Issuable
2,357 
Retired bond capacity
1,206 
Ameren Illinois Company
 
Long-Term Debt And Equity Financings [Line Items]
 
Bonds Issuable
3,942 1 2
Preferred Stock Issuable
203 3
Retired bond capacity
$ 279 
Minimum Required Ratio [Member] |
Minimum |
Union Electric Company
 
Long-Term Debt And Equity Financings [Line Items]
 
Restricted payment interest coverage ratio, Actual
2.0 4
Dividend Coverage Ratio
2.5 5
Minimum Required Ratio [Member] |
Minimum |
Ameren Illinois Company
 
Long-Term Debt And Equity Financings [Line Items]
 
Restricted payment interest coverage ratio, Actual
2.0 4
Dividend Coverage Ratio
1.5 5
Actual Ratio [Member] |
Union Electric Company
 
Long-Term Debt And Equity Financings [Line Items]
 
Restricted payment interest coverage ratio, Actual
4.7 
Dividend Coverage Ratio
105.9 
Actual Ratio [Member] |
Ameren Illinois Company
 
Long-Term Debt And Equity Financings [Line Items]
 
Restricted payment interest coverage ratio, Actual
7.3 
Dividend Coverage Ratio
3.0 
Other Income and Expenses (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Other Nonoperating Income (Expense) [Line Items]
 
 
 
 
Allowance for equity funds used during construction
$ 7 1
$ 8 1
$ 20 1
$ 19 1
Interest income on industrial development revenue bonds
7 1
7 1
20 1
20 1
Interest income
3 1
4 1
11 1
12 1
Other
1 1
0 1
3 1
3 1
Total miscellaneous income
18 1
19 1
54 1
54 1
Donations
1 1
0 1
8 1
10 1
Other
7 1
5 1
13 1
12 1
Total miscellaneous expense
8 1
5 1
21 1
22 1
Union Electric Company
 
 
 
 
Other Nonoperating Income (Expense) [Line Items]
 
 
 
 
Allowance for equity funds used during construction
6 
7 
16 
16 
Interest income on industrial development revenue bonds
7 
7 
20 
20 
Interest income
1 
0 
1 
1 
Other
0 
0 
1 
0 
Total miscellaneous income
14 
14 
38 
37 
Donations
0 
 
2 
3 
Other
2 
3 
4 
5 
Total miscellaneous expense
2 
3 
6 
8 
Ameren Illinois Company
 
 
 
 
Other Nonoperating Income (Expense) [Line Items]
 
 
 
 
Allowance for equity funds used during construction
1 
1 
4 
3 
Interest income
2 
3 
9 
10 
Other
1 
0 
2 
2 
Total miscellaneous income
4 
4 
15 
15 
Donations
1 
0 
6 
4 
Other
2 
3 
5 
6 
Total miscellaneous expense
$ 3 
$ 3 
$ 11 
$ 10 
Derivative Financial Instruments (Open Gross Derivative Volumes By Commodity Type) (Detail)
Sep. 30, 2016
gal
Dec. 31, 2015
gal
Fuel Oils
 
 
Derivative [Line Items]
 
 
Quantity
25,000,000 1
35,000,000 1
Natural Gas
 
 
Derivative [Line Items]
 
 
Quantity
154,000,000 
181,000,000 
Power
 
 
Derivative [Line Items]
 
 
Quantity
10,000,000 
11,000,000 
Uranium
 
 
Derivative [Line Items]
 
 
Quantity
445,000 
494,000 
Union Electric Company |
Fuel Oils
 
 
Derivative [Line Items]
 
 
Quantity
25,000,000 1
35,000,000 1
Union Electric Company |
Natural Gas
 
 
Derivative [Line Items]
 
 
Quantity
26,000,000 
30,000,000 
Union Electric Company |
Power
 
 
Derivative [Line Items]
 
 
Quantity
1,000,000 
1,000,000 
Union Electric Company |
Uranium
 
 
Derivative [Line Items]
 
 
Quantity
445,000 
494,000 
Ameren Illinois Company |
Natural Gas
 
 
Derivative [Line Items]
 
 
Quantity
128,000,000 
151,000,000 
Ameren Illinois Company |
Power
 
 
Derivative [Line Items]
 
 
Quantity
9,000,000 
10,000,000 
Derivative Financial Instruments (Derivative Instruments Carrying Value) (Detail) (Not Designated As Hedging Instrument, USD $)
In Millions, unless otherwise specified
Sep. 30, 2016
Dec. 31, 2015
Derivative [Line Items]
 
 
Derivative assets
$ 15 1
$ 18 1
Derivative liabilities
215 2
264 2
Fuel Oils |
Other Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
1 
 
