AMEREN ILLINOIS CO, 10-Q filed on 8/6/2015
Quarterly Report
Document and Entity Information
6 Months Ended
Jun. 30, 2015
Jul. 31, 2015
Entity Information [Line Items]
 
 
Document Type
10-Q 
 
Amendment Flag
false 
 
Document Period End Date
Jun. 30, 2015 
 
Document Fiscal Year Focus
2015 
 
Document Fiscal Period Focus
Q2 
 
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
Jun. 30, 2015 
 
Document Fiscal Year Focus
2015 
 
Document Fiscal Period Focus
Q2 
 
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
Jun. 30, 2015 
 
Document Fiscal Year Focus
2015 
 
Document Fiscal Period Focus
Q2 
 
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 6 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Jun. 30, 2014
Operating Revenues:
 
 
 
 
Electric
$ 1,250 
$ 1,235 
$ 2,393 
$ 2,341 
Gas
151 
184 
564 
672 
Total operating revenues
1,401 
1,419 
2,957 
3,013 
Operating Expenses:
 
 
 
 
Fuel
205 
198 
411 
402 
Purchased power
101 
112 
240 
226 
Gas purchased for resale
46 
79 
282 
383 
Other operations and maintenance
427 
411 
828 
829 
Provision for Callaway construction and operating license
69 
0 
69 
0 
Depreciation and amortization
200 
183 
393 
364 
Taxes other than income taxes
116 
114 
241 
241 
Total operating expenses
1,164 
1,097 
2,464 
2,445 
Operating Income
237 
322 
493 
568 
Other Income and Expenses:
 
 
 
 
Miscellaneous income
16 1
21 1
35 1
39 1
Miscellaneous expense
6 1
4 1
17 1
13 1
Total other income (expense)
10 
17 
18 
26 
Interest Charges
89 
89 
177 
181 
Income Before Income Taxes
158 
250 
334 
413 
Income Taxes
59 
99 
125 
163 
Income from Continuing Operations
99 
151 
209 
250 
Income (Loss) from Discontinued Operations, Net of Taxes (Note 12)
52 
(1)
52 
(2)
Net Income (Loss)
151 
150 
261 
248 
Pension and other postretirement benefit plan activity, net of income taxes (benefit)
4 
3 
4 
3 
Comprehensive Income
154 
152 
262 
248 
Less: Net Income (Loss) Attributable to Noncontrolling Interests:
 
 
 
 
Net Income from Continuing Operations Attributable to Noncontrolling Interests
1 
1 
3 
3 
Net Income (Loss):
 
 
 
 
Continuing Operations
98 
150 
206 
247 
Discontinued Operations
52 
(1)
52 
(2)
Net Income (Loss)
150 
149 
258 
245 
Earnings Per Share, Basic [Abstract]
 
 
 
 
Continuing Operations
$ 0.40 
$ 0.62 
$ 0.85 
$ 1.02 
Discontinued Operations
$ 0.21 
$ (0.01)
$ 0.21 
$ (0.01)
Earnings Per Share, Basic
$ 0.61 
$ 0.61 
$ 1.06 
$ 1.01 
Dividends per Common Share
$ 0.41 
$ 0.40 
$ 0.82 
$ 0.80 
Average Common Shares Outstanding - Basic
242.6 
242.6 
242.6 
242.6 
Union Electric Company
 
 
 
 
Operating Revenues:
 
 
 
 
Electric
859 
871 
1,601 
1,620 
Gas
24 
28 
82 
96 
Other Revenue, Net
1 
1 
1 
1 
Total operating revenues
884 
900 
1,684 
1,717 
Operating Expenses:
 
 
 
 
Fuel
205 
198 
411 
402 
Purchased power
19 
29 
58 
64 
Gas purchased for resale
7 
11 
38 
51 
Other operations and maintenance
229 
221 
440 
446 
Provision for Callaway construction and operating license
69 
0 
69 
0 
Depreciation and amortization
124 
117 
242 
233 
Taxes other than income taxes
85 
81 
165 
159 
Total operating expenses
738 
657 
1,423 
1,355 
Operating Income
146 
243 
261 
362 
Other Income and Expenses:
 
 
 
 
Miscellaneous income
12 
16 
23 
30 
Miscellaneous expense
2 
2 
5 
6 
Total other income (expense)
10 
14 
18 
24 
Interest Charges
55 
54 
110 
106 
Income Before Income Taxes
101 
203 
169 
280 
Income Taxes
39 
76 
65 
105 
Net Income (Loss)
62 
127 
104 
175 
Other Comprehensive Income
0 
0 
0 
0 
Comprehensive Income
62 
127 
104 
175 
Net Income (Loss):
 
 
 
 
Net Income (Loss)
62 
127 
104 
175 
Earnings Per Share, Basic [Abstract]
 
 
 
 
Preferred Stock Dividends
1 
1 
2 
2 
Net Income Available to Common Stockholder
61 
126 
102 
173 
Ameren Illinois Company
 
 
 
 
Operating Revenues:
 
 
 
 
Electric
386 
364 
776 
717 
Gas
127 
155 
482 
576 
Total operating revenues
513 
519 
1,258 
1,293 
Operating Expenses:
 
 
 
 
Purchased power
87 
86 
189 
167 
Gas purchased for resale
39 
67 
244 
331 
Other operations and maintenance
202 
195 
404 
395 
Depreciation and amortization
73 
64 
146 
127 
Taxes other than income taxes
29 
32 
72 
78 
Total operating expenses
430 
444 
1,055 
1,098 
Operating Income
83 
75 
203 
195 
Other Income and Expenses:
 
 
 
 
Miscellaneous income
4 
5 
11 
8 
Miscellaneous expense
2 
1 
7 
5 
Total other income (expense)
2 
4 
4 
3 
Interest Charges
33 
29 
66 
59 
Income Before Income Taxes
52 
50 
141 
139 
Income Taxes
20 
21 
55 
56 
Net Income (Loss)
32 
29 
86 
83 
Pension and other postretirement benefit plan activity, net of income taxes (benefit)
(1)
(1)
(2)
(2)
Comprehensive Income
31 
28 
84 
81 
Net Income (Loss):
 
 
 
 
Net Income (Loss)
32 
29 
86 
83 
Earnings Per Share, Basic [Abstract]
 
 
 
 
Preferred Stock Dividends
1 
1 
2 
2 
Net Income Available to Common Stockholder
$ 31 
$ 28 
$ 84 
$ 81 
Consolidated Statement of Income (Loss) (Parenthetical) (USD $)
In Millions, unless otherwise specified
3 Months Ended 6 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Jun. 30, 2014
Pension and other postretirement benefit plan activity, tax expense (benefit)
$ 4 
$ 3 
$ 4 
$ 3 
Ameren Illinois Company
 
 
 
 
Pension and other postretirement benefit plan activity, tax expense (benefit)
$ 0 
$ 0 
$ (1)
$ (1)
Consolidated Statement of Comprehensive Income (Loss) (USD $)
In Millions, unless otherwise specified
3 Months Ended 6 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Jun. 30, 2014
Statement of Comprehensive Income [Abstract]
 
 
 
 
Income from Continuing Operations
$ 99 
$ 151 
$ 209 
$ 250 
Other Comprehensive Income from Continuing Operations, Net Of Taxes
 
 
   
   
Other Comprehensive Income from Continuing Operations, Net of Taxes
 
 
 
 
Pension and other postretirement benefit plan activity, net of income taxes (benefit)
4 
3 
4 
3 
Comprehensive Income from Continuing Operations
103 
154 
213 
253 
Less: Comprehensive Income from Continuing Operations Attributable to Noncontrolling Interests
1 
1 
3 
3 
Comprehensive Income from Continuing Operations Attributable to Ameren Corporation
102 
153 
210 
250 
Income (Loss) from Discontinued Operations, Net of Taxes
52 
(1)
52 
(2)
Other Comprehensive Loss from Discontinued Operations, Net of Taxes
0 
0 
0 
0 
Comprehensive Income (Loss) from Discontinued Operations Attributable to Ameren Corporation
52 
(1)
52 
(2)
Comprehensive Income
$ 154 
$ 152 
$ 262 
$ 248 
Consolidated Statement of Comprehensive Income (Loss) Consolidated Statement of Income (Parenthetical) (USD $)
In Millions, unless otherwise specified
3 Months Ended 6 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Jun. 30, 2014
Statement of Comprehensive Income [Abstract]
 
 
 
 
Pension and other postretirement benefit plan activity, tax expense (benefit)
$ 4 
$ 3 
$ 4 
$ 3 
Consolidated Balance Sheet (USD $)
In Millions, unless otherwise specified
Jun. 30, 2015
Dec. 31, 2014
Current Assets:
 
 
Cash and cash equivalents
$ 2 
$ 5 
Accounts receivable - trade (less allowance for doubtful accounts)
456 
423 
Unbilled revenue
302 
265 
Miscellaneous accounts and notes receivable
112 
81 
Materials and supplies
500 
524 
Current regulatory assets
223 
295 
Current accumulated deferred income taxes, net
286 
352 
Other current assets
95 
86 
Assets of discontinued operations (Note 12)
15 
15 
Total current assets
1,991 
2,046 
Property and Plant, Net
17,986 
17,424 
Investments and Other Assets:
 
 
Nuclear decommissioning trust fund
555 
549 
Goodwill
411 
411 
Regulatory assets
1,560 
1,582 
Other assets
649 
664 
Total investments and other assets
3,175 
3,206 
TOTAL ASSETS
23,152 
22,676 
Current Liabilities:
 
 
Current maturities of long-term debt
395 
120 
Short-term Debt
886 
714 
Accounts and wages payable
486 
711 
Taxes accrued
126 
46 
Interest accrued
98 
85 
Current regulatory liabilities
120 
106 
Other current liabilities
413 
434 
Liabilities of discontinued operations (Note 12)
32 
33 
Total current liabilities
2,556 
2,249 
Long-term Debt, Net
5,981 
6,120 
Deferred Credits and Other Liabilities:
 
 
Accumulated deferred income taxes, net
3,931 
3,923 
Accumulated deferred investment tax credits
64 
64 
Regulatory liabilities
1,912 
1,850 
Asset retirement obligations
589 
396 
Pension and other postretirement benefits
689 
705 
Other deferred credits and liabilities
524 
514 
Total deferred credits and other liabilities
7,709 
7,452 
Commitments and Contingencies
   
   
Stockholders' Equity:
 
 
Common Stock
2 
2 
Other paid-in capital
5,606 
5,617 
Retained earnings
1,161 
1,103 
Accumulated other comprehensive income (loss)
(5)
(9)
Stockholder's equity
6,764 
6,713 
Noncontrolling Interest
142 
142 
Total equity
6,906 
6,855 
TOTAL LIABILITIES AND EQUITY
23,152 
22,676 
Union Electric Company
 
 
Current Assets:
 
 
Cash and cash equivalents
0 
1 
Accounts receivable - trade (less allowance for doubtful accounts)
227 
190 
Accounts receivable - affiliates
13 
65 
Unbilled revenue
213 
146 
Miscellaneous accounts and notes receivable
54 
35 
Materials and supplies
371 
347 
Current regulatory assets
133 
163 
Other current assets
89 
92 
Total current assets
1,100 
1,039 
Property and Plant, Net
11,017 
10,867 
Investments and Other Assets:
 
 
Nuclear decommissioning trust fund
555 
549 
Regulatory assets
660 
695 
Other assets
389 
391 
Total investments and other assets
1,604 
1,635 
TOTAL ASSETS
13,721 
13,541 
Current Liabilities:
 
 
Current maturities of long-term debt
266 
120 
Short-term Debt
38 
97 
Accounts and wages payable
183 
405 
Accounts payable - affiliates
43 
56 
Taxes accrued
151 
32 
Interest accrued
73 
58 
Current regulatory liabilities
58 
18 
Other current liabilities
124 
117 
Total current liabilities
936 
903 
Long-term Debt, Net
3,869 
3,879 
Deferred Credits and Other Liabilities:
 
 
Accumulated deferred income taxes, net
2,826 
2,806 
Accumulated deferred investment tax credits
61 
61 
Regulatory liabilities
1,188 
1,147 
Asset retirement obligations
582 
389 
Pension and other postretirement benefits
275 
274 
Other deferred credits and liabilities
30 
30 
Total deferred credits and other liabilities
4,962 
4,707 
Commitments and Contingencies
   
   
Stockholders' Equity:
 
 
Common Stock
511 
511 
Other paid-in capital
1,784 
1,569 
Preferred stock
80 
80 
Retained earnings
1,579 
1,892 
Stockholder's equity
3,954 
4,052 
TOTAL LIABILITIES AND EQUITY
13,721 
13,541 
Ameren Illinois Company
 
 
Current Assets:
 
 
Cash and cash equivalents
0 
1 
Accounts receivable - trade (less allowance for doubtful accounts)
207 
212 
Accounts receivable - affiliates
8 
22 
Unbilled revenue
89 
119 
Miscellaneous accounts and notes receivable
11 
9 
Materials and supplies
129 
177 
Current regulatory assets
89 
129 
Current accumulated deferred income taxes, net
159 
160 
Other current assets
10 
15 
Total current assets
702 
844 
Property and Plant, Net
6,416 
6,165 
Investments and Other Assets:
 
 
Goodwill
411 
411 
Regulatory assets
893 
883 
Other assets
78 
78 
Total investments and other assets
1,382 
1,372 
TOTAL ASSETS
8,500 
8,381 
Current Liabilities:
 
 
Current maturities of long-term debt
129 
0 
Short-term Debt
12 
32 
Borrowings from money pool
25 
15 
Accounts and wages payable
229 
207 
Accounts payable - affiliates
43 
50 
Taxes accrued
10 
17 
Interest accrued
25 
24 
Customer deposits
73 
77 
Mark-to-market derivative liabilities
35 
42 
Current environmental remediation
43 
52 
Current regulatory liabilities
53 
84 
Other current liabilities
80 
100 
Total current liabilities
757 
700 
Long-term Debt, Net
2,112 
2,241 
Deferred Credits and Other Liabilities:
 
 
Accumulated deferred income taxes, net
1,454 
1,408 
Regulatory liabilities
724 
703 
Pension and other postretirement benefits
292 
277 
Environmental remediation
198 
199 
Other deferred credits and liabilities
221 
192 
Total deferred credits and other liabilities
2,889 
2,779 
Commitments and Contingencies
   
   
Stockholders' Equity:
 
 
Common Stock
0 
0 
Other paid-in capital
1,980 
1,980 
Preferred stock
62 
62 
Retained earnings
694 
611 
Accumulated other comprehensive income (loss)
6 
8 
Stockholder's equity
2,742 
2,661 
TOTAL LIABILITIES AND EQUITY
$ 8,500 
$ 8,381 
Consolidated Balance Sheet (Parenthetical) (USD $)
In Millions, except Per Share data, unless otherwise specified
Jun. 30, 2015
Dec. 31, 2014
Accounts receivable - trade allowance for doubtful accounts
$ 21 
$ 21 
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 
8 
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
$ 13 
$ 13 
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
6 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Cash Flows From Operating Activities:
 
 
Net income (loss)
$ 261 
$ 248 
(Income) loss from discontinued operations, net of taxes
(52)
2 
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
 