Fuel Oils |
Other Current Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
8 
22 
Fuel Oils |
Other Deferred Credits And Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
1 
7 
Natural Gas |
Other Current Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
2 
1 
Natural Gas |
Other Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
1 
1 
Natural Gas |
Other Current Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
12 
38 
Natural Gas |
Other Deferred Credits And Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
15 
26 
Power |
Other Current Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
11 
16 
Power |
Other Current Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
14 
13 
Power |
Other Deferred Credits And Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
160 
157 
Uranium |
Other Current Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
2 
1 
Uranium |
Other Deferred Credits And Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
3 
 
Union Electric Company
 
 
Derivative [Line Items]
 
 
Derivative assets
12 1
17 1
Derivative liabilities
25 2
44 2
Union Electric Company |
Fuel Oils |
Other Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
1 
 
Union Electric Company |
Fuel Oils |
Other Current Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
8 
22 
Union Electric Company |
Fuel Oils |
Other Deferred Credits And Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
1 
7 
Union Electric Company |
Natural Gas |
Other Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
0 
1 
Union Electric Company |
Natural Gas |
Other Current Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
3 
6 
Union Electric Company |
Natural Gas |
Other Deferred Credits And Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
6 
8 
Union Electric Company |
Power |
Other Current Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
11 
16 
Union Electric Company |
Power |
Other Current Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
2 
 
Union Electric Company |
Power |
Other Deferred Credits And Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
0 
0 
Union Electric Company |
Uranium |
Other Current Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
2 
1 
Union Electric Company |
Uranium |
Other Deferred Credits And Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
3 
 
Ameren Illinois Company
 
 
Derivative [Line Items]
 
 
Derivative assets
3 1
1 1
Derivative liabilities
190 2
220 2
Ameren Illinois Company |
Fuel Oils |
Other Current Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
0 
0 
Ameren Illinois Company |
Fuel Oils |
Other Deferred Credits And Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
0 
0 
Ameren Illinois Company |
Natural Gas |
Other Current Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
2 
1 
Ameren Illinois Company |
Natural Gas |
Other Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
1 
 
Ameren Illinois Company |
Natural Gas |
Other Current Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
0 
0 
Ameren Illinois Company |
Natural Gas |
Other Deferred Credits And Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
9 
18 
Ameren Illinois Company |
Natural Gas |
Mark To Market Derivative Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
9 
32 
Ameren Illinois Company |
Power |
Other Current Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
0 
0 
Ameren Illinois Company |
Power |
Other Current Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
0 
0 
Ameren Illinois Company |
Power |
Other Deferred Credits And Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
160 
157 
Ameren Illinois Company |
Power |
Mark To Market Derivative Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
12 
13 
Ameren Illinois Company |
Uranium |
Other Current Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
0 
0 
Ameren Illinois Company |
Uranium |
Other Deferred Credits And Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
$ 0 
 
Derivative Financial Instruments (Offsetting Derivative Assets and Liabilities) (Details) (Commodity Contract, USD $)
In Millions, unless otherwise specified
Sep. 30, 2016
Dec. 31, 2015
Offsetting Assets and Liabilities [Line Items]
 
 
Gross Amounts Recognized in the Balance Sheet
$ 15 1
$ 18 1
Derivative Instruments
4 
1 
Derivative, Collateral, Obligation to Return Cash
0 2
0 2
Net Amount
11 
17 
Gross Amounts Recognized in the Balance Sheet
215 1
264 1
Derivative Instruments
4 
1 
Cash Collateral Received/Posted
5 2
11 2
Net Amount
206 
252 
Union Electric Company
 
 
Offsetting Assets and Liabilities [Line Items]
 
 
Gross Amounts Recognized in the Balance Sheet
12 1
17 1
Derivative Instruments
2 
1 
Derivative, Collateral, Obligation to Return Cash
0 2
0 2
Net Amount
10 
16 
Gross Amounts Recognized in the Balance Sheet
25 1
44 1
Derivative Instruments
2 
1 
Cash Collateral Received/Posted
5 2
8 2
Net Amount
18 
35 
Ameren Illinois Company
 
 
Offsetting Assets and Liabilities [Line Items]
 
 
Gross Amounts Recognized in the Balance Sheet
3 
1 
Derivative Instruments
2 
0 
Derivative, Collateral, Obligation to Return Cash
0 2
0 2
Net Amount
1 
1 
Gross Amounts Recognized in the Balance Sheet
190 1
220 1
Derivative Instruments
2 
0 
Cash Collateral Received/Posted
0 2
3 2
Net Amount
$ 188 
$ 217 
Fair Value Measurements (Schedule Of Valuation Process And Unobservable Inputs) (Detail) (USD $)
In Millions, unless otherwise specified
9 Months Ended 12 Months Ended
Sep. 30, 2016
Dec. 31, 2015
Natural Gas |
Discounted Cash Flow |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
 
0.40% 1 2
Nodal basis
 
(0.10)3
Credit risk
 
0.40% 1 2
Natural Gas |
Discounted Cash Flow |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
 
12.00% 1 2
Nodal basis
 
0 3
Credit risk
 
0.40% 1 2
Natural Gas |
Discounted Cash Flow |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
 
7.00% 1 2
Nodal basis
 
(0.10)3
Credit risk
 
0.40% 1 2
Natural Gas |
Option Model |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
 
35.00% 3
Nodal basis
 
(0.30)2
Natural Gas |
Option Model |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
 
55.00% 3
Nodal basis
 
0 2
Natural Gas |
Option Model |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
 
45.00% 3
Nodal basis
 
(0.20)2
Natural Gas |
Derivative Assets
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative assets
 
$ 1 4
Natural Gas |
Derivative Liabilities
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative liabilities
 
(1)4
Fuel Oils |
Discounted Cash Flow |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
0.22% 1 2
 
Credit risk
0.38% 2 3
 
Fuel Oils |
Discounted Cash Flow |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
0.22% 1 2
 
Credit risk
0.38% 2 3
 
Fuel Oils |
Discounted Cash Flow |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
0.22% 1 2
 
Credit risk
0.38% 2 3
 
Fuel Oils |
Option Model |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
25.00% 5
 
Fuel Oils |
Option Model |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
38.00% 3
 
Fuel Oils |
Option Model |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
26.00% 3
 
Fuel Oils |
Derivative Assets
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative assets
1 4
 
Fuel Oils |
Derivative Liabilities
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative liabilities
0 4
 