 
Provision for Callaway construction and operating license
69 
0 
Depreciation and amortization
387 
349 
Amortization of nuclear fuel
47 
47 
Amortization of debt issuance costs and premium/discounts
11 
11 
Deferred income taxes and investment tax credits, net
116 
178 
Allowance for equity funds used during construction
(11)1
(16)1
Stock-based compensation costs
14 
15 
Other
(13)
(8)
Changes in assets and liabilities:
 
 
Receivables
(80)
(62)
Materials and supplies
25 
35 
Accounts and wages payable
(180)
(180)
Taxes accrued
81 
68 
Regulatory assets and liabilities
65 
(98)
Assets, other
25 
54 
Liabilities, other
(27)
(21)
Pension and other postretirement benefits
28 
21 
Counterparty collateral, net
2 
15 
Net cash provided by operating activities – continuing operations
768 
658 
Net cash used in operating activities – discontinued operations
(1)
(4)
Net cash provided by operating activities
767 
654 
Cash Flows From Investing Activities:
 
 
Capital expenditures
(846)
(883)
Nuclear fuel expenditures
(28)
(26)
Purchases of securities - nuclear decommissioning trust fund
(117)
(290)
Sales and maturities of securities - nuclear decommissioning trust fund
110 
283 
Proceeds from Notes Receivable
10 
70 
Contributions to Note Receivable
(7)
(78)
Other
3 
2 
Net cash used in investing activities – continuing operations
(875)
(922)
Net cash provided by investing activities – discontinued operations
0 
152 
Net cash used in investing activities
(875)
(770)
Cash Flows From Financing Activities:
 
 
Dividends on common stock
(199)
(194)
Dividends paid to noncontrolling interest holders
(3)
(3)
Short-term debt, net
172 
425 
Redemptions of Long-term Debt
(114)
(692)
Issuances of Long-term Debt
249 
598 
Capital issuance costs
(2)
(4)
Other
2 
2 
Net cash provided by (used in) financing activities – continuing operations
105 
132 
Net cash used in financing activities - discontinued operations
0 
0 
Net cash provided by financing activities
105 
132 
Net change in cash and cash equivalents
(3)
16 
Cash and cash equivalents at beginning of period
5 
30 
Cash and cash equivalents at end of period
2 
46 
Union Electric Company
 
 
Cash Flows From Operating Activities:
 
 
Net income (loss)
104 
175 
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
 
 
Provision for Callaway construction and operating license
69 
0 
Depreciation and amortization
238 
220 
Amortization of nuclear fuel
47 
47 
Amortization of debt issuance costs and premium/discounts
3 
4 
Deferred income taxes and investment tax credits, net
27 
61 
Allowance for equity funds used during construction
(9)
(15)
Changes in assets and liabilities:
 
 
Receivables
(80)
(97)
Materials and supplies
(24)
0 
Accounts and wages payable
(180)
(163)
Taxes accrued
123 
(65)
Regulatory assets and liabilities
63 
(49)
Assets, other
16 
43 
Liabilities, other
35 
40 
Pension and other postretirement benefits
14 
11 
Net cash provided by operating activities
446 
212 
Cash Flows From Investing Activities:
 
 
Capital expenditures
(289)
(375)
Nuclear fuel expenditures
(28)
(26)
Purchases of securities - nuclear decommissioning trust fund
(117)
(290)
Sales and maturities of securities - nuclear decommissioning trust fund
110 
283 
Other
(4)
(5)
Net cash used in investing activities
(328)
(413)
Cash Flows From Financing Activities:
 
 
Dividends on common stock
(415)
(155)
Dividends on preferred stock
(2)
(2)
Short-term debt, net
(59)
185 
Money pool borrowings, net
0 
(44)
Redemptions of Long-term Debt
(114)
(104)
Issuances of Long-term Debt
249 
350 
Capital contribution from parent
224 
0 
Capital issuance costs
(2)
(2)
Net cash provided by financing activities
(119)
228 
Net change in cash and cash equivalents
(1)
27 
Cash and cash equivalents at beginning of period
1 
1 
Cash and cash equivalents at end of period
0 
28 
Ameren Illinois Company
 
 
Cash Flows From Operating Activities:
 
 
Net income (loss)
86 
83 
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
 
 
Depreciation and amortization
144 
125 
Amortization of debt issuance costs and premium/discounts
7 
6 
Deferred income taxes and investment tax credits, net
45 
58 
Allowance for equity funds used during construction
(2)
(1)
Other
(5)
(4)
Changes in assets and liabilities:
 
 
Receivables
57 
36 
Materials and supplies
48 
36 
Accounts and wages payable
20 
2 
Taxes accrued
(6)
(5)
Regulatory assets and liabilities
(1)
(46)
Assets, other
8 
10 
Liabilities, other
(29)
(22)
Pension and other postretirement benefits
12 
7 
Counterparty collateral, net
0 
15 
Net cash provided by operating activities
386 
301 
Cash Flows From Investing Activities:
 
 
Capital expenditures
(379)
(436)
Other
4 
4 
Net cash used in investing activities
(375)
(432)
Cash Flows From Financing Activities:
 
 
Dividends on preferred stock
(2)
(2)
Short-term debt, net
(20)
105 
Money pool borrowings, net
10 
(56)
Redemptions of Long-term Debt
0 
(163)
Issuances of Long-term Debt
0 
248 
Capital issuance costs
0 
(2)
Proceeds from Advances for Construction
0 
2 
Net cash provided by financing activities
(12)
132 
Net change in cash and cash equivalents
(1)
1 
Cash and cash equivalents at beginning of period
1 
1 
Cash and cash equivalents at end of period
$ 0 
$ 2 
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, administered by the FERC. 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.
Ameren has various other subsidiaries that conduct activities such as the provision of shared services. Ameren also has a subsidiary, ATXI, that operates a FERC rate-regulated electric transmission business. ATXI is developing MISO-approved electric transmission projects, including the Illinois Rivers, Spoon River, and Mark Twain projects. Ameren is also pursuing projects to improve electric transmission system reliability within Ameren Missouri's and Ameren Illinois' service territories as well as competitive electric transmission investment opportunities outside of these territories, including investments outside of MISO.
The operating results, assets, and liabilities of the Elgin, Gibson City, Grand Tower, Meredosia, and Hutsonville energy centers have been presented separately as discontinued operations for all periods presented in this report. Unless otherwise stated, these notes to Ameren’s financial statements exclude discontinued operations for all periods presented. See Note 12 - Divestiture Transactions and Discontinued Operations in this report for additional information regarding the discontinued operations presentation and Note 16 - Divestiture Transactions and Discontinued Operations under Part II, Item 8, of the Form 10-K for additional information regarding Ameren’s divestiture of New AER in December 2013.
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 presentation of our results. The preparation of financial statements in conformity with GAAP requires management to make certain estimates and assumptions. Such estimates and assumptions affect reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the dates of financial statements, and the reported amounts of revenues and expenses during the reported periods. Actual results could differ from those estimates. 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
The following table provides a reconciliation of the beginning and ending carrying amount of AROs for the six months ended June 30, 2015:
 
Ameren
Missouri
 
Ameren
Illinois(a)
 
Ameren
 
Balance at December 31, 2014
$
389

 
$
7

 
$
396

 
Accretion in 2015(b)
11

 
(c)

 
11

 
Change in estimates(d)
182

 
(c)

 
182

 
Balance at June 30, 2015
$
582

 
$
7

 
$
589

 
(a)
Included in “Other deferred credits and liabilities” on the balance sheet.
(b)
Accretion expense was recorded as an increase to regulatory assets.
(c)
Less than $1 million.
(d)
The ARO increase resulted in a corresponding increase recorded to “Property and Plant, Net.” During the first quarter of 2015, Ameren and Ameren Missouri increased their AROs related to the decommissioning of the Callaway energy center by $99 million to reflect the 2015 cost study and funding analysis filed with the MoPSC, extension of the estimated operating life until 2044, and a reduction in the discount rate assumption. See Note 10 - Callaway Energy Center for additional information. In addition, during the second quarter of 2015, as a result of new federal regulations, Ameren and Ameren Missouri recorded an increase of $79 million to their AROs associated with CCR storage facilities. See Note 9 - Commitments and Contingencies for additional information. Also during the second quarter of 2015, Ameren and Ameren Missouri increased their AROs by $4 million due to a change in the estimated retirement dates of the Meramec and Rush Island energy centers as a result of the MoPSC’s April 2015 electric rate order.
Stock-based Compensation
A summary of nonvested performance share units at June 30, 2015, and changes during the six months ended June 30, 2015, under the 2006 Incentive Plan and the 2014 Incentive Plan are presented below:
 
Number of Performance Share Units
Weighted-average Fair Value Per Performance Share Unit
Nonvested at January 1, 2015
1,162,377

$
35.35

Granted(a)
567,240

52.88

Forfeitures
(1,944
)
34.75

Vested(b)
(85,694
)
46.79

Nonvested at June 30, 2015
1,641,979

$
40.81

(a)
Performance share units granted to certain executive and nonexecutive officers and other eligible employees in 2015 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 2015 under the 2014 Incentive Plan was determined to be $52.88, which was based on Ameren’s closing common share price of $46.13 at December 31, 2014, and lattice simulations. Lattice simulations are used to estimate expected share payout based on Ameren’s total stockholder return for a three-year performance period relative to the designated peer group beginning January 1, 2015. The simulations can produce a greater fair value for the performance share unit than the applicable closing common share price because they include the weighted payout scenarios in which an increase in the share price has occurred. The significant assumptions used to calculate fair value also included a three-year risk-free rate of 1.10%, volatility of 12% to 18% for the peer group, and Ameren’s attainment of a three-year average earnings per share threshold during the performance period.
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 six months ended June 30, 2015 and 2014:
 
Three Months
 
Six Months
 
2015
 
2014
 
2015
 
2014
Ameren Missouri
$
41

 
$
39

 
$
75

 
$
73

Ameren Illinois
10

 
11

 
33

 
37

Ameren
$
51

 
$
50

 
$
108

 
$
110


Uncertain Tax Positions
The following table presents the total amount of reserves for unrecognized tax benefits (detriments) related to uncertain tax positions as of June 30, 2015, and December 31, 2014:
 
June 30, 2015
 
December 31, 2014
Ameren
$
—

 
$
54

Ameren Missouri
—

 
—

Ameren Illinois
—

 
(1
)

The following table presents the amount of reserves for unrecognized tax benefits, included in the table above, related to uncertain tax positions that, if recognized, would have impacted results of operations as of December 31, 2014:
 
 
 
December 31, 2014
Ameren

 
$
52

Ameren Missouri

 
—

Ameren Illinois

 
(1
)

In March 2015, a settlement was reached with the IRS for the 2012 tax year. Since there were no uncertain tax positions related to the 2012 tax year, as of December 31, 2014, this settlement did not impact the amount of recorded unrecognized tax benefits.
In June 2015, a settlement was reached with the IRS for the 2013 tax year. This settlement resolved the uncertain tax position associated with the final tax basis of New AER and the related tax benefit resulting from the divested merchant generation business. The settlement resulted in a reduction of Ameren’s unrecognized tax benefits of $53 million and an increase to net income from discontinued operations.
It is reasonably possible that events will occur during the next 12 months that would cause the total amount of our unrecognized tax benefits to fluctuate. We do not believe any such fluctuations would be material to our results of operations, financial position, or liquidity.
State income tax returns are generally subject to examination for a period of three years after filing. We do not currently have material state income tax issues under examination, administrative appeal, or litigation. The state impact of any federal changes remains subject to examination by various states for a period of up to one year after formal notification to the states.
Earnings Per Share
There were no material differences between Ameren’s basic and diluted earnings per share amounts for the three and six months ended June 30, 2015 and 2014. The assumed settlement of dilutive performance share units had an immaterial impact on earnings per share.
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 2014, FASB issued authoritative accounting guidance to clarify the principles for recognizing revenue and to develop a common revenue standard for GAAP. The guidance requires an entity to recognize an amount of revenue for the transfer of promised goods or services to customers that reflects the consideration which 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. In July 2015, FASB deferred the effective date of the new revenue standard to the first quarter of 2018. The guidance allows entities to choose one of two transition methods, either by applying the guidance retrospectively to each reporting period presented or by recording a cumulative effect adjustment to retained earnings in the period of initial adoption. The Ameren Companies are currently assessing the impacts of this guidance on their results of operations, financial positions and disclosures, as well as the transition method that they will use to adopt the guidance.
Presentation of Debt Issuance Costs
In April 2015, FASB issued authoritative accounting guidance to simplify the presentation of debt issuance costs. The guidance requires debt issuance costs to be presented in the balance sheet as a reduction to the associated debt liability. Currently, debt issuance costs are presented as a component of “Other assets” on the Ameren Companies’ balance sheets. As of June 30, 2015, Ameren, Ameren Missouri, and Ameren Illinois had debt issuance costs of $36 million, $20 million, and $16 million, respectively. The guidance will be effective for the Ameren Companies in the first quarter of 2016 and applied retrospectively, and it will not affect the Ameren Companies' results of operations or cash flows.
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
2015 Electric Rate Order
In April 2015, the MoPSC issued an order approving an increase in Ameren Missouri’s annual revenues for electric service of $122 million, including $109 million related to the increase in net energy costs above those included in base rates previously authorized by the MoPSC. The remaining increase of $13 million approved by the order was for non-energy costs. The revenue increase was based on a 9.53% return on common equity, a capital structure composed of 51.8% common equity, and a rate base of $7.0 billion to reflect investments through December 31, 2014. Rate changes consistent with the order became effective on May 30, 2015.
The order approved Ameren Missouri’s request for continued use of the FAC; however, it changed the FAC to exclude all transmission revenues and substantially all transmission charges. In addition, the order did not approve the continued use of the regulatory tracking mechanisms for storm costs and vegetation management and infrastructure inspection costs. These changes to Ameren Missouri’s recovery mechanisms are expected to contribute to regulatory lag. The order did approve the continued use of the regulatory tracking mechanisms for pension and other postretirement benefits, renewable energy standard costs, solar rebates, and uncertain tax positions that the MoPSC authorized in earlier electric rate orders.
In addition, the order approved a reduction to Noranda’s electric rates with an offsetting increase in electric rates for Ameren Missouri’s other customers. The rate shift is revenue neutral to Ameren Missouri.
In June 2015, Ameren Missouri filed a notice of appeal with the Missouri Court of Appeals, Western District, reserving the right to appeal the exclusion of all transmission revenues and substantially all transmission charges from the FAC, the reduction to Noranda’s electric rates, and the level of Noranda’s sales volume included in the MoPSC’s order.
MEEIA Filing
The MEEIA established a regulatory framework that, among other things, requires the MoPSC to ensure that a utility’s financial incentives are aligned to help customers use energy more efficiently, to provide timely cost recovery, and to provide earnings opportunities associated with cost effective energy efficiency programs. Missouri does not have a law mandating energy efficiency standards.
In August 2012, the MoPSC approved Ameren Missouri’s customer energy efficiency programs, net shared benefits, and performance incentive for 2013 through 2015. The 2013 through 2015 plan anticipated Ameren Missouri would invest up to $147 million in customer energy efficiency programs, realize $100 million of net shared benefits, and be eligible for a performance incentive that would allow Ameren Missouri the potential to earn additional revenues by achieving certain customer energy efficiency goals, including $19 million if 100% of the goals are achieved during the three-year period. From January 2013 through June 2015, Ameren Missouri invested $95 million in customer energy efficiency programs and realized $115 million of net shared benefits. Ameren Missouri has not recorded revenues associated with the performance incentive, but does expect to exceed 100% of the customer energy efficiency goals by the end of 2015, subject to MoPSC review, and therefore expects to recognize revenues in excess of $19 million within the next two years.
In December 2014, Ameren Missouri filed a three-year energy efficiency plan with the MoPSC under the MEEIA for 2016 to 2018 that included a portfolio of customer energy efficiency programs along with a rider to collect the program costs, net shared benefits, and a performance incentive from customers. Ameren Missouri amended this proposed plan in June 2015 when it filed a non-unanimous stipulation and agreement with certain intervenor parties. If this plan is approved by the MoPSC, beginning in January 2016, Ameren Missouri intends to invest up to $197 million over three years in the proposed customer energy efficiency programs. Ameren Missouri requested continued use of a MEEIA rider, which allows Ameren Missouri to collect from, or refund to, customers any difference in the actual amounts incurred and the amounts collected from customers for the MEEIA program costs and net shared benefits. Ameren Missouri anticipates net shared benefits would be approximately $65 million during this three-year plan. In addition, similar to its existing MEEIA energy efficiency plan that ends in December 2015, Ameren Missouri requested a performance incentive that would allow it to potentially earn additional revenues by achieving certain customer energy efficiency goals, including $30 million if 100% of the goals are achieved during the three-year period. Ameren Missouri would need to achieve at least 70% of its customer energy efficiency goals before it earns a performance incentive.
In July 2015, the MoPSC staff and certain intervenor parties filed a non-unanimous stipulation and agreement that is unacceptable to Ameren Missouri. Even if approved by the MoPSC, Ameren Missouri is not required to implement an energy efficiency plan. There is no date by which the MoPSC must act with respect to the proposed customer energy efficiency plan. Ameren Missouri cannot predict the level of investment, net shared benefits, or performance incentive that the MoPSC may approve, if any, or whether it will ultimately implement a customer energy efficiency plan for the three-year period beginning in January 2016.
Noranda Contract Notification
Ameren Missouri supplies electricity to Noranda’s aluminum smelter in southeast Missouri under a long-term power supply agreement. In May 2015, Ameren Missouri notified Noranda of its intent to terminate the agreement effective June 1, 2020. In order to remove Noranda from its service territory, Ameren Missouri would also be required to obtain approval from the MoPSC. Sales to Noranda represented 5% of Ameren Missouri’s total electric revenue in 2014.
ATXI Transmission Projects
In May 2015, the MoPSC granted ATXI a certificate of convenience and necessity for the seven mile portion of the Illinois Rivers project located in Missouri.
In June 2015, ATXI made a filing with the MoPSC requesting a certificate of convenience and necessity for the Mark Twain project. The Mark Twain project is a MISO-approved 100-mile transmission line located in northeast Missouri. A decision is expected from the MoPSC in 2016.
Illinois
IEIMA
Under the provisions of the IEIMA’s formula rate framework, which currently extends through 2019, Ameren Illinois’ electric delivery service rates are subject to an annual revenue requirement reconciliation to its actual 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 costs incurred. As of June 30, 2015, Ameren Illinois had recorded regulatory assets of $24 million, $102 million, and $36 million, to reflect its expected 2015, 2014, and 2013 revenue requirement reconciliation adjustments, with interest, respectively. Ameren Illinois is collecting the 2013 revenue requirement reconciliation adjustment from customers during 2015.
In April 2015, Ameren Illinois filed with the ICC its annual electric delivery service formula rate update to establish the revenue requirement used for 2016 customer rates. Pending ICC approval, and if approved as filed, Ameren Illinois’ update filing would result in a $110 million increase in Ameren Illinois’ electric delivery service revenue requirement, beginning in January 2016. This update reflects an increase to the annual formula rate based on 2014 actual costs and expected net plant additions for 2015, an increase to include the 2014 revenue requirement reconciliation adjustment, and a decrease for the conclusion of the 2013 revenue requirement reconciliation adjustment, which will be fully collected from customers in 2015. In July 2015, the ICC staff submitted its calculation of the revenue requirement included in Ameren Illinois’ update filing. The ICC staff recommended adjustments that would result in a $107 million increase in Ameren Illinois’ electric delivery service revenue requirement. An ICC decision on this April 2015 filing is expected by December 2015.
2015 Natural Gas Delivery Service Rate Case
In January 2015, Ameren Illinois filed a request with the ICC seeking approval to increase its annual revenues for natural gas delivery service. In an attempt to reduce regulatory lag, Ameren Illinois used a 2016 future test year in this proceeding. Additionally, the request included a proposal to implement a volume balancing adjustment for residential and small nonresidential customers. The volume balancing adjustment would ensure that changes in natural gas sales volumes do not result in an over or under collection of natural gas revenues for these rate classes. This case includes a capital structure composed of 50% common equity and a rate base of $1.2 billion. In July 2015, Ameren Illinois, the ICC staff, and certain other intervenors filed a stipulation and agreement with the ICC that would result in rates that are based on a return on common equity of 9.6%. The agreement does not address all the positions with all of the parties in the case. Based on the terms in the agreement and the unresolved positions in the case, Ameren Illinois' request seeks an annual revenue increase of $45 million, which Ameren Illinois estimates is materially identical to the ICC staff’s recommendation. The ICC staff and other intervenors did not oppose the volume balancing adjustment.
A decision by the ICC in this proceeding is required by December 2015, with new rates expected to be effective in January 2016. Ameren Illinois cannot predict the level of any delivery service rate changes the ICC may approve, whether the ICC will approve the volume balancing adjustment, or if the ICC will approve the agreement between Ameren Illinois, the ICC staff, and certain other intervenors. In addition, Ameren Illinois cannot predict whether any rate changes that may eventually be approved will be sufficient to enable Ameren Illinois to recover its costs and to earn a reasonable return on investments when the rate changes go into effect.
2013 Natural Gas Delivery Service Rate Order
In December 2013, the ICC issued a rate order that approved an increase in Ameren Illinois’ revenues for natural gas delivery service based on a 9.1% return on common equity. In March 2014, Ameren Illinois filed with the Appellate Court of the Fourth District of Illinois an appeal of the allowed return on common equity included in the ICC's order. Ameren Illinois sought a 10.4% return on common equity in this rate case. In June 2015, the Appellate Court of the Fourth District upheld the ICC’s rate order. Ameren Illinois does not intend to pursue any further appeals.
2015 ICC Purchased Power Reconciliation
In January 2015, the ICC issued an order that approved Ameren Illinois' reconciliation of revenues collected under its purchased power rider mechanism and Ameren Illinois' related cumulative power usage cost. In the first quarter of 2015, based on the January 2015 order, both Ameren and Ameren Illinois recorded a $15 million increase to electric revenues for the recovery of this cumulative power usage cost from electric customers.
ATXI Transmission Project
In July 2015, Illinois administrative law judges issued a proposed order that recommended a certificate of public convenience and necessity and project approval for the Spoon River project. The Spoon River project is a MISO-approved 35-mile transmission line to be constructed in northwest Illinois. A final order from the ICC is expected in 2015. A certificate of public convenience and necessity is required before ATXI can proceed with right-of-way acquisition.
Federal
Ameren Illinois Electric Transmission Rate Refund
In July 2012, the FERC issued an order concluding that Ameren Illinois improperly included acquisition premiums, including goodwill, in determining the common equity used in its electric transmission formula rate and thereby inappropriately recovered a higher amount from its electric transmission customers. The order required Ameren Illinois to make refunds to customers for such improperly included amounts.
In July 2015, the FERC approved a settlement agreement between Ameren Illinois and the affected customers. The settlement agreement requires Ameren Illinois to make refunds and payments of $8 million to electric transmission customers, of which $6 million was outstanding as of June 30, 2015. Ameren Illinois refunded $2 million in the second quarter of 2015 as part of a separate proceeding. The settlement agreement also requires Ameren Illinois to take other actions, such as reducing common equity for electric transmission ratemaking purposes on a prospective basis.
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 MISO transmission rate base under the MISO tariff to 9.15%. Currently, the FERC-allowed base return on common equity for MISO transmission owners is 12.38%. The FERC scheduled the case for hearing proceedings, requiring a proposed order from its administrative law judge to be issued no later than November 30, 2015, which will subsequently require FERC approval. The FERC has previously utilized a calculation to establish the allowed base return on common equity, which requires multiple inputs based on observable market data specific to the utility industry and broader macroeconomic data spanning unique time periods for each return on equity complaint case. We expect observable market data for the six months ended February 11, 2015 will be used in the November 2013 complaint case. As the maximum FERC-allowed refund period for the November 2013 complaint case ended in February 2015, another customer complaint case was filed in February 2015. The February 2015 complaint case seeks a reduction in the allowed base return on common equity for the FERC-regulated MISO transmission rate base under the MISO tariff to 8.67%. The FERC scheduled the February 2015 complaint case for hearing proceedings, requiring a proposed order from its administrative law judge to be issued no later than June 30, 2016, which will subsequently require FERC approval. We expect observable market data for the six months ended December 31, 2015 will be used in the February 2015 complaint case.
A 50 basis point reduction in the FERC-allowed return on common equity would reduce Ameren's and Ameren Illinois' annual earnings by an estimated $4 million and $2 million, respectively, based on 2015 projected rate base. Ameren and Ameren Illinois recorded current liabilities on their respective balance sheets as of June 30, 2015 representing their estimate of the potential refunds from the refund effective date of November 12, 2013. Ameren’s and Ameren Illinois’ recorded liabilities reflect the inputs used in the FERC’s calculation to establish the allowed base return on common equity, based on observable market data for the six months ended February 11, 2015, with respect to the November 2013 complaint case refund period, and based on current market data through June 30, 2015, with respect to the February 2015 complaint case refund period. Ameren’s and Ameren Illinois’ liabilities also reflect the 50 basis point adder discussed below, which became effective in early January 2015. Ameren Missouri did not record a liability as of June 30, 2015, and 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.
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. Collection of the incentive adder is deferred until the issuance of the final order addressing the initial MISO complaint case.
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. Due primarily to recent changes in vendor support for licensing efforts at the NRC, our 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 costs of the COL. Ameren Missouri intends to withdraw its COL application filed with the NRC in August 2015.
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 2012 Missouri Credit Agreement and the 2012 Illinois Credit Agreement, both of which expire on December 11, 2019, were not utilized for direct borrowings during the six months ended June 30, 2015, but were used to support commercial paper issuances and to issue letters of credit. Based on letters of credit issued under the 2012 Credit Agreements, as well as commercial paper outstanding, the aggregate amount of credit capacity available under the 2012 Credit Agreements to Ameren (parent), Ameren Missouri, and Ameren Illinois, collectively, at June 30, 2015, was $1.2 billion.
Commercial Paper
The following table presents commercial paper outstanding at Ameren (parent), Ameren Missouri, and Ameren Illinois as of June 30, 2015, and December 31, 2014:
  
June 30, 2015
 
December 31, 2014
Ameren (parent)
$
836

 
$
585

Ameren Missouri
38

 
97

Ameren Illinois
12

 
32

Ameren Consolidated
$
886

 
$
714

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 six months ended June 30, 2015 and 2014:
 
 
Ameren
(parent)
Ameren
Missouri
Ameren
Illinois
Ameren Consolidated
2015
 
 
 
 
 
 
Average daily commercial paper outstanding
 
$
754

 
$
84

$
5

$
843

Weighted-average interest rate
 
0.57
%
 
0.50
%
0.44
%
0.56
%
Peak commercial paper during period(a)
 
$
849

 
$
294

$
39

$
1,108

Peak interest rate
 
0.70
%
 
0.60
%
0.60
%
0.70
%
2014
 
 
 
 
 
 
Average daily commercial paper outstanding
 
$
328

 
$
146

$
242

$
607

Weighted-average interest rate
 
0.32
%
 
0.31
%
0.32
%
0.32
%
Peak commercial paper during period(a)
 
$
503

 
$
495

$
300

$
907

Peak interest rate
 
0.35
%
 
0.70
%
0.34
%
0.70
%

(a)
The timing of peak commercial paper issuances varies by company, and therefore the peak amounts presented by company might not equal the Ameren Consolidated peak commercial paper issuances for the period.
Indebtedness Provisions and Other Covenants
The information below is a summary of the Ameren Companies’ compliance with financial covenants in the 2012 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 2012 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 2012 Credit Agreements require each of Ameren, Ameren Missouri, and Ameren Illinois to maintain consolidated indebtedness of not more than 65% of its consolidated total capitalization pursuant to a defined calculation set forth in the agreements. As of June 30, 2015, the ratios of consolidated indebtedness to consolidated total capitalization, calculated in accordance with the 2012 Credit Agreements, were 51%, 50%, and 46%, for Ameren, Ameren Missouri, and Ameren Illinois, respectively. In addition, under the 2012 Illinois Credit Agreement and, by virtue of the cross-default provisions of the 2012 Missouri Credit Agreement, under the 2012 Missouri Credit Agreement, 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. However, the interest coverage requirement only applies at such times as Ameren does not have a senior long-term unsecured credit rating of at least Baa3 from Moody’s or BBB- from S&P. As of June 30, 2015, Ameren exceeded the 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 2012 Credit Agreement.
The 2012 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 2012 Credit Agreement will also be deemed to constitute a default of Ameren under such agreement. Defaults include a cross-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 2012 Credit Agreement). However, under the default provisions of the 2012 Credit Agreements, any default of Ameren under any 2012 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 2012 Credit Agreement. Further, the 2012 Credit Agreement default provisions provide that an Ameren default under any of the 2012 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 June 30, 2015.
Money Pools
Ameren has money pool agreements with and among its subsidiaries to coordinate and provide for certain short-term cash and working capital requirements.
Ameren Missouri, Ameren Illinois, and ATXI may participate in the utility money pool as both lenders and borrowers. Ameren and Ameren Services may participate in the utility money pool only as a lender. 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 2012 Credit Agreements and the commercial paper programs. The total amount available to the pool participants from the utility money pool at any given time is reduced by the amount of borrowings made by participants, but is increased to the extent that the pool participants advance surplus funds to the utility money pool or remit funds from other external sources. The availability of funds is also determined by funding requirement limits established by regulatory authorizations. Participants receiving a loan under the utility money pool agreement must repay the principal amount of such loan, together with accrued interest. The rate of interest depends on the composition of internal and external funds in the utility money pool. The average interest rate for borrowing under the utility money pool for both the three and six months ended June 30, 2015, was 0.08% (2014 - 0.19% and 0.29%, 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 three and six months ended June 30, 2015 and 2014.
Long-Term Debt And Equity Financings
LONG-TERM DEBT AND EQUITY FINANCINGS
LONG-TERM DEBT AND EQUITY
Ameren Missouri
In March 2015, Ameren Missouri received cash capital contributions of $224 million from Ameren (parent).
In April 2015, Ameren Missouri issued $250 million of 3.65% senior secured notes due April 15, 2045, with interest payable semiannually on April 15 and October 15 of each year, beginning October 15, 2015. Ameren Missouri received proceeds of $247 million, which were used to repay outstanding short-term debt, including short-term debt that Ameren Missouri incurred in connection with the repayment of $114 million of its 4.75% senior secured notes that matured on April 1, 2015.
Indenture Provisions and Other Covenants
Ameren Missouri’s and Ameren Illinois’ indentures, credit facilities, and articles of incorporation include covenants and provisions related to issuances of first mortgage bonds and preferred stock. Ameren Missouri and Ameren Illinois are required to meet certain ratios to issue additional first mortgage bonds and preferred stock. A failure to achieve these ratios would not result in a default under these covenants and provisions, but would restrict the companies’ ability to issue bonds or preferred stock. The following table summarizes the required and actual interest coverage ratios, and dividend coverage ratios, and bonds and preferred stock issuable as of June 30, 2015, 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
 