Power |
Discounted Cash Flow |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
0.56% 1 2
0.86% 1 2
Nodal basis
(6)6
(10)6
Credit risk
0.38% 1 2
0.40% 1 2
Average forward peak and off-peak pricing
25 6
22 6
Estimated auction price
(253)3
(270)3
Power |
Discounted Cash Flow |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
0.56% 1 2
0.86% 1 2
Nodal basis
0 6
(1)6
Credit risk
0.38% 1 2
0.40% 1 2
Average forward peak and off-peak pricing
42 6
39 6
Estimated auction price
3,593 3
2,057 3
Power |
Discounted Cash Flow |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
0.56% 1 2
0.86% 1 2
Nodal basis
(2)6
(3)6
Credit risk
0.38% 1 2
0.40% 1 2
Average forward peak and off-peak pricing
29 6
29 6
Estimated auction price
31 3
211 3
Power |
Fundamental Energy Production Model |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Escalation rate
4.00% 3 7
3.00% 3 7
Estimated future gas prices
3 3
3 3
Power |
Fundamental Energy Production Model |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Escalation rate
4.00% 3 7
3.00% 3 7
Estimated future gas prices
5 3
4 3
Power |
Fundamental Energy Production Model |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Escalation rate
4.00% 3 7
3.00% 3 7
Estimated future gas prices
4 3
4 3
Power |
Contract Price Allocation |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Estimated renewable energy credit costs
5 3
5 3
Power |
Contract Price Allocation |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Estimated renewable energy credit costs
7 3
7 3
Power |
Contract Price Allocation |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Estimated renewable energy credit costs
6 3
6 3
Power |
Derivative Assets
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative assets
11 4 8
16 4 8
Power |
Derivative Liabilities
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative liabilities
(174)4 8
(170)4 8
Uranium |
Discounted Cash Flow |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Credit risk
0.38% 1 2
0.40% 1 2
Average forward pricing
22 3
35 3
Uranium |
Discounted Cash Flow |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Credit risk
0.38% 1 2
0.40% 1 2
Average forward pricing
26 3
42 3
Uranium |
Discounted Cash Flow |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Credit risk
0.38% 1 2
0.40% 1 2
Average forward pricing
24 3
37 3
Uranium |
Option Model |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
20.00% 3
20.00% 3
Uranium |
Option Model |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
20.00% 3
20.00% 3
Uranium |
Option Model |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
20.00% 3
20.00% 3
Uranium |
Derivative Assets
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative assets
0 4
0 4
Uranium |
Derivative Liabilities
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative liabilities
$ (5)4
$ (1)4
Fair Value Measurements (Schedule Of Fair Value Hierarchy Of Assets And Liabilities Measured At Fair Value On Recurring Basis) (Detail) (USD $)
In Millions, unless otherwise specified
Sep. 30, 2016
Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
$ 597 1
$ 557 2
Assets fair value
612 3
575 3
Excluded receivables, payables, and accrued income, net
2 
(1)
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
597 1
557 2
Assets fair value
609 3
574 3
Excluded receivables, payables, and accrued income, net
2 
(1)
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
15 3
18 3
Derivative liabilities
215 3
264 3
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
12 3
17 3
Derivative liabilities
25 3
44 3
Commodity Contract |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
3 
1 
Derivative liabilities
190 3
220 3
Cash and cash equivalents
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
3 
4 
Cash and cash equivalents |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
3 
4 
Equity Securities |
U.S. large capitalization
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
393 
364 
Equity Securities |
U.S. large capitalization |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
393 
364 
Debt Securities |
Corporate bonds
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
64 
58 
Debt Securities |
Corporate bonds |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
64 
58 
Debt Securities |
US treasury and government securities
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
120 
109 
Debt Securities |
US treasury and government securities |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
120 
109 
Debt Securities |
Other Debt Securities
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
17 
22 
Debt Securities |
Other Debt Securities |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
17 
22 
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
396 
368 
Assets fair value
396 3
368 3
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
396 
368 
Assets fair value
396 3
368 3
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 3
0 3
Derivative liabilities
9 3
30 3
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 3
0 3
Derivative liabilities
9 3
29 3
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
0 3
1 
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Cash and cash equivalents
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
3 
4 
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Cash and cash equivalents |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
3 
4 
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Equity Securities |
U.S. large capitalization
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
393 
364 
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Equity Securities |
U.S. large capitalization |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
393 
364 
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Debt Securities |
Corporate bonds
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Debt Securities |
Corporate bonds |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Debt Securities |
US treasury and government securities
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Debt Securities |
US treasury and government securities |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Debt Securities |
Other Debt Securities
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Debt Securities |
Other Debt Securities |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Significant Other Observable Inputs (Level 2)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
201 
189 
Assets fair value
204 3
190 3
Significant Other Observable Inputs (Level 2) |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
201 
189 
Assets fair value
201 3
189 3
Significant Other Observable Inputs (Level 2) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
3 3
1 3
Derivative liabilities
27 3
62 3
Significant Other Observable Inputs (Level 2) |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 3
0 3
Derivative liabilities
9 3
13 3
Significant Other Observable Inputs (Level 2) |
Commodity Contract |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
18 3
49 3
Significant Other Observable Inputs (Level 2) |
Cash and cash equivalents
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Significant Other Observable Inputs (Level 2) |
Cash and cash equivalents |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Significant Other Observable Inputs (Level 2) |
Equity Securities |
U.S. large capitalization
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Significant Other Observable Inputs (Level 2) |
Equity Securities |
U.S. large capitalization |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Significant Other Observable Inputs (Level 2) |
Debt Securities |
Corporate bonds
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
64 
58 
Significant Other Observable Inputs (Level 2) |
Debt Securities |
Corporate bonds |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
64 
58 
Significant Other Observable Inputs (Level 2) |
Debt Securities |
US treasury and government securities
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
120 
109 
Significant Other Observable Inputs (Level 2) |
Debt Securities |
US treasury and government securities |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
120 
109 
Significant Other Observable Inputs (Level 2) |
Debt Securities |
Other Debt Securities
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
17 
22 
Significant Other Observable Inputs (Level 2) |
Debt Securities |
Other Debt Securities |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
17 
22 
Significant Other Unobservable Inputs (Level 3)
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Assets fair value
12 3
17 3
Significant Other Unobservable Inputs (Level 3) |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Assets fair value
12 3
17 3
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
12 3
17 3
Derivative liabilities
179 3
172 3
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
12 3
17 3
Derivative liabilities
7 3
2 3
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
172 3
170 3
Significant Other Unobservable Inputs (Level 3) |
Cash and cash equivalents
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Significant Other Unobservable Inputs (Level 3) |
Cash and cash equivalents |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Significant Other Unobservable Inputs (Level 3) |
Equity Securities |
U.S. large capitalization
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Significant Other Unobservable Inputs (Level 3) |
Equity Securities |
U.S. large capitalization |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Significant Other Unobservable Inputs (Level 3) |
Debt Securities |
Corporate bonds
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Significant Other Unobservable Inputs (Level 3) |
Debt Securities |
Corporate bonds |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Significant Other Unobservable Inputs (Level 3) |
Debt Securities |
US treasury and government securities
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Significant Other Unobservable Inputs (Level 3) |
Debt Securities |
US treasury and government securities |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Significant Other Unobservable Inputs (Level 3) |
Debt Securities |
Other Debt Securities
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Significant Other Unobservable Inputs (Level 3) |
Debt Securities |
Other Debt Securities |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Uranium |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
5 3
1 3
Uranium |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
5 3
1 3
Uranium |
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
0 3
0 3
Uranium |
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
0 3
0 3
Uranium |
Significant Other Observable Inputs (Level 2) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
0 3
0 3
Uranium |
Significant Other Observable Inputs (Level 2) |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
0 3
0 3
Uranium |
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
5 3
1 3
Uranium |
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
5 3
1 3
Fuel Oils |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
1 3
 
Derivative liabilities
9 3
29 3
Fuel Oils |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
1 3
 
Derivative liabilities
9 3
29 3
Fuel Oils |
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 3
 
Derivative liabilities
9 3
29 3
Fuel Oils |
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 3
 