3.5
$
3,305
 
≥2.5
 
94.4
$
2,095
 
Ameren Illinois
 
≥2.0
 
6.7
 
3,533
(d) 
≥1.5
 
2.8
 
203
(e) 
(a)
Coverage required on the annual interest charges on first mortgage bonds outstanding and to be issued. Coverage is not required in certain cases when additional first mortgage bonds are issued on the basis of retired bonds.
(b)
Amount of bonds issuable based either on required coverage ratios or unfunded property additions, whichever is more restrictive. The amounts shown also include bonds issuable based on retired bond capacity of $946 million and $204 million at Ameren Missouri and Ameren Illinois, respectively.
(c)
Coverage required on the annual dividend on preferred stock outstanding and to be issued, as required in the respective company’s articles of incorporation.
(d)
Amount of bonds issuable by Ameren Illinois based on unfunded property additions and retired bonds solely under the former IP mortgage indenture. The amount of bonds issuable by Ameren Illinois is also subject to the lien restrictions contained in the 2012 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 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 June 30, 2015, Ameren Illinois had 53% 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 June 30, 2015, none of the Ameren Companies had any off-balance-sheet financing arrangements, other than operating leases entered into in the ordinary course of business. None of the Ameren Companies expect to engage in any significant off-balance-sheet financing arrangements in the near future. See Note 12 - Divestiture Transactions and Discontinued Operations for Ameren (parent) guarantees and letters of credit issued to support New AER based on the transaction agreement with IPH.
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 six months ended June 30, 2015 and 2014:
 
Three Months
 
Six Months
 
 
2015
 
2014
 
2015
 
2014
 
Ameren:(a)
 
 
 
 
 
 
 
 
Miscellaneous income:
 
 
 
 
 
 
 
 
Allowance for equity funds used during construction
$
6

 
$
9

 
$
11

 
$
16

 
Interest income on industrial development revenue bonds
6

 
7

 
13

 
14

 
Interest income
4

 
2

 
8

 
5

 
Other
—

 
3

 
3

 
4

 
Total miscellaneous income
$
16

 
$
21

 
$
35

 
$
39

 
Miscellaneous expense:
 
 
 
 
 
 
 
 
Donations
$
2

 
$
1

 
$
10

 
$
6

 
Other
4

 
3

 
7

 
7

 
Total miscellaneous expense
$
6

 
$
4

 
$
17

 
$
13

 
Ameren Missouri:
 
 
 
 
 
 
 
 
Miscellaneous income:
 
 
 
 
 
 
 
 
Allowance for equity funds used during construction
$
5

 
$
8

 
$
9

 
$
15

 
Interest income on industrial development revenue bonds
6

 
7

 
13

 
14

 
Interest income
1

 
1

 
1

 
1

 
Total miscellaneous income
$
12

 
$
16

 
$
23

 
$
30

 
Miscellaneous expense:
 
 
 
 
 
 
 
 
Donations
$
1

 
$
1

 
$
3

 
$
3

 
Other
1

 
1

 
2

 
3

 
Total miscellaneous expense
$
2

 
$
2

 
$
5

 
$
6

 
Ameren Illinois:
 
 
 
 
 
 
 
 
Miscellaneous income:
 
 
 
 
 
 
 
 
Allowance for equity funds used during construction
$
1

 
$
1

 
$
2

 
$
1

 
Interest income
3

 
1

 
7

 
3

 
Other
—

 
3

 
2

 
4

 
Total miscellaneous income
$
4

 
$
5

 
$
11

 
$
8

 
Miscellaneous expense:
 
 
 
 
 
 
 
 
Donations
$
1

 
$
—

 
$
4

 
$
3

 
Other
1

 
1

 
3

 
2

 
Total miscellaneous expense
$
2

 
$
1

 
$
7

 
$
5

 
(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 June 30, 2015, and December 31, 2014. As of June 30, 2015, these contracts ran through October 2017, March 2021, May 2032, and December 2016 for fuel oils, natural gas, power, and uranium, respectively.
  
Quantity (in millions, except as indicated)
 
2015
2014
Commodity
Ameren Missouri
Ameren Illinois
Ameren
Ameren Missouri
Ameren Illinois
Ameren
Fuel oils (in gallons)(a)
39

(b)

39

50

(b)

50

Natural gas (in mmbtu)
29

127

156

28

108

136

Power (in megawatthours)
1

10

11

1

11

12

Uranium (pounds in thousands)
316

(b)

316

332

(b)

332

(a)
Fuel oils consist of heating oil and ultra-low-sulfur diesel.
(b)
Not applicable.
Authoritative accounting guidance regarding derivative instruments requires that all contracts considered to be derivative instruments be recorded on the balance sheet at their fair values, unless the NPNS exception applies. See Note 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 does not qualify for the NPNS exception, we review the contract to determine if it qualifies for hedge accounting. We also consider whether gains or losses resulting from such derivatives qualify for regulatory deferral. Derivative contracts that qualify for regulatory deferral are recorded at fair value, with changes in fair value recorded as regulatory assets or regulatory liabilities in the period in which the change occurs. We believe derivative losses and gains deferred as regulatory assets and regulatory liabilities are probable of recovery or refund through future rates charged to customers. Regulatory assets and regulatory liabilities are amortized to operating income as related losses and gains are reflected in rates charged to customers. Therefore, gains and losses on these derivatives have no effect on operating income. As of June 30, 2015, and December 31, 2014, all contracts that qualify for hedge accounting 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 instruments, none of which were designated as hedging instruments, as of June 30, 2015, and December 31, 2014:
 
Balance Sheet Location
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
2015
 
 
 
 
 
 
Fuel oils
Other current assets
 
$
1

 
$
—

 
$
1

Natural gas
Other assets
 
—

 
1

 
1

Power
Other current assets
 
29

 
—

 
29

 
Total assets
 
$
30

 
$
1

 
$
31

Fuel oils
Other current liabilities
 
$
14

 
$
—

 
$
14

 
Other deferred credits and liabilities
 
5

 
—

 
5

Natural gas
MTM derivative liabilities
 
(a)

 
24

 
(a)

 
Other current liabilities
 
4

 
—

 
28

 
Other deferred credits and liabilities
 
7

 
14

 
21

Power
MTM derivative liabilities
 
(a)

 
11

 
(a)

 
Other current liabilities
 
2

 
—

 
13

 
Other deferred credits and liabilities
 
—

 
154

 
154

Uranium
Other current liabilities
 
2

 
—

 
2

 
Total liabilities
 
$
34

 
$
203

 
$
237

2014
 
 
 
 
 
 
Fuel oils
Other current assets
 
$
2

 
$
—

 
$
2

Natural gas
Other current assets
 
1

 
1

 
2

Power
Other current assets
 
15

 
—

 
15

 
Total assets
 
$
18

 
$
1

 
$
19

Fuel oils
Other current liabilities
 
$
22

 
$
—

 
$
22

 
Other deferred credits and liabilities
 
7

 
—

 
7

Natural gas
MTM derivative liabilities
 
(a)

 
31

 
(a)

 
Other current liabilities
 
6

 
—

 
37

 
Other deferred credits and liabilities
 
6

 
13

 
19

Power
MTM derivative liabilities
 
(a)

 
11

 
(a)

 
Other current liabilities
 
3

 
—

 
14

 
Other deferred credits and liabilities
 
—

 
131

 
131

Uranium
Other current liabilities
 
2

 
—

 
2

 
Total liabilities
 
$
46

 
$
186

 
$
232


(a)
Balance sheet line item not applicable to registrant.

The following table presents the cumulative amount of pretax net gains (losses) on all derivative instruments deferred in regulatory assets or regulatory liabilities as of June 30, 2015, and December 31, 2014:
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
2015
 
 
 
 
 
Fuel oils derivative contracts(a)
$
(19
)
 
$
—

 
$
(19
)
Natural gas derivative contracts(b)
(11
)
 
(37
)
 
(48
)
Power derivative contracts(c)
27

 
(165
)
 
(138
)
Uranium derivative contracts(d)
(2
)
 
—

 
(2
)
2014
 
 
 
 
 
Fuel oils derivative contracts
$
(29
)
 
$
—

 
$
(29
)
Natural gas derivative contracts
(11
)
 
(43
)
 
(54
)
Power derivative contracts
12

 
(142
)
 
(130
)
Uranium derivative contracts
(2
)
 
—

 
(2
)
(a)
Represents net losses associated with fuel oils derivative contracts at Ameren Missouri. These contracts are a partial hedge of Ameren Missouri’s rail transportation surcharges for coal through December 2017. Current gains deferred as regulatory liabilities include $1 million at Ameren and Ameren Missouri. Current losses deferred as regulatory assets include $14 million at Ameren and Ameren Missouri.
(b)
Represents net losses associated with natural gas derivative contracts. These contracts are a partial hedge of natural gas requirements through March 2021 at Ameren and Ameren Missouri and through October 2018 at Ameren Illinois. Current losses deferred as regulatory assets include $28 million, $4 million, and $24 million at Ameren, Ameren Missouri, and Ameren Illinois, respectively.
(c)
Represents net gains (losses) associated with power derivative contracts. These contracts are a partial hedge of power price requirements through May 2032 at Ameren and Ameren Illinois and through December 2016 at Ameren Missouri. Current gains deferred as regulatory liabilities include $29 million at Ameren and Ameren Missouri. Current losses deferred as regulatory assets include $13 million, $2 million, and $11 million at Ameren, Ameren Missouri, and Ameren Illinois, respectively.
(d)
Represents net losses on uranium derivative contracts at Ameren Missouri. These contracts are a partial hedge of Ameren Missouri’s uranium requirements through January 2017. Current losses deferred as regulatory assets include $2 million at Ameren and Ameren Missouri.
Derivative instruments are subject to various credit-related losses in the event of nonperformance by counterparties to the transaction. Exchange-traded contracts are supported by the financial and credit quality of the clearing members of the respective exchanges and have nominal credit risk. In all other transactions, we are exposed to credit risk. Our credit risk management program involves establishing credit limits and collateral requirements for counterparties, using master netting arrangements or similar agreements, and reporting daily exposure to senior management.
We believe that entering into master netting arrangements or similar agreements mitigates the level of financial loss that could result from default by allowing net settlement of derivative assets and liabilities. We generally enter into the following master netting arrangements: (1) the International Swaps and Derivatives Association Agreement, a standardized financial natural gas and electric contract; (2) the Master Power Purchase and Sale Agreement, created by the Edison Electric Institute and the National Energy Marketers Association, a standardized contract for the purchase and sale of wholesale power; and (3) the North American Energy Standards Board Inc. Agreement, a standardized contract for the purchase and sale of natural gas. These master netting arrangements allow the counterparties to net settle sale and purchase transactions. Further, collateral requirements are calculated at the master netting arrangement or similar agreement level by counterparty.
The following table provides the recognized gross derivative balances and the net amounts of those derivatives subject to an enforceable master netting arrangement or similar agreement as of June 30, 2015, and December 31, 2014:
 
 
 
 
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
2015
 
 
 
 
 
 
 
 
Assets:
 
 
 
 
 
 
 
 
Ameren Missouri
 
$
30

 
$
3

 
$
—

 
$
27

Ameren Illinois
 
1

 
—

 
—

 
1

Ameren
 
$
31

 
$
3

 
$
—

 
$
28

Liabilities:
 
 
 
 
 
 
 
 
Ameren Missouri
 
$
34

 
$
3

 
$
2

 
$
29

Ameren Illinois
 
203

 
—

 
—

 
203

Ameren
 
$
237

 
$
3

 
$
2

 
$
232

2014
 
 
 
 
 
 
 
 
Assets:
 
 
 
 
 
 
 
 
Ameren Missouri
 
$
18

 
$
5

 
$
—

 
$
13

Ameren Illinois
 
1

 
—

 
—

 
1

Ameren
 
$
19

 
$
5

 
$
—

 
$
14

Liabilities:
 
 
 
 
 
 
 
 
Ameren Missouri
 
$
46

 
$
5

 
$
5

 
$
36

Ameren Illinois
 
186

 
—

 
—

 
186

Ameren
 
$
232

 
$
5

 
$
5

 
$
222

(a)
Cash collateral received reduces gross asset balances and is included in “Other current liabilities” and “Other deferred credits and liabilities” on the balance sheet. Cash collateral posted reduces gross liability balances and is included in “Other current assets” and “Other assets” on the balance sheet.
Concentrations of Credit Risk
In determining our concentrations of credit risk related to derivative instruments, we review our individual counterparties and categorize each counterparty into groupings according to the primary business in which each engages. We calculate maximum exposures based on the gross fair value of financial instruments, including NPNS and other accrual contracts. These exposures are presented on a gross basis, which include affiliate exposure not eliminated at the consolidated Ameren level. As of June 30, 2015, if counterparty groups were to fail completely to perform on contracts, Ameren, Ameren Missouri, and Ameren Illinois' maximum exposures were $11 million, $11 million, and $- million, respectively. 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 June 30, 2015, the potential loss after consideration of the application of master netting arrangements or similar agreements and collateral held for Ameren, Ameren Missouri, and Ameren Illinois was $11 million, $11 million, and $- million, respectively.
Derivative Instruments with Credit Risk-Related Contingent Features
Our commodity contracts contain collateral provisions tied to the Ameren Companies’ credit ratings. If we were to experience an adverse change in our credit ratings, or if a counterparty with reasonable grounds for uncertainty regarding performance of an obligation requested adequate assurance of performance, additional collateral postings might be required. The following table presents, as of June 30, 2015, the aggregate fair value of all derivative instruments with credit risk-related contingent features in a gross liability position, the cash collateral posted, and the aggregate amount of additional collateral that could be required to be posted with counterparties. 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 June 30, 2015, and (2) those counterparties with rights to do so requested collateral.
 
Aggregate Fair Value of
Derivative Liabilities(a)
 
Cash
Collateral Posted
 
Potential Aggregate Amount of
Additional Collateral Required(b)
2015
 
 
 
 
 
Ameren Missouri
$
80

 
$
3

 
$
73

Ameren Illinois
77

 
—

 
72

Ameren
$
157

 
$
3

 
$
145

(a)
Prior to consideration of master netting arrangements or similar agreements and including NPNS and other accrual contract exposures.
(b)
As collateral requirements with certain counterparties are based on master netting arrangements or similar agreements, the aggregate amount of additional collateral required to be posted is determined after consideration of the effects of such arrangements.
Fair Value Measurements
FAIR VALUE MEASUREMENTS
FAIR VALUE MEASUREMENTS
Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. We use various methods to determine fair value, including market, income, and cost approaches. With these approaches, we adopt certain assumptions that market participants would use in pricing the asset or liability, including assumptions about market risk or the risks inherent in the inputs to the valuation. Inputs to valuation can be readily observable, market-corroborated, or unobservable. We use valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs. Authoritative accounting guidance established a fair value hierarchy that prioritizes the inputs used to measure fair value.
All financial assets and liabilities carried at fair value are classified and disclosed in one of 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 for the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy as of June 30, 2015:
 
 
Fair Value
 
 
 
Weighted Average
 
 
Assets
Liabilities
Valuation Technique(s)
Unobservable Input
Range
Level 3 Derivative asset and liability - commodity contracts(a):
 
 
 
Ameren
Fuel oils
$
1

$
(2
)
Option model
Volatilities(%)(b)
32 - 50
37
 
 
 
 
Discounted cash flow
Ameren Missouri credit risk(%)(b)(c)
0.40
(d)
 
Natural gas
—

(1
)
Discounted cash flow
Nodal basis($/mmbtu)(e)
(0.60) - 0
(0.40)
 
 
 
 
 
Counterparty credit risk(%)(b)(c)
0.21 - 2.01
0.83
 
 
 
 
 
Ameren Illinois credit risk(%)(b)(c)
0.40
(d)
 
Power(f)
29

(167
)
Discounted cash flow
Average forward peak and off-peak pricing - forwards/swaps($/MWh)(g)
26 - 45
31
 
 
 
 
 
Estimated auction price for FTRs($/MW)(e)
(1,006) - 1,606
184
 
 
 
 
 
Nodal basis($/MWh)(e)
(11) - (1)
(3)
 
 
 
 
 
Counterparty credit risk(%)(b)(c)
0.39 - 13.86
8.64
 
 
 
 
 
Ameren Missouri and Ameren Illinois credit risk(%)(b)(c)
0.40
(d)
 
 
 
 
Fundamental energy production model
Estimated future gas prices($/mmbtu)(e)
3 - 6
4
 
 
 
 
 
Escalation rate(%)(e)(h)
2
(d)
 
 
 
 
Contract price allocation
Estimated renewable energy credit costs($/credit)(e)
5 - 7
6
 
Uranium
—

(2
)
Discounted cash flow
Average forward uranium pricing($/pound)(e)
36 - 39
37
Ameren Missouri
Fuel oils
$
1

$
(2
)
Option model
Volatilities(%)(b)
32 - 50
37
 
 
 
 
Discounted cash flow
Ameren Missouri credit risk(%)(b)(c)
0.40
(d)
 
Power(f)
29

(2
)
Discounted cash flow
Average forward peak and off-peak pricing - forwards/swaps($/MWh)(b)
26 - 45
34
 
 
 
 
 
Estimated auction price for FTRs($/MW)(e)
(1,006) - 1,606
184
 
 
 
 
 
Nodal basis($/MWh)(b)
(11) - (4)
(9)
 
 
 
 
 
Counterparty credit risk(%)(b)(c)
0.39 - 13.86
8.64
 
Uranium
—

(2
)
Discounted cash flow
Average forward uranium pricing($/pound)(e)
36 - 39
37
Ameren Illinois
Natural gas
$
—

$
(1
)
Discounted cash flow
Nodal basis($/mmbtu)(e)
(0.60) - 0
(0.40)
 
 
 
 
 
Counterparty credit risk(%)(b)(c)
0.21 - 2.01
0.83
 
 
 
 
 
Ameren Illinois credit risk(%)(b)(c)
0.40
(d)
 
Power(f)
—

(165
)
Discounted cash flow
Average forward peak and off-peak pricing - forwards/swaps($/MWh)(e)
27 - 37
30
 
 
 
 
 
Nodal basis($/MWh)(e)
(6) - (1)
(3)
 
 
 
 
 
Ameren Illinois credit risk(%)(b)(c)
0.40
(d)
 
 
 
 
Fundamental energy production model
Estimated future gas prices($/mmbtu)(e)
3 - 6
4
 
 
 
 
 
Escalation rate(%)(e)(h)
2
(d)
 
 
 
 
Contract price allocation
Estimated renewable energy credit costs($/credit)(e)
5 - 7
6

(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 lower (higher) fair value measurement.
(c)
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.
(d)
Not applicable.
(e)
Generally, significant increases (decreases) in this input in isolation would result in a significantly higher (lower) fair value measurement.
(f)
Power valuations use visible third-party pricing evaluated by month for peak and off-peak demand through 2019. Valuations beyond 2019 use fundamentally modeled pricing by month for peak and off-peak demand.
(g)
The balance at Ameren is comprised of Ameren Missouri and Ameren Illinois power contracts, which respond differently to unobservable input changes due to their opposing positions. As such, refer to the power sensitivity analysis for each company above.
(h)
Escalation rate applies to power prices 2026 and beyond.
The following table describes the valuation techniques and unobservable inputs for the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy as of December 31, 2014:
 
 
Fair Value
 
 
 
 
Weighted
 
 
Assets
Liabilities
 
Valuation Technique(s)
Unobservable Input
Range
Average
Level 3 Derivative asset and liability – commodity contracts(a):
 
 
 
Ameren
Fuel oils
$
2

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

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

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

(2
)
 
Discounted cash flow
Average forward uranium pricing($/pound)(e)
35 - 40
36
Ameren Missouri
Fuel oils
$
2

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

(1
)
 
Option model
Volatilities(%)(b)
31 - 144
53
 
 
 
 
 
 
Nodal basis($/mmbtu)(e)
(0.40) - 0
(0.30)
 
 
 
 
 
Discounted cash flow
Nodal basis($/mmbtu)(e)
(0.10)
(d)
 
 
 
 
 
 
Counterparty credit risk(%)(b)(c)
0.57 - 13
5
 
 
 
 
 
 
Ameren Missouri credit risk(%)(b)(c)
0.43
(d)
 
Power(g)
11

(2
)
 
Discounted cash flow
Average forward peak and off-peak pricing – forwards/swaps($/MWh)(b)
27 - 50
32
 
 
 
 
 
 
Estimated auction price for FTRs($/MW)(e)
(1,833) - 2,743
171
 
 
 
 
 
 
Counterparty credit risk(%)(b)(c)
0.26
(d)
 
 
 
 
 
 
Ameren Missouri credit risk(%)(b)(c)
0.43
(d)
 
Uranium
—

(2
)
 
Discounted cash flow
Average forward uranium pricing($/pound)(e)
35 - 40
36
Ameren Illinois
Natural Gas
$
1

$
(1
)
 
Option model
Volatilities(%)(b)
50 - 144
94
 
 
 
 
 
 
Nodal basis($/mmbtu)(e)
(0.10) - 0
(0.10)
 
 
 
 
 
Discounted cash flow
Nodal basis($/mmbtu)(e)
(0.40) - 0.10
(0.20)
 
 
 
 
 
 
Counterparty credit risk(%)(b)(c)
0.43 - 2
0.83
 
 
 
 
 
 
Ameren Illinois credit risk(%)(b)(c)
0.43
(d)
 
Power(g)
—

(142
)
 
Discounted cash flow
Average forward peak and off-peak pricing – forwards/swaps($/MWh)(e)
27 - 38
32
 
 
 
 
 
 
Nodal basis($/MWh)(e)
(6) - 0
(2)
 
 
 
 
 
 
Ameren Illinois credit risk(%)(b)(c)
0.43
(d)
 
 
 
 
 
Fundamental energy production model
Estimated future gas prices($/mmbtu)(e)
4 - 5
4
 
 
 
 
 
 
Escalation rate(%)(e)(i)
0 - 1
1
 
 
 
 
 
Contract price allocation
Estimated renewable energy credit costs($/credit)(e)
5 - 7
6

(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 lower (higher) fair value measurement.
(c)
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.
(d)
Not applicable.
(e)
Generally, significant increases (decreases) in this input in isolation would result in a significantly higher (lower) fair value measurement.
(f)
Escalation rate applies to fuel oil prices 2017 and beyond.
(g)
Power valuations use visible third-party pricing evaluated by month for peak and off-peak demand through 2018. Valuations beyond 2018 use fundamentally modeled pricing by month for peak and off-peak demand.
(h)
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. As such, refer to the power sensitivity analysis for each company above.
(i)
Escalation rate applies to power prices 2026 and beyond.
In accordance with applicable authoritative accounting guidance, we consider nonperformance risk in our valuation of derivative instruments by analyzing the credit standing of our counterparties and considering any counterparty credit enhancements (e.g., collateral). The guidance also requires that the fair value measurement of liabilities reflect the nonperformance risk of the reporting entity, as applicable. Therefore, we have factored the impact of our credit standing, as well as any potential credit enhancements, into the fair value measurement of both derivative assets and derivative liabilities. Included in our valuation, and based on current market conditions, is a valuation adjustment for counterparty default derived from market data such as the price of credit default swaps, bond yields, and credit ratings. No gains or losses related to valuation adjustments for counterparty default risk were recorded at Ameren, Ameren Missouri, or Ameren Illinois in the first six months of 2015 or 2014. At June 30, 2015, the counterparty default risk liability valuation adjustment related to derivative contracts totaled $1 million, less than $1 million, and $1 million for Ameren, Ameren Missouri, and Ameren Illinois, respectively. At December 31, 2014, the counterparty default risk liability valuation adjustment related to derivative contracts totaled $1 million, less than $1 million, and $1 million for Ameren, Ameren Missouri, and Ameren Illinois, respectively.
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 June 30, 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):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
—

 
$
—

 
$
1

 
$
1

 
 
Natural gas
 
—

 
1

 
—

 
1

 
 
Power
 
—

 
—

 
29

 
29

 
 
Total derivative assets - commodity contracts
 
$
—

 
$
1

 
$
30

 
$
31

 
 
Nuclear decommissioning trust fund:
 
 
 
 
 
 
 
 
 
 
Cash and cash equivalents
 
$
6

 
$
—

 
$
—

 
$
6

 
 
Equity securities:
 
 
 
 
 
 
 
 
 
 
U.S. large capitalization
 
370

 
—

 
—

 
370

 
 
Debt securities:
 
 
 
 
 
 
 
 
 
 
Corporate bonds
 
—

 
59

 
—

 
59

 
 
U.S. treasury and agency securities
 
—

 
100

 
—

 
100

 
 
Other
 
—

 
22

 
—

 
22

 
 
Total nuclear decommissioning trust fund
 
$
376

 
$
181

 
$
—

 
$
557

(b) 
 
Total Ameren
 
$
376

 
$
182

 
$
30

 
$
588

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

 
$
—

 
$
1

 
$
1

 
 
Power
 
—

 
—

 
29

 
29

 
 
Total derivative assets - commodity contracts
 
$
—

 
$
—

 
$
30

 
$
30

 
 
Nuclear decommissioning trust fund:
 
 
 
 
 
 
 
 
 
 
Cash and cash equivalents
 
$
6

 
$
—

 
$
—

 
$
6

 
 
Equity securities:
 
 
 
 
 
 
 
 
 
 
U.S. large capitalization
 
370

 
—

 
—

 
370

 
 
Debt securities:
 
 
 
 
 
 
 
 
 
 
Corporate bonds
 
—

 
59

 
—

 
59

 
 
U.S. treasury and agency securities
 
—

 
100

 
—

 
100

 
 
Other
 
—

 
22

 
—

 
22

 
 
Total nuclear decommissioning trust fund
 
$
376

 
$
181

 
$
—

 
$
557

(b) 
 
Total Ameren Missouri
 
$
376

 
$
181

 
$
30

 
$
587

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

 
$
1

 
$
—

 
$
1

 
Liabilities:
 
 
 
 
 
 
 
 
 
 
Ameren
Derivative liabilities - commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
17

 
$
—

 
$
2

 
$
19

 
 
Natural gas
 
—

 
48

 
1

 
49

 
 
Power
 
—

 
—

 
167

 
167

 
 
Uranium
 
—

 
—

 
2

 
2

 
 
Total Ameren
 
$
17

 
$
48

 
$
172

 
$
237

 
Ameren
Derivative liabilities - commodity contracts(a):
 
 
 
 
 
 
 
 
 
Missouri
Fuel oils
 
$
17

 
$
—

 
$
2

 
$
19

 
 
Natural gas
 
—

 
11

 
—

 
11

 
 
Power
 
—

 
—

 
2

 
2

 
 
Uranium
 
—

 
—

 
2

 
2

 
 
Total Ameren Missouri
 
$
17

 
$
11

 
$
6

 
$
34

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

 
$
37

 
$
1

 
$
38

 
 
Power
 
—

 
—

 
165

 
165

 
 
Total Ameren Illinois
 
$
—

 
$
37

 
$
166

 
$
203

 
(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, 2014:
 
 
 
Quoted Prices in
Active Markets for
Identical Assets
or Liabilities
(Level 1)
 
Significant Other
Observable Inputs
(Level 2)
 
Significant Other
Unobservable
Inputs
(Level 3)
 
Total
 
Assets:
 
 
 
 
 
 
 
 
 
 
Ameren
Derivative assets - commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
—

 
$
—

 
$
2

 
$
2

 
 
Natural gas
 
—

 
1

 
1

 
2

 
 
Power
 
—

 
4

 
11

 
15

 
 
Total derivative assets - commodity contracts
 
$
—

 
$
5

 
$
14

 
$
19

 
 
Nuclear decommissioning trust fund:
 
 
 
 
 
 
 
 
 
 
Cash and cash equivalents
 
$
1

 
$
—

 
$
—

 
$
1

 
 
Equity securities:
 
 
 
 
 
 
 
 
 
 
U.S. large capitalization
 
364

 
—

 
—

 
364

 
 
Debt securities:
 
 
 
 
 
 
 
 
 
 
Corporate bonds
 
—

 
63

 
—

 
63

 
 
U.S. treasury and agency securities
 
—

 
102

 
—

 
102

 
 
Other
 
—

 
17

 
—

 
17

 
 
Total nuclear decommissioning trust fund
 
$
365

 
$
182

 
$
—

 
$
547

(b) 
 
Total Ameren
 
$
365

 
$
187

 
$
14

 
$
566

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

 
$
—

 
$
2

 
$
2

 
 
Natural gas
 
—

 
1

 
—

 
1

 
 
Power
 
—

 
4

 
11

 
15

 
 
Total derivative assets - commodity contracts
 
$
—

 
$
5

 
$
13

 
$
18

 
 
Nuclear decommissioning trust fund:
 
 
 
 
 
 
 
 
 
 
Cash and cash equivalents
 
$
1

 
$
—

 
$
—

 
$
1

 
 
Equity securities:
 
 
 
 
 
 
 
 
 
 
U.S. large capitalization
 
364

 
—

 
—

 
364

 
 
Debt securities:
 
 
 
 
 
 
 
 
 
 
Corporate bonds
 
—

 
63

 
—

 
63

 
 
U.S. treasury and agency securities
 
—

 
102

 
—

 
102

 
 
Other
 
—

 
17

 
—

 
17

 
 
Total nuclear decommissioning trust fund
 
$
365

 
$
182

 
$
—

 
$
547

(b) 
 
Total Ameren Missouri
 
$
365

 
$
187

 
$
13

 
$
565

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

 
$
—

 
$
1

 
$
1

 
Liabilities:
 
 
 
 
 
 
 
 
 
 
Ameren
Derivative liabilities - commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
21

 
$
—

 
$
8

 
$
29

 
 
Natural gas
 
1

 
53

 
2

 
56

 
 
Power
 
—

 
1

 
144

 
145

 
 
Uranium
 
—

 
—

 
2

 
2

 
 
Total Ameren
 
$
22

 
$
54

 
$
156

 
$
232

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

 
$
—

 
$
8

 
$
29

 
 
Natural gas
 
1

 
10

 
1

 
12

 
 
Power
 
—

 
1

 
2

 
3

 
 
Uranium
 
—

 
—

 
2

 
2

 
 
Total Ameren Missouri
 
$
22

 
$
11

 
$
13

 
$
46

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

 
$
43

 
$
1

 
$
44

 
 
Power
 
—

 
—

 
142

 
142

 
 
Total Ameren Illinois
 
$
—

 
$
43

 
$
143

 
$
186

 
(a)
The derivative asset and liability balances are presented net of counterparty credit considerations.
(b)
Balance excludes $2 million of receivables, payables, and accrued income, net.
The following table summarizes the changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the three months ended June 30, 2015:
  
 
Net derivative commodity contracts
 
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
Fuel oils:
 
 
 
 
 
 
Beginning balance at April 1, 2015
$
(6
)
$
(a)

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

 
(a)

 
1

Settlements
 
2

 
(a)

 
2

Transfers out of Level 3
 
2

 
(a)

 
2

Ending balance at June 30, 2015
$
(1
)
$
(a)

$
(1
)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2015
$
3

$
(a)

$
3

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

$
—

Purchases
 
—

 
(1
)
 
(1
)
Settlements
 
1

 
(1
)
 
—

Ending balance at June 30, 2015
$
—

$
(1
)
$
(1
)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2015
$
—

$
—

$
—

Power:
 
 
 
 
 
 
Beginning balance at April 1, 2015
$
4

$
(164
)
$
(160
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities
 
—

 
(4
)
 
(4
)
Purchases
 
29

 
—

 
29

Settlements
 
(6
)
 
3

 
(3
)
Ending balance at June 30, 2015
$
27

$
(165
)
$
(138
)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2015
$
1

$
(5
)
$
(4
)
Uranium:
 
 
 
 
 
 
Beginning balance at April 1, 2015
$
(1
)
$
(a)

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

 
(1
)
Ending balance at June 30, 2015
$
(2
)
$
(a)

$
(2
)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2015
$
(1
)
$
(a)

$
(1
)
(a)
Not applicable.