Derivative liabilities
9 3
29 3
Fuel Oils |
Significant Other Observable Inputs (Level 2) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 3
 
Derivative liabilities
0 3
0 3
Fuel Oils |
Significant Other Observable Inputs (Level 2) |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 3
 
Derivative liabilities
0 3
0 3
Fuel Oils |
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
1 3
 
Derivative liabilities
0 3
0 3
Fuel Oils |
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
1 3
 
Derivative liabilities
0 3
0 3
Power |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
11 3
16 3
Derivative liabilities
174 3
170 3
Power |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
11 3
16 3
Derivative liabilities
2 3
 
Power |
Commodity Contract |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
172 3
170 3
Power |
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 3
0 3
Derivative liabilities
0 3
0 3
Power |
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 3
0 3
Derivative liabilities
0 3
 
Power |
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
0 3
0 3
Power |
Significant Other Observable Inputs (Level 2) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 3
0 3
Derivative liabilities
0 3
0 3
Power |
Significant Other Observable Inputs (Level 2) |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 3
0 3
Derivative liabilities
0 3
 
Power |
Significant Other Observable Inputs (Level 2) |
Commodity Contract |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
0 3
0 
Power |
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
11 3
16 3
Derivative liabilities
174 3
170 3
Power |
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
11 3
16 3
Derivative liabilities
2 3
 
Power |
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
172 3
170 3
Natural Gas |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
3 3
2 3
Derivative liabilities
27 3
64 3
Natural Gas |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
 
1 3
Derivative liabilities
9 3
14 3
Natural Gas |
Commodity Contract |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
3 3
1 3
Derivative liabilities
18 3
50 3
Natural Gas |
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 3
0 3
Derivative liabilities
0 3
1 3
Natural Gas |
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
 
0 3
Derivative liabilities
0 3
0 3
Natural Gas |
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 3
0 3
Derivative liabilities
0 3
1 3
Natural Gas |
Significant Other Observable Inputs (Level 2) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
3 3
1 3
Derivative liabilities
27 3
62 3
Natural Gas |
Significant Other Observable Inputs (Level 2) |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
 
0 3
Derivative liabilities
9 3
13 3
Natural Gas |
Significant Other Observable Inputs (Level 2) |
Commodity Contract |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
3 3
1 3
Derivative liabilities
18 3
49 3
Natural Gas |
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 3
1 3
Derivative liabilities
0 3
1 3
Natural Gas |
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
 
1 3
Derivative liabilities
0 3
1 3
Natural Gas |
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 3
0 3
Derivative liabilities
$ 0 3
$ 0 3
Fair Value Measurements (Schedule Of Changes In The Fair Value Of Financial Assets And Liabilities Classified As Level Three In The Fair Value Hierarchy) (Detail) (Power, USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Jun. 30, 2016
Dec. 31, 2015
Jun. 30, 2015
Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
 
 
 
 
 
 
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value
$ (163)
$ (148)
$ (163)
$ (148)
$ (155)
$ (154)
$ (138)
$ (133)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
 
 
 
 
 
 
 
 
Included in regulatory assets/liabilities
(6)
(6)
(17)
(37)
 
 
 
 
Purchases
 
 
13 
29 
 
 
 
 
Settlements
(2)
(4)
(5)
(7)
 
 
 
 
Change in unrealized gains (losses) related to assets/liabilities held at period end
(2)
(6)
(7)
(34)
 
 
 
 
Union Electric Company
 
 
 
 
 
 
 
 
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
 
 
 
 
 
 
 
 
Beginning balance
14 
27 
16 
9 
 
 
 
 
Included in regulatory assets/liabilities
0 
2 
(4)
 
 
 
 
 
Purchases
 
 
13 
29 
 
 
 
 
Settlements
(5)
(7)
(16)
(16)
 
 
 
 
Ending balance
9 
22 
9 
22 
 
 
 
 
Change in unrealized gains (losses) related to assets/liabilities held at period end
0 
1 
0 
1 
 
 
 
 
Ameren Illinois Company
 
 
 
 
 
 
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
 
 
 
 
 
 
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value
(172)
(170)
(172)
(170)
(169)
(170)
(165)
(142)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
 
 
 
 
 
 
 
 
Included in regulatory assets/liabilities
(6)
(8)
(13)
(37)
 
 
 
 
Purchases
 
 
0 
0 
 
 
 
 
Settlements
3 
3 
11 
9 
 
 
 
 
Change in unrealized gains (losses) related to assets/liabilities held at period end
$ (2)
$ (7)
$ (7)
$ (35)
 
 
 
 
Fair Value Measurements (Schedule Of Carrying Amounts And Estimated Fair Values Of Long-Term Debt And Preferred Stock) (Detail) (USD $)
In Millions, unless otherwise specified
Sep. 30, 2016
Dec. 31, 2015
Fair Value
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Long-term debt (including current portion)
$ 7,971 1
$ 7,814 1
Preferred stock
131 1
125 1
Fair Value |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Long-term debt (including current portion)
4,551 
4,449 
Preferred stock
79 
75 
Fair Value |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Long-term debt (including current portion)
2,682 
2,665 
Preferred stock
52 
50 
Carrying Amount
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Long-term debt (including current portion)
7,038 1
7,275 1
Preferred stock
142 1
142 1
Carrying Amount |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Long-term debt (including current portion)
4,000 
4,110 
Preferred stock
80 
80 
Carrying Amount |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Long-term debt (including current portion)
2,344 
2,471 
Preferred stock
$ 62 
$ 62 
Related Party Transactions Narrative (Details) (Ameren Illinois Company, Ameren Illinois Power Supply Agreements with Ameren Missouri)
9 Months Ended
Sep. 30, 2016
MWh
April 2016 Procurement [Member]
 
Related Party Transaction [Line Items]
 
Long-term Contract for Purchase of Electric Power, Related Party Contract, Fixed Power
375,200 
Long-term Contract for Purchase of Electric Power, Related Party Contract, Fixed Power, Rate
34.71 
September 2016 Procurement [Member]
 
Related Party Transaction [Line Items]
 
Long-term Contract for Purchase of Electric Power, Related Party Contract, Fixed Power
82,800 
Long-term Contract for Purchase of Electric Power, Related Party Contract, Fixed Power, Rate
34.35 
Commitments And Contingencies (Callaway Energy Center) (Detail) (USD $)
9 Months Ended
Sep. 30, 2016
Commitments And Contingencies [Line Items]
 
Threshold for which a retrospective assessment for a covered loss is necessary
$ 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 in calendar year per reactor incident under Price Andersen Liability Provisions of Atomic Energy Act
19,000,000 
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 
Inflationary adjustment prescribed by most recent Price-Anderson Act renewal, in years
5 years 
Aggregate nuclear power industry insurance policy limit for losses from terrorist attacks within twelve month period
3,240,000,000 
Public Liability
 
Commitments And Contingencies [Line Items]
 
Maximum Coverages
13,361,000,000 1
Maximum Assessments for Single Incidents
127,000,000 
Public Liability And Nuclear Worker Liability - American Nuclear Insurers
 
Commitments And Contingencies [Line Items]
 
Maximum Coverages
375,000,000 
Maximum Assessments for Single Incidents
0 
Public Liability And Nuclear Worker Liability - Pool Participation
 
Commitments And Contingencies [Line Items]
 
Maximum Coverages
12,986,000,000 2
Maximum Assessments for Single Incidents
127,000,000 3
Property Damage
 
Commitments And Contingencies [Line Items]
 
Maximum Coverages
3,200,000,000 
Maximum Assessments for Single Incidents
30,000,000 
Property Damage - Nuclear Electric Insurance Ltd
 
Commitments And Contingencies [Line Items]
 
Maximum Coverages
2,750,000,000 4
Maximum Assessments for Single Incidents
30,000,000 5
Property Damage European Mutual Association for Nuclear Insurance
 
Commitments And Contingencies [Line Items]
 
Maximum Coverages
450,000,000 6
Replacement Power - Nuclear Electric Insurance Ltd
 
Commitments And Contingencies [Line Items]
 
Maximum Coverages
490,000,000 7
Maximum Assessments for Single Incidents
7,000,000 5
Amount of weekly indemnity coverage thereafter not exceeding policy limit
490,000,000 
Sub-limit of for non-nuclear events
328,000,000 
Non-radiation event
 
Commitments And Contingencies [Line Items]
 
Maximum Coverages
2,300,000,000 
Aggregate nuclear power industry insurance policy limit for losses from terrorist attacks within twelve month period
1,830,000,000 
Radiation Event
 
Commitments And Contingencies [Line Items]
 
Maximum Coverages
$ 2,750,000,000 
Commitments And Contingencies (Other Obligations) (Detail) (USD $)
In Millions, unless otherwise specified
9 Months Ended
Sep. 30, 2016
MWh
Long-term Purchase Commitment [Line Items]
 
Total Other Obligations
$ 4,328 
Union Electric Company
 
Long-term Purchase Commitment [Line Items]
 
Total Other Obligations
2,428 
Ameren Illinois Company
 
Long-term Purchase Commitment [Line Items]
 
Total Other Obligations
1,859 
April 2016 Procurement [Member] |
Ameren Illinois Company
 
Long-term Purchase Commitment [Line Items]
 
Amount of Megawatthours
3,609,800 
Long-term Purchase Commitment, Amount
105 
September 2016 Procurement [Member] |
Ameren Illinois Company
 
Long-term Purchase Commitment [Line Items]
 
Amount of Megawatthours
2,229,800 
Long-term Purchase Commitment, Amount
71 
September 2016 Procurement - Capacity [Member] |
Ameren Illinois Company
 