The following table summarizes the changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the three months ended June 30, 2014:
 
 
Net derivative commodity contracts
 
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
Fuel oils:
 
 
 
 
 
 
Beginning balance at April 1, 2014
$
1

$
(a)

$
1

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

 
(a)

 
1

Ending balance at June 30, 2014
$
2

$
(a)

$
2

Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2014
$
1

$
(a)

$
1

Natural gas:
 
 
 
 
 
 
Beginning balance at April 1, 2014
$
—

$
—

$
—

Purchases
 
—

 
1

 
1

Settlements
 
—

 
(1
)
 
(1
)
Ending balance at June 30, 2014
$
—

$
—

$
—

Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2014
$
—

$
—

$
—

Power:
 
 
 
 
 
 
Beginning balance at April 1, 2014
$
10

$
(120
)
$
(110
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities
 
(13
)
 
16

 
3

Purchases
 
34

 
—

 
34

Settlements
 
(15
)
 
1

 
(14
)
Transfers out of Level 3
 
(1
)
 
—

 
(1
)
Ending balance at June 30, 2014
$
15

$
(103
)
$
(88
)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2014
$
(1
)
$
15

$
14

Uranium:
 
 
 
 
 
 
Beginning balance at April 1, 2014
$
(5
)
$
(a)

$
(5
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities
 
(4
)
 
(a)

 
(4
)
Settlements
 
2

 
(a)

 
2

Ending balance at June 30, 2014
$
(7
)
$
(a)

$
(7
)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2014
$
(4
)
$
(a)

$
(4
)
(a)
Not applicable.

The following table summarizes the changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the six months ended June 30, 2015:
  
 
Net derivative commodity contracts
 
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
Fuel oils:
 
 
 
 
 
 
Beginning balance at January 1, 2015
$
(6
)
$
(a)

$
(6
)
Settlements
 
3

 
(a)

 
3

Transfers out of Level 3
 
2

 
(a)

 
2

Ending balance at June 30, 2015
$
(1
)
$
(a)

$
(1
)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2015
$
—

$
(a)

$
—

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

$
(1
)
Settlements
 
1

 
(1
)
 
—

Ending balance at June 30, 2015
$
—

$
(1
)
$
(1
)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2015
$
—

$
—

$
—

Power:
 
 
 
 
 
 
Beginning balance at January 1, 2015
$
9

$
(142
)
$
(133
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities
 
(2
)
 
(29
)
 
(31
)
Purchases
 
29

 
—

 
29

Settlements
 
(9
)
 
6

 
(3
)
Ending balance at June 30, 2015
$
27

$
(165
)
$
(138
)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2015
$
—

$
(29
)
$
(29
)
Uranium:
 
 
 
 
 
 
Beginning balance at January 1, 2015
$
(2
)
$
(a)

$
(2
)
Ending balance at June 30, 2015
$
(2
)
$
(a)

$
(2
)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2015
$
—

$
(a)

$
—

(a)
Not applicable.

The following table summarizes the changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the six months ended June 30, 2014:
  
 
Net derivative commodity contracts
 
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
Fuel oils:
 
 
 
 
 
 
Beginning balance at January 1, 2014
$
5

$
(a)

$
5

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

 
(1
)
Settlements
 
(2
)
 
(a)

 
(2
)
Ending balance at June 30, 2014
$
2

$
(a)

$
2

Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2014
$
—

$
(a)

$
—

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

$
—

$
—

Purchases
 
—

 
(1
)
 
(1
)
Settlements
 
—

 
1

 
1

Ending balance at June 30, 2014
$
—

$
—

$
—

Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2014
$
—

$
—

$
—

Power:
 
 
 
 
 
 
Beginning balance at January 1, 2014
$
19

$
(108
)
$
(89
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities
 
(18
)
 
4

 
(14
)
Purchases
 
34

 
—

 
34

Settlements
 
(20
)
 
1

 
(19
)
Ending balance at June 30, 2014
$
15

$
(103
)
$
(88
)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2014
$
(3
)
$
1

$
(2
)
Uranium:
 
 
 
 
 
 
Beginning balance at January 1, 2014
$
(6
)
$
(a)

$
(6
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities
 
(4
)
 
(a)

 
(4
)
Settlements
 
3

 
(a)

 
3

Ending balance at June 30, 2014
$
(7
)
$
(a)

$
(7
)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2014
$
(4
)
$
(a)

$
(4
)
(a)
Not applicable.
Transfers in or out of Level 3 represent either (1) existing assets and liabilities that were previously categorized as a higher level, but were recategorized to Level 3 because the inputs to the model became unobservable during the period or (2) existing assets and liabilities that were previously classified as Level 3, but were recategorized to a higher level because the lowest significant input became observable during the period. Transfers between Level 2 and Level 3 for power derivatives and between Level 1 and Level 3 for fuel oils were primarily caused by changes in availability of similar financial trades observable on electronic exchanges between the periods. Any reclassifications are reported as transfers out of Level 3 at the fair value measurement reported at the beginning of the period in which the changes occur. For the three and six months ended June 30, 2015 and 2014, there were no transfers between Level 1 and Level 2 related to derivative commodity contracts. The following table summarizes all transfers between fair value hierarchy levels related to derivative commodity contracts for the three and six months ended June 30, 2015, and 2014:
 
2015
2014
 
Ameren Missouri
Ameren Illinois
Ameren
Ameren Missouri
Ameren Illinois
Ameren
Three Months
 
 
 
 
 
 
Transfers out of Level 3 / Transfers into Level 1 - Fuel oils
$
2

$
—

$
2

$
—

$
—

$
—

Transfers out of Level 3 / Transfers into Level 2 - Power
—

—

—

(1
)
—

(1
)
Six Months
 
 
 
 
 
 
Transfers out of Level 3 / Transfers into Level 1 - Fuel oils
$
2

$
—

$
2

$
—

$
—

$
—


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 June 30, 2015, and December 31, 2014:
 
June 30, 2015
 
December 31, 2014
 
Carrying
Amount
 
Fair
Value
 
Carrying
Amount
 
Fair
Value
Ameren:(a)
 
 
 
 
 
 
 
Long-term debt and capital lease obligations (including current portion)
$
6,376

 
$
6,919

 
$
6,240

 
$
7,135

Preferred stock
142

 
122

 
142

 
122

Ameren Missouri:
 
 
 
 
 
 
 
Long-term debt and capital lease obligations (including current portion)
$
4,135

 
$
4,492

 
$
3,999

 
$
4,518

Preferred stock
80

 
73

 
80

 
73

Ameren Illinois:
 
 
 
 
 
 
 
Long-term debt
$
2,241

 
$
2,427

 
$
2,241

 
$
2,517

Preferred stock
62

 
49

 
62

 
49

(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 2015, Ameren Illinois used an RFP process, administered by the IPA, to procure energy products from June 1, 2015, through May 31, 2018. Ameren Missouri was among the winning suppliers in the energy product RFP process. As a result, in 2015, Ameren Missouri and Ameren Illinois entered into energy product agreements by which Ameren Missouri agreed to sell and Ameren Illinois agreed to purchase 667,000 megawatthours at an average price of $36 per megawatthour during the period of June 1, 2015, through June 30, 2017.
The following table presents the impact on Ameren Missouri and Ameren Illinois of related party transactions for the three and six months ended June 30, 2015 and 2014.
 
 
 
 
 
Three Months
 
Six Months
Agreement
Income Statement
Line Item
 
 
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
Missouri
 
Ameren
Illinois
Ameren Missouri power supply
Operating Revenues
 
2015
$
4

$
(a)

$
5

$
(a)

agreements with Ameren Illinois
 
 
2014
 
3

 
(a)

 
3

 
(a)

Ameren Missouri and Ameren Illinois
Operating Revenues
 
2015
 
7

 
1

 
13

 
2

rent and facility services
 
 
2014
 
4

 
1

 
9

 
1

Ameren Missouri and Ameren Illinois
Operating Revenues
 
2015
 
1

 
(b)

 
1

 
(b)

miscellaneous support services
 
 
2014
 
1

 
(b)

 
1

 
(b)

Total Operating Revenues
 
 
2015
$
12

$
1

$
19

$
2

 
 
 
2014
 
8

 
1

 
13

 
1

Ameren Illinois power supply
Purchased Power
 
2015
$
(a)

$
4

$
(a)

$
5

agreements with Ameren Missouri
 
 
2014
 
(a)

 
3

 
(a)

 
3

Ameren Illinois transmission
Purchased Power
 
2015
 
(a)

 
(b)

 
(a)

 
1

services with ATXI
 
 
2014
 
(a)

 
(b)

 
(a)

 
1

Total Purchased Power
 
 
2015
$
(a)

$
4

$
(a)

$
6

 
 
 
2014
 
(a)

 
3

 
(a)

 
4

Ameren Services support services
Other Operations and Maintenance
 
2015
$
32

$
30

$
66

$
59

agreement
 
 
2014
 
32

 
27

 
65

 
54

Money pool borrowings (advances)
Interest Charges/ Miscellaneous Income
 
2015
$
(b)

$
(b)

$
(b)

$
(b)

 
 
 
2014
 
(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 1 - Summary of Significant Accounting Policies, Note 2 - Rate and Regulatory Matters, Note 8 - Related Party Transactions, Note 10 - Callaway Energy Center, and Note 12 - Divestiture Transactions and Discontinued Operations in this report.
Callaway Energy Center
The following table presents insurance coverage at Ameren Missouri’s Callaway energy center at June 30, 2015. The property coverage and the nuclear liability coverage must be renewed on April 1 and January 1, respectively, of each year. Both coverages were renewed in 2015.
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) 
128

(b) 
 
$
13,361

(c) 
$
128

  
Property damage:
 
 
 
 
NEIL
$
2,750

(d) 
$
27

(e) 
European Mutual Association for Nuclear Insurance
500

(f) 
—

 
 
$
3,250

 
$
27

 
Replacement power:
 
 
 