Long-term Purchase Commitment [Line Items]
 
Long-term Purchase Commitment, Amount
$ 96 
Amount of Megawatts
1,854 
Commitments And Contingencies (Environmental Matters) (Detail) (USD $)
In Millions, unless otherwise specified
Sep. 30, 2016
scrubber
Dec. 31, 2015
Loss Contingencies [Line Items]
 
 
Percentage of Rate Base Related to Carbon Dioxide Energy Centers
 
20.00% 
Minimum
 
 
Loss Contingencies [Line Items]
 
 
Estimated capital costs to comply with existing and known federal and state air emissions regulations
$ 600 
 
Maximum
 
 
Loss Contingencies [Line Items]
 
 
Estimated capital costs to comply with existing and known federal and state air emissions regulations
700 
 
Union Electric Company
 
 
Loss Contingencies [Line Items]
 
 
Percentage of Rate Base Related to Carbon Dioxide Energy Centers
 
35.00% 
Number of Energy Center Scrubbers
2 
 
Manufactured Gas Plant
 
 
Loss Contingencies [Line Items]
 
 
Accrual for environmental loss contingencies
204 
 
Manufactured Gas Plant |
Ameren Illinois Company
 
 
Loss Contingencies [Line Items]
 
 
Number of remediation sites
44 
 
Accrual for environmental loss contingencies
204 
 
Manufactured Gas Plant |
Ameren Illinois Company |
Minimum
 
 
Loss Contingencies [Line Items]
 
 
Estimate of possible loss
204.0 
 
Manufactured Gas Plant |
Ameren Illinois Company |
Maximum
 
 
Loss Contingencies [Line Items]
 
 
Estimate of possible loss
274.0 
 
Sauget Area Two |
Union Electric Company
 
 
Loss Contingencies [Line Items]
 
 
Accrual for environmental loss contingencies
1 
 
Sauget Area Two |
Union Electric Company |
Minimum
 
 
Loss Contingencies [Line Items]
 
 
Estimate of possible loss
1.0 
 
Sauget Area Two |
Union Electric Company |
Maximum
 
 
Loss Contingencies [Line Items]
 
 
Estimate of possible loss
$ 2.5 
 
Callaway Energy Center (Narrative) (Detail) (Nuclear Plant, USD $)
In Millions, unless otherwise specified
9 Months Ended
Sep. 30, 2016
mill
Nuclear Plant
 
Nuclear Waste Matters [Line Items]
 
Number of mills charged for NWF fee
1 
Annual decommissioning costs included in costs of service
$ 7 
Retirement Benefits (Components Of Net Periodic Benefit Cost) (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Pension Plan
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Service cost
$ 20 
$ 23 
$ 60 
$ 69 
Interest cost
46 
43 
138 
130 
Expected return on plan assets
(63)
(62)
(189)
(186)
Prior service cost (benefit)
0 
0 
0 
0 
Actuarial loss
8 
19 
24 
56 
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements
0 
0 
0 
1 
Net periodic benefit cost
11 1 2
23 1 2
33 1 2
70 1 2
Other Postretirement Benefit Plan, Defined Benefit
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Service cost
5 
6 
15 
17 
Interest cost
12 
12 
36 
36 
Expected return on plan assets
(18)
(17)
(54)
(51)
Prior service cost (benefit)
(1)
(1)
(3)
(3)
Actuarial loss
(3)
1 
(8)
4 
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements
0 
0 
0 
0 
Net periodic benefit cost
(5)1 2
1 1 2
(14)1 2
3 1 2
Union Electric Company |
Pension Plan
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Net periodic benefit cost
6 
14 
19 
42 
Union Electric Company |
Other Postretirement Benefit Plan, Defined Benefit
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Net periodic benefit cost
(1)
2 
(3)
6 
Ameren Illinois Company |
Pension Plan
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Net periodic benefit cost
6 
9 
17 
28 
Ameren Illinois Company |
Other Postretirement Benefit Plan, Defined Benefit
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Net periodic benefit cost
(3)
 
(10)
(2)
Other Affiliated Entities and Intercompany Eliminations [Member] |
Pension Plan
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Net periodic benefit cost
(1)
0 
(3)
0 
Other Affiliated Entities and Intercompany Eliminations [Member] |
Other Postretirement Benefit Plan, Defined Benefit
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Net periodic benefit cost
$ (1)
$ (1)
$ (1)
$ (1)
Retirement Benefits (Summary Of Benefit Plan Costs Incurred) (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Pension Plan
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Defined Benefit Plan, Net Periodic Benefit Cost
$ 11 1 2
$ 23 1 2
$ 33 1 2
$ 70 1 2
Pension Plan |
Union Electric Company
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Defined Benefit Plan, Net Periodic Benefit Cost
6 
14 
19 
42 
Pension Plan |
Ameren Illinois Company
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Defined Benefit Plan, Net Periodic Benefit Cost
6 
9 
17 
28 
Pension Plan |
Other Affiliated Entities and Intercompany Eliminations [Member]
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Defined Benefit Plan, Net Periodic Benefit Cost
(1)
0 
(3)
0 
Other Postretirement Benefit Plan, Defined Benefit
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Defined Benefit Plan, Net Periodic Benefit Cost
(5)1 2
1 1 2
(14)1 2
3 1 2
Other Postretirement Benefit Plan, Defined Benefit |
Union Electric Company
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Defined Benefit Plan, Net Periodic Benefit Cost
(1)
2 
(3)
6 
Other Postretirement Benefit Plan, Defined Benefit |
Ameren Illinois Company
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Defined Benefit Plan, Net Periodic Benefit Cost
(3)
 
(10)
(2)
Other Postretirement Benefit Plan, Defined Benefit |
Other Affiliated Entities and Intercompany Eliminations [Member]
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Defined Benefit Plan, Net Periodic Benefit Cost
$ (1)
$ (1)
$ (1)
$ (1)
Divestiture Transactions and Discontinued Operations Divestiture Transactions and Discontinued operations (Components of Discontinued Operations in Consolidated Statement of Income (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Discontinued Operations and Disposal Groups [Abstract]
 
 
 
 
Operating revenues
 
$ 0 
 
$ 0 
Operating benefits (expenses)
 
(1)
 
2 
Operating income (loss) before income tax
 
(1)
 
2 
Income tax benefit
 
1 
 
50 
Income from Discontinued Operations, Net of Taxes
$ 0 
$ 0 
$ 0 
$ 52 
Divestiture Transactions and Discontinued Operations Divestiture Transactions and DIscontinued Operations (Components of Assets and Liabilities on Consolidated Balance Sheet) (Details) (USD $)
In Millions, unless otherwise specified
Sep. 30, 2016
Dec. 31, 2015
Assets of discontinued operations
 
 
Accumulated deferred income taxes, net
$ 15 
$ 14 
Total assets of discontinued operations
15 
14 
Liabilities of discontinued operations
 
 
Accounts payable and other current obligations
1 
1 
Asset retirement obligations
26 1
28 1
Total liabilities of discontinued operations
$ 27 
$ 29 
Segment Information (Schedule Of Segment Reporting Information By Segment) (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
segment
Sep. 30, 2015
Dec. 31, 2015
Segment Reporting Information [Line Items]
 
 
 
 
 
Number of Reportable Segments
 
 
2 
 
 
External revenues
$ 1,859 
$ 1,833 
$ 4,720 
$ 4,790 
 
Net income attributable to Ameren Common Shareholders from continuing operations
369 
343 
621 
549 
 
Total assets
24,134 
 
24,134 
 
23,640 
Assets of discontinued operations
15 
 
15 
 
14 
Other
 
 
 
 
 
Segment Reporting Information [Line Items]
 
 
 
 
 
External revenues
34 
19 
95 
55 
 
Intersegment revenues
1 
1 
2 
2 
 
Net income attributable to Ameren Common Shareholders from continuing operations
9 
6 
51 
26 
 
Total assets
1,496 
 
1,496 
 
1,139 
Consolidated, Continuing Operations
 
 
 
 
 
Segment Reporting Information [Line Items]
 
 
 
 
 
External revenues
1,859 
1,833 
4,720 
4,790 
 
Net income attributable to Ameren Common Shareholders from continuing operations
369 
343 
621 
549 
 
Total assets
24,119 1
 
24,119 1
 
23,626 1
Operating Segments [Member] |
Union Electric Company
 
 
 
 
 
Segment Reporting Information [Line Items]
 
 
 
 
 
Number of Reportable Segments
 
 
1 
 
 
External revenues
1,150 
1,160 
2,733 
2,825 
 
Intersegment revenues
15 
11 
40 
30 
 
Net income attributable to Ameren Common Shareholders from continuing operations
241 
239 
347 
341 
 
Total assets
13,889 
 
13,889 
 
13,851 
Operating Segments [Member] |
Ameren Illinois Company
 
 
 
 
 
Segment Reporting Information [Line Items]
 
 
 
 
 
Number of Reportable Segments
 
 
1 
 
 
External revenues
675 
654 
1,892 
1,910 
 
Intersegment revenues
1 
1 
3 
3 
 
Net income attributable to Ameren Common Shareholders from continuing operations
119 
98 
223 
182 
 
Total assets
9,202 
 
9,202 
 
8,903 
Intersegment Eliminations
 
 
 
 
 
Segment Reporting Information [Line Items]
 
 
 
 
 
Intersegment revenues
(17)
(13)
(45)
(35)
 
Total assets
$ (468)
 
$ (468)
 
$ (267)