 
NEIL
$
490

(g) 
$
10

(e) 
(a)
Provided through mandatory participation in an industrywide retrospective premium assessment program.
(b)
Retrospective premium under the Price-Anderson Act. This is subject to retrospective assessment with respect to a covered loss in excess of $375 million in the event of an incident at any licensed United States commercial reactor, payable at $19 million per year.
(c)
Limit of liability for each incident under the Price-Anderson liability provisions of the Atomic Energy Act of 1954, as amended. A company could be assessed up to $128 million per incident for each licensed reactor it operates with a maximum of $19 million per incident to be paid in a calendar year for each reactor. This limit is subject to change to account for the effects of inflation and changes in the number of licensed reactors.
(d)
NEIL provides $2.25 billion in property damage, decontamination, and premature decommissioning insurance for both radiation and nonradiation events. An additional $500 million is provided for radiation events only for a total of $2.75 billion.
(e)
All NEIL insured plants could be subject to assessments should losses exceed the accumulated funds from NEIL.
(f)
European Mutual Association for Nuclear Insurance provides $500 million in excess of the $2.75 billion and $2.25 billion property coverage for radiation and nonradiation events, respectively, provided by NEIL.
(g)
Provides replacement power cost insurance in the event of a prolonged accidental outage. Weekly indemnity up to $4.5 million for 52 weeks, which commences after the first twelve weeks of an outage, plus up to $3.6 million per week for a minimum of 71 weeks thereafter for a total not exceeding the policy limit of $490 million. Nonradiation events are sub-limited to $328 million.
The Price-Anderson Act is a federal law that limits the liability for claims from an incident involving any licensed United States commercial nuclear energy center. The limit is based on the number of licensed reactors. The limit of liability and the maximum potential annual payments are adjusted at least every five years for inflation to reflect changes in the Consumer Price Index. The most recent five-year inflationary adjustment became effective in September 2013. Owners of a nuclear reactor cover this exposure through a combination of private insurance and mandatory participation in a financial protection pool, as established by the Price-Anderson Act.
Losses resulting from terrorist attacks on nuclear facilities are covered under NEIL’s policies, subject to an industrywide aggregate policy 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
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 also have entered into various long-term commitments for purchased power and natural gas for distribution. For a complete listing of our obligations and commitments, see Note 15 - Commitments and Contingencies under Part II, Item 8 of the Form 10-K.
At June 30, 2015, total other obligations related to commitments for coal, natural gas, nuclear fuel, purchased power, methane gas, equipment, customer energy efficiency program expenditures and meter reading services, among other agreements, at Ameren, Ameren Missouri, and Ameren Illinois were $5,110 million, $3,247 million, and $1,822 million, respectively.
In April 2015, Ameren Illinois used an RFP process, administered by the IPA, to procure energy products from June 1, 2015, through May 31, 2018. Ameren Illinois contracted to purchase approximately 5,526,000 megawatthours of energy products for $185 million during this period. The procured energy products are included in Ameren’s and Ameren Illinois’ obligations discussed above. See Note 8 - Related Party Transactions in this report for additional information regarding energy product agreements between Ameren Missouri and Ameren Illinois as a result of this RFP process.
Environmental Matters
We are subject to various environmental laws and regulations enforced by federal, state, and local authorities. From the beginning phases of siting and development to the operation of existing or new electric generation, transmission and distribution facilities and natural gas storage, transmission and distribution facilities, our activities involve compliance with diverse environmental laws and regulations. These laws and regulations address emissions, discharges to water, water usage, impacts to air, land, and water, and chemical and waste handling. Complex and lengthy processes are required to obtain and renew approvals, permits, or licenses for new, existing or modified facilities. Additionally, the use and handling of various chemicals or hazardous materials require release prevention plans and emergency response procedures.
The EPA is developing and implementing environmental regulations that will have a significant impact on the electric utility industry. Over time, compliance with these regulations could be costly for certain companies, including Ameren Missouri, that operate coal-fired power plants. Significant new rules proposed or promulgated 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 of CCR and CCR landfills and impoundments; 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 waste water discharges from power plants and new regulations under the Clean Water Act that could require significant capital expenditures, such as modifications to water intake structures or new cooling towers at Ameren Missouri’s energy centers. Certain of these new and proposed regulations, if adopted, 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 the future regulations are unknown, the combined effects of the new and proposed environmental regulations could result in significant capital expenditures and increased operating costs for Ameren and Ameren Missouri. 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. 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 these costs would be recoverable through rates, subject to MoPSC prudence review, but the nature and timing of costs, as well as the applicable regulatory framework, could result in regulatory lag.
As of June 30, 2015, Ameren and Ameren Missouri estimate capital expenditures of $350 million to $400 million through 2019 to comply with existing environmental regulations. Considerable uncertainty remains in this estimate. 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. This estimate does not include the impacts of the Clean Power Plan’s reduction in emissions of CO2, but does include our preliminary estimate of the capital expenditures required for the CCR regulations that were published in April 2015, both of which are discussed below. The estimate also includes capital expenditures associated with MATS compliance discussed below.
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 Missouri has two scrubbers at its Sioux energy center, which are used to reduce SO2 emissions and other pollutants. Ameren Missouri's compliance plan assumes the installation of additional controls, including mercury control technology at multiple energy centers within its coal-fired fleet through 2019. However, Ameren Missouri continues to evaluate its operations and options to determine how to comply with the CSAPR, the MATS, and other recently finalized or proposed EPA regulations. Ameren Missouri may be required to install additional pollution controls within the next six to 10 years. In addition, Ameren Missouri is currently evaluating the recently finalized Clean Power Plan and potential compliance plans for the rule.
The following sections describe the more significant new or proposed environmental laws and rules and environmental enforcement and remediation matters that affect or could affect our operations.
Clean Air Act
Both federal and state laws require significant reductions in SO2 and NOx through either emission source reductions or the use and retirement of emission allowances. The CSAPR became effective on January 1, 2015, for SO2 and annual NOx reductions, and on May 1, 2015, for ozone season NOx reductions. There will be further emission reduction requirements in 2017 and potentially more in subsequent years. Ameren Missouri expects to have sufficiently reduced emissions and have sufficient allowances to avoid purchasing allowances to comply with CSAPR for 2015. To achieve compliance with CSAPR, Ameren Missouri operates two scrubbers at its Sioux energy center and burns ultra-low sulfur coal. Ameren Missouri does not expect to make additional capital investments to comply with the current CSAPR requirements. However, Ameren Missouri expects to incur additional operations and maintenance costs to lower its emissions at one or more of its energy centers for compliance with the CSAPR in future years. These higher operations and maintenance costs are expected to be collected from customers through the FAC or higher base rates.
In December 2011, the EPA issued the MATS under the Clean Air Act, which requires reductions in emissions of mercury and other hazardous air pollutants, such as acid gases, trace metals, and hydrogen chloride. The MATS do not require a specific control technology to achieve the emission reductions. The MATS apply to each unit at a coal-fired power plant. However, in certain cases, compliance can be achieved by averaging emissions from similar units at the same power plant. Compliance was required by April 2015 or, with a case-by-case extension, by April 2016. Ameren Missouri's Labadie and Meramec energy centers were granted extensions. In June 2015, the United States Supreme Court remanded a case challenging the MATS back to the United States Court of Appeals for the District of Columbia Circuit and ruled that the EPA must consider costs before deciding whether regulation of emissions of mercury and other hazardous air pollutants from power plants is appropriate and necessary. Unless the United States Court of Appeals for the District of Columbia Circuit acts to stay implementation of the MATS, Ameren Missouri expects to make additional capital investments at its Labadie and Meramec energy centers to comply with the MATS by April 2016. These capital expenditure investments are included in Ameren's and Ameren Missouri's estimate of capital expenditures to comply with existing environmental regulations above. In addition, Ameren Missouri is incurring additional operations and maintenance costs to lower its emissions at its energy centers in compliance with the MATS. These higher operations and maintenance costs are expected to be collected from customers through the FAC or higher base rates.
In December 2014, the EPA published its proposal to strengthen the 2008 national ambient air quality standard for ozone. A final standard is expected in October 2015, after which states that do not meet the standard must develop and implement plans to achieve compliance. Ameren Missouri is currently evaluating the proposed standard and the possible effects on its operations.
Greenhouse Gas Regulation
In August 2015, the EPA issued the finalized version of the Clean Power Plan, which sets forth CO2 emissions standards that will be applicable to existing power plants. The finalized regulations will become effective 60 days after publication in the Federal Register and differ significantly from the EPA’s originally proposed June 2014 rule.
Under the Clean Power Plan, Ameren Missouri expects to incur increased net fuel and operating costs, and new or accelerated capital expenditures, in addition to making modifications to existing operations in order to achieve compliance. The states of Missouri and Illinois are required to each significantly reduce their greenhouse gas emissions below 2005 levels by 2030. States are required to submit preliminary compliance plans to the EPA as early as 2016, although extensions until 2018 are available. The rule contains interim compliance periods which commence in 2022. Ameren Missouri is in the preliminary stage of evaluating the Clean Power Plan and the potential impacts to its operations, including those related to electric system reliability and its level of investment in customer energy efficiency programs. Significant uncertainty exists regarding the impact of the Clean Power Plan, as the finalized rule is different from the originally proposed rule and will be subject to legal challenges, which could result in the amount and timing of CO2 emissions standards being revised. Compliance measures could result in the closure or alteration of the operation of some of Ameren Missouri’s coal and natural gas-fired energy centers, which could result in increased operating costs. Ameren Missouri expects substantially all of these increased costs to be recoverable, subject to MoPSC prudence review, through higher rates to customers, which could be significant.
Also, in August 2015, the EPA issued final regulations that set CO2 emissions standards for new and modified power plants. These new standards establish separate emissions limits for new natural-gas fired plants and new coal-fired plants.
Federal and state legislation or regulations that mandate limits on the emission of greenhouse gases may result in significant increases in capital expenditures and operating costs, which could lead to increased liquidity needs and higher financing costs. These compliance costs could be prohibitive at some of Ameren Missouri’s energy centers. Mandatory limits on the emission of greenhouse gases 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 greenhouse gas limitations to the extent that the investments are reflected and recovered timely in rates charged to customers.
NSR and Clean Air Litigation
In January 2011, the Department of Justice, on behalf of the EPA, filed a complaint against Ameren Missouri in the United States District Court for the Eastern District of Missouri. The EPA's complaint, as amended in October 2013, alleges that in performing projects at its Rush Island coal-fired energy center in 2007 and 2010, Ameren Missouri violated provisions of the Clean Air Act and Missouri law. In January 2012, the district court granted, in part, Ameren Missouri's motion to dismiss various aspects of the EPA's penalty claims. The EPA's claims for unspecified injunctive relief remain. Ameren Missouri anticipates a trial of this case will occur in 2016. Ameren Missouri believes its defenses are meritorious and is defending itself vigorously. However, there can be no assurances that it will be successful in its efforts.
The ultimate resolution of this matter could have a material adverse effect on the future results of operations, financial position, and liquidity of Ameren and Ameren Missouri. A resolution could result in increased capital expenditures for the installation of pollution control equipment, increased operations and maintenance expenses, and penalties. We are unable to predict the ultimate resolution of these matters or the costs that might be incurred.
Clean Water Act
In August 2014, the EPA published the final rule applicable to cooling water intake structures at existing power plants. The rule requires a case-by-case evaluation and plan for reducing the mortality of aquatic organisms impinged on the facility’s intake screens or entrained through the plant's cooling water system. Implementation of this rule will be administered through each power plant’s water discharge permitting process. All of Ameren Missouri’s coal-fired and nuclear energy centers are subject to this rule. The rule could have an adverse effect on Ameren’s and Ameren Missouri’s results of operations, financial position, and liquidity if its implementation requires the installation of cooling towers or extensive modifications to the cooling water systems at our energy centers and if those investments are not recovered timely in electric rates charged to its customers.
In April 2013, the EPA announced its proposal to revise the effluent limitation guidelines applicable to steam electric generating units under the Clean Water Act. Effluent limitation guidelines are national standards for wastewater discharges to surface water that are based on the effectiveness of available control technology. The EPA's proposed rule raised several compliance options that would prohibit effluent discharges of certain, but not all, waste streams and impose more stringent limitations on certain components in wastewater discharges from power plants. If the rule is enacted as proposed, Ameren Missouri would be subject to the revised limitations beginning as early as July 1, 2017, but no later than July 1, 2022. The EPA is expected to issue final guidelines in September 2015.
Ash Management
In December 2014, the EPA issued regulations regarding the management and disposal of CCR, which will affect future CCR disposal and handling costs at Ameren Missouri's energy centers. The final CCR regulations were published in April 2015. The regulations allow for the management of CCR as a solid waste, as well as for its continued beneficial uses, such as recycling, which could reduce the amount to be disposed. The regulations also establish criteria regarding the structural integrity, location, and operation of CCR impoundments and landfills. They require groundwater monitoring, and closure of impoundments if the groundwater standards are not achieved. During the second quarter of 2015, Ameren and Ameren Missouri recorded an increase to their AROs associated with CCR storage facilities as a result of the new regulations. See Note 1 - Summary of Significant Accounting Policies in this report for additional information. Ameren Missouri's capital expenditure plan includes the cost of constructing landfills as part of its environmental compliance plan. Ameren Missouri expects certain of its ash ponds could be closed within the next five years.
The new regulations do not apply to inactive ash ponds at plants no longer in operation, such as Ameren’s Meredosia and Hutsonville energy centers.
Remediation
The Ameren Companies are involved in a number of remediation actions to clean up sites affected by hazardous substances, as required by federal and state law. Such laws require that responsible parties fund remediation actions regardless of their degree of fault, the legality of original disposal, or the ownership of a disposal site. Ameren Missouri and Ameren Illinois have each been identified by federal or state governments as a potentially responsible party at several contaminated sites.
As of June 30, 2015, Ameren Illinois owned or was otherwise responsible for 44 former MGP sites in Illinois, which are in various stages of investigation, evaluation, remediation, and closure. Ameren Illinois estimates it could substantially conclude remediation efforts at these sites by 2018. 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. To be recoverable, such costs must be prudently incurred. Costs are subject to annual review by the ICC. As of June 30, 2015, Ameren Illinois estimated the obligation related to these former MGP sites at $240 million to $309 million. Ameren and Ameren Illinois recorded a liability of $240 million to represent the estimated minimum obligation for these sites, as no other amount within the range was a better estimate.
The scope and extent to which these former MGP sites are remediated may increase as remediation efforts continue. Considerable uncertainty remains in these estimates, as many factors can influence the ultimate actual costs, including site specific unanticipated underground structures, the degree to which groundwater is encountered, regulatory changes, local ordinances, and site accessibility. The actual costs may vary substantially from these estimates.
Ameren Illinois formerly used an off-site landfill, which Ameren Illinois did not own, in connection with the operation of a previously-owned energy center. Ameren Illinois could be required to perform certain maintenance activities at that landfill, which is now closed. As of June 30, 2015, Ameren Illinois estimated the obligation related to the landfill at $0.5 million to $6 million. Ameren Illinois recorded a liability of $0.5 million to represent its estimated minimum obligation for this site, as no other amount within the range was a better estimate. Ameren Illinois is also responsible for the cleanup of some underground storage tanks and a water treatment plant in Illinois. As of June 30, 2015, Ameren Illinois recorded a liability of $0.7 million to represent its best estimate of the obligation for these sites.
In 2008, the EPA issued an administrative order to Ameren Missouri pertaining to a former coal tar distillery in St. Louis, Missouri operated by Koppers Company or its predecessor and successor companies. While Ameren Missouri is the current owner of the site, it did not conduct any of the manufacturing operations involving coal tar or its byproducts. Ameren Missouri, along with two other potentially responsible parties, have completed site investigation activities and have submitted their findings to the EPA. As of June 30, 2015, Ameren Missouri estimated its obligation at $2 million to $5 million. Ameren Missouri recorded a liability of $2 million to represent its estimated minimum obligation, as no other amount within the range was a better estimate.
Ameren Missouri also participated in the investigation of various sites located in Sauget, Illinois. In 2000, the EPA notified Ameren Missouri and numerous other companies, including Solutia, Inc., that former landfills and lagoons at those sites may contain soil and groundwater contamination. These sites are known as Sauget Area 2. From about 1926 until 1976, Ameren Missouri operated an energy center adjacent to Sauget Area 2. Ameren Missouri currently owns a parcel of property at Sauget Area 2 that was once used as a landfill.
In December 2013, the EPA issued its record of decision for Sauget Area 2 approving the investigation and the remediation alternatives recommended by the potentially responsible parties. Further negotiation among the potentially responsible parties will determine how to fund the implementation of the EPA-approved cleanup remedies. As of June 30, 2015, Ameren Missouri estimated its obligation related to Sauget Area 2 at $1 million to $2.5 million. Ameren Missouri recorded a liability of $1 million to represent its estimated minimum obligation for this site, as no other amount within the range was a better estimate.
In December 2012, Ameren Missouri signed an administrative order with the EPA and agreed to investigate soil and groundwater conditions at an Ameren Missouri-owned substation in St. Charles, Missouri. As of June 30, 2015, Ameren Missouri estimated and recorded a $1 million liability related to the remaining cleanup of the site.
Our operations or those of our predecessor companies involve the use of, disposal of, and in appropriate circumstances, the cleanup of substances regulated under environmental laws. We are unable to determine whether such practices will result in future environmental commitments or will affect our results of operations, financial position, or liquidity.
Pumped-storage Hydroelectric Facility Breach
In December 2005, there was a breach of the upper reservoir at Ameren Missouri's Taum Sauk pumped-storage hydroelectric energy center. The breach resulted in significant flooding in the local area, which damaged a state park. Ameren Missouri had liability insurance coverage for the Taum Sauk incident, subject to certain limits and deductibles.
In 2010, Ameren Missouri sued an insurance company that was providing Ameren Missouri with liability coverage on the date of the Taum Sauk incident. In the litigation, Ameren Missouri claims that the insurance company breached its duty to indemnify Ameren Missouri for losses resulting from the incident. In September 2014, the United States District Court for the Eastern District of Missouri ordered the case to be transferred to the United States District Court for the Southern District of New York. The transfer order was stayed pending Ameren Missouri’s October 2014 appeal of the order to the United States Court of Appeals for the Eight Circuit. In July 2015, the court of appeals upheld the order transferring the case to the United States District Court for the Southern District of New York, and the case was subsequently transferred.
As of June 30, 2015, Ameren Missouri had a net insurance receivable balance of $41 million. The insurance claim was $53 million as of June 30, 2015. Ameren Missouri expects to collect this receivable from the insurance company in the pending litigation described above. This receivable is included in “Other assets” on Ameren’s and Ameren Missouri’s balance sheets as of June 30, 2015. Ameren's and Ameren Missouri's results of operations, financial position, and liquidity could be adversely affected if Ameren Missouri's insurance receivable balance is not collected.
Asbestos-related Litigation
Ameren, Ameren Missouri, and Ameren Illinois have been named, along with numerous other parties, in a number of lawsuits filed by plaintiffs claiming varying degrees of injury from asbestos exposure at our current or former energy centers. Most have been filed in the Circuit Court of Madison County, Illinois. The total number of defendants named in each case varies, with 73 as the average number of parties as of June 30, 2015. Each lawsuit seeks unspecified damages that, if awarded at trial, typically would be shared among the various defendants.
The following table presents the pending asbestos-related lawsuits filed against the Ameren Companies as of June 30, 2015:
Ameren
 
Ameren
Missouri
 
Ameren
Illinois
 
Total(a)
1
 
28
 
36
 
49
(a)
Total does not equal the sum of the subsidiary unit lawsuits because some of the lawsuits name multiple Ameren entities as defendants.
As of June 30, 2015, Ameren, Ameren Missouri, and Ameren Illinois had liabilities of $8 million, $3 million, and $5 million, respectively, recorded to represent their best estimate of their obligations related to asbestos claims.
Ameren Illinois has a tariff rider to recover the costs of IP asbestos-related litigation claims, subject to the following terms: 90% of cash expenditures in excess of the amount included in base electric rates are to be recovered from a trust fund that was established when Ameren acquired IP. At June 30, 2015, the trust fund balance was $22 million, including accumulated interest. If cash expenditures are less than the amount in base rates, Ameren Illinois will contribute 90% of the difference to the trust fund. Once the trust fund is depleted, 90% of allowed cash expenditures in excess of base rates will be recovered through charges assessed to customers under the tariff rider. The rider will permit recovery from customers within IP’s historical service territory.
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 annually to review the nuclear waste fee against the cost of the nuclear waste disposal program and to propose to the United States Congress any fee adjustment necessary to offset the costs of the program. As required by the NWPA, Ameren Missouri and other utilities have entered into standard contracts with the DOE. Consistent with the NWPA and its standard contract, Ameren Missouri had historically collected one mill from its electric customers for each kilowatthour of electricity that it generated and sold from its Callaway energy center. Because the federal government is not meeting its disposal obligation, the collection of this fee is currently suspended.
Although both the NWPA and the standard contract stated that the DOE would begin to dispose of spent nuclear fuel by 1998, the DOE is not meeting its disposal obligation. Ameren Missouri has sufficient installed capacity at the Callaway energy center to store its spent nuclear fuel generated through 2020, and is constructing additional dry spent fuel storage capacity. 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 begin to dispose of spent nuclear fuel from commercial nuclear energy centers and fulfill its contractual obligations, Ameren Missouri and other nuclear energy center owners sued the DOE to recover costs, such as certain NRC fees and Missouri ad valorem taxes incurred for ongoing storage of their spent fuel. The lawsuit resulted in a settlement agreement that provides for annual recovery of additional spent fuel storage and related costs incurred from 2010 through 2016, with the ability to extend the recovery period as mutually agreed upon by the parties. Included in these reimbursements are costs related to a dry spent fuel storage facility that Ameren Missouri is constructing at its Callaway energy center. Ameren Missouri intends to begin transferring spent fuel assemblies to this facility in 2015. Ameren Missouri will continue to apply for reimbursement from the DOE for the cost to construct, operate, and decommission the dry spent fuel storage facility along with related allowable costs.
In March 2015, the NRC approved Ameren Missouri’s application to extend its Callaway energy center's operating license from 2024 to 2044.
Electric utility rates charged to customers provide for the recovery of the Callaway energy center's decommissioning costs, which include decontamination, dismantling, and site restoration costs, over the expected life of the nuclear energy center. Amounts collected from customers are deposited into the external nuclear decommissioning trust fund to provide for the Callaway energy center’s decommissioning. It is assumed that the Callaway energy center site will be decommissioned through the immediate dismantlement method and removed from service. Ameren and Ameren Missouri have recorded an ARO for the Callaway energy center decommissioning costs at fair value, which represents the present value of estimated future cash outflows. Annual decommissioning costs of $7 million are included in the costs used to establish electric rates for Ameren Missouri's customers. Every three years, the MoPSC requires Ameren Missouri to file an updated cost study and funding analysis for decommissioning its Callaway energy center. Following the NRC’s decision to approve Ameren Missouri’s operating license extension application, an updated cost study and a revised funding analysis were filed with the MoPSC in April 2015. Ameren Missouri’s April 2015 filing supported no change in electric service rates. There is no time requirement by which the MoPSC must issue an order regarding the decommissioning cost included in Ameren Missouri’s electric service rates. If the assumed return on trust assets is not earned, we believe that it is probable that any such earnings deficiency will be recovered in rates. The fair value of the trust fund for Ameren Missouri's Callaway energy center is reported as "Nuclear decommissioning trust fund" in Ameren's and Ameren Missouri's balance sheets. This amount is legally restricted and may be used only to fund the costs of nuclear decommissioning. Changes in the fair value of the trust fund are recorded as an increase or decrease to the nuclear decommissioning trust fund, with an offsetting adjustment to the related regulatory liability.
Retirement Benefits
RETIREMENT BENEFITS
RETIREMENT BENEFITS
Ameren’s pension plans are funded in compliance with income tax regulations and to meet federal funding or regulatory requirements. As a result, Ameren expects to fund its pension plans at a level equal to the greater of the pension expense or the legally required minimum contribution. Considering Ameren’s assumptions at June 30, 2015, the plan’s estimated investment performance through June 30, 2015, and Ameren’s pension funding policy, Ameren expects to make annual contributions of $25 million to $115 million through 2019, with aggregate estimated contributions of $290 million. These amounts are estimates which may change with actual investment performance, changes in interest rates, any pertinent changes in government regulations, and any voluntary contributions. Separately, our policy for postretirement benefits is primarily to fund the voluntary employees’ beneficiary association trusts to match the annual postretirement expense.
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 six months ended June 30, 2015 and 2014:
  
Pension Benefits
 
Postretirement Benefits
 
 
Three Months
 
Six Months
 
Three Months
 
Six Months
 
  
2015
 
2014
 
2015
 
2014
 
2015
 
2014
 
2015
 
2014
 
Service cost
$
22

 
$
19

 
$
46

 
$
40

 
$
6

 
$
4

 
$
11

 
$
9

 
Interest cost
43

 
42

 
87

 
91

 
12

 
12

 
24

 
25

 
Expected return on plan assets
(62
)
 
(57
)
 
(124
)
 
(114
)
 
(17
)
 
(16
)
 
(34
)
 
(32
)
 
Amortization of:
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Prior service benefit
—

 
—

 
—

 
—

 
(1
)
 
(1
)
 
(2
)
 
(2
)
 
Actuarial loss (gain)
19

 
12

 
37

 
24

 
2

 
(2
)
 
3

 
(3
)
 
Settlement loss
1

 
—

 
1

 
—

 
—

 
—

 
—

 
—

 
Net periodic benefit cost (benefit)
$
23

 
$
16

 
$
47

 
$
41

 
$
2

 
$
(3
)
 
$
2

 
$
(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 six months ended June 30, 2015 and 2014:
  
Pension Benefits
 
Postretirement Benefits
 
 
Three Months
 
Six Months
 
Three Months
 
Six Months
 
  
2015
 
2014
 
2015
 
2014
 
2015
 
2014
 
2015
 
2014
 
Ameren Missouri
$
13

 
$
8

 
$
28

 
$
25

 
$
3

 
$
1

 
$
4

 
$
2

 
Ameren Illinois
10

 
7

 
19

 
15

 
(1
)
 
(3
)
 
(2
)
 
(4
)
 
Other
—

 
1

 
—

 
1

 
—

 
(1
)
 
—

 
(1
)
 
Ameren(a)
$
23

 
$
16

 
$
47

 
$
41

 
$
2

 
$
(3
)
 
$
2

 
$
(3
)
 

(a)
Includes amounts for Ameren registrants and nonregistrant subsidiaries.
Divestiture Transactions and Discontinued Operations
DIVESTITURE TRANSACTIONS AND DISCONTINUED OPERATIONS
DIVESTITURE TRANSACTIONS AND DISCONTINUED OPERATIONS
On December 2, 2013, Ameren completed the divestiture of New AER to IPH in accordance with the transaction agreement between Ameren and IPH dated March 14, 2013, as amended by a letter agreement dated December 2, 2013. The transaction agreement with IPH, as amended, provided that if the Elgin, Gibson City, and Grand Tower gas-fired energy centers were subsequently sold by Medina Valley and if Medina Valley received additional proceeds from such sale, Medina Valley would pay Genco any proceeds from such sale, net of taxes and other expenses, in excess of the $137.5 million previously paid to Genco.
On January 31, 2014, Medina Valley completed the sale of the Elgin, Gibson City, and Grand Tower gas-fired energy centers to Rockland Capital for a total purchase price of $168 million. The agreement with Rockland Capital required $17 million of the purchase price to be held in escrow until January 31, 2016, to fund certain indemnity obligations, if any, of Medina Valley. The Rockland Capital escrow receivable balance and the corresponding payable due to Genco is reflected on Ameren's June 30, 2015 consolidated balance sheet in "Other current assets" and in "Other current liabilities," respectively. Medina Valley expects to pay Genco any remaining portion of the escrow balance on January 31, 2016. Ameren did not record a gain from its sale of the Elgin, Gibson City, and Grand Tower gas-fired energy centers.
Discontinued Operations Presentation
See Note 16 - Divestiture Transactions and Discontinued Operations under Part II, Item 8, of the Form 10-K for additional information related to disposal groups. All matters related to the final tax basis of New AER and the related tax benefit resulting from the divested merchant generation business have been resolved with the completion of the IRS’ audit for 2013. During the second quarter of 2015, based on the completion of the IRS audit, Ameren removed the reserve for unrecognized tax benefits recorded in 2013 and recognized a tax benefit from discontinued operations. See Note 1 - Summary of Significant Accounting Policies for additional information regarding the Ameren Companies’ uncertain tax positions.
The following table presents the components of discontinued operations in Ameren's consolidated statement of income for the three and six months ended June 30, 2015 and 2014:
 
Three Months
 
Six Months
 
2015
 
2014
 
2015
 
2014
Operating revenues
$
—

 
$
—

 
$
—

 
$
1

Operating benefits (expenses)
—

 
(1
)
 
3

 
(3
)
Operating income (loss) before income tax
—

 
(1
)
 
3

 
(2
)
Income tax benefit
52

 
—

 
49

 
—

Income (loss) from discontinued operations, net of taxes
$
52

 
$
(1
)
 
$
52

 
$
(2
)
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 June 30, 2015, and December 31, 2014:
 
June 30, 2015
 
December 31, 2014
Assets of discontinued operations
 
 
 
Accumulated deferred income taxes, net
$
15

 
$
15

Total assets of discontinued operations
$
15

 
$
15

Liabilities of discontinued operations
 
 
 
Accounts payable and other current obligations
$
2

 
$
1

Asset retirement obligations
30

 
32

Total liabilities of discontinued operations
$
32

 
$
33


Pursuant to the IPH transaction agreement, as amended, Ameren is obligated to pay up to $25 million for certain liabilities as of June 30, 2015, which were included in "Other current liabilities" on Ameren's June 30, 2015 consolidated balance sheet.
The note receivable from Marketing Company related to the cash collateral support provided to New AER was $9 million and $12 million at June 30, 2015, and December 31, 2014, respectively, and was reflected on Ameren's consolidated balance sheet in "Miscellaneous accounts and notes receivable.” This receivable is due to Ameren, with interest, on December 2, 2015, or sooner as cash collateral requirements are reduced. In addition, as of June 30, 2015, if Ameren’s credit ratings had been below investment grade, Ameren could have been required to post additional cash collateral in support of New AER in the amount of $19 million, which includes $6 million currently covered by Ameren guarantees discussed below. This cash collateral support is part of Ameren’s obligation to provide certain limited credit support to New AER until December 2, 2015, as discussed below.
Ameren Guarantees and Letters of Credit
The IPH transaction agreement, as amended, requires Ameren to maintain its financial obligations with respect to all credit support provided to New AER as of the December 2, 2013 closing date of the divestiture. Ameren must also provide such additional credit support as required by contracts entered into prior to the closing date, in each case until December 2, 2015. IPH shall indemnify Ameren for any payments Ameren makes pursuant to these credit support obligations if the counterparty does not return the posted collateral to Ameren. IPH's indemnification obligation is secured by certain AERG and Genco assets. In addition, Dynegy has provided a limited guarantee of $25 million to Ameren pursuant to which Dynegy will, among other things, guarantee IPH's indemnification obligations until December 2, 2015.
In addition to the $25 million of liabilities recorded on Ameren’s June 30, 2015 consolidated balance sheet, Ameren had a total of $79 million in guarantees outstanding for New AER that were not recorded on Ameren’s June 30, 2015 consolidated balance sheet. Almost all of these guarantees support Marketing Company for physically and financially settled power transactions with its counterparties that were in place at the December 2, 2013 closing of the divestiture, as well as for Marketing Company's clearing broker and other service agreements. If Marketing Company did not fulfill its obligations to these counterparties who had active open positions as of June 30, 2015, Ameren would have been required under its guarantees to provide $6 million to the counterparties. Also, at June 30, 2015, Ameren had issued letters of credit totaling $9 million as credit support on behalf of New AER. Ameren has not recorded a liability for these contingent obligations because it does not believe a payment with respect to any of these guarantees or letters of credit was probable as of June 30, 2015.
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 Corporation from continuing operations for the three and six months ended June 30, 2015 and 2014, and total assets of continuing operations as of June 30, 2015, and December 31, 2014:
Three Months
Ameren
Missouri
 
Ameren
Illinois
 
Other
 
Intersegment
Eliminations
 
Ameren
 
2015
 
 
 
 
 
 
 
 
 
 
External revenues
$
872

 
$
512

 
$
17

  
$
—

 
$
1,401

 
Intersegment revenues
12

 
1

 
—

  
(13
)
 
—

 
Net income attributable to Ameren Corporation from continuing operations
61

 
31

 
6

 
—

 
98

 
2014
 
 
 
 
 
 
 
 
 
 
External revenues
$
893

 
$
518

 
$
8

 
$
—

 
$
1,419

 
Intersegment revenues
7

 
1

 
—

 
(8
)
 
—

 
Net income (loss) attributable to Ameren Corporation from continuing operations
126

 
28

 
(4
)
 
—

 
150

 
Six Months
  
 
  
 
  
 
  
 
  
 
2015
 
 
 
 
 
 
 
 
 
 
External revenues
$
1,665

 
$
1,256

 
$
36

 
$
—

 
$
2,957

 
Intersegment revenues
19

 
2

 
1

 
(22
)
 
—

 
Net income attributable to Ameren Corporation from continuing operations
102

 
84

 
20

 
—

 
206

 
2014
 
 
 
 
 
 
 
 
 
 
External revenues
$
1,704

 
$
1,292

 
$
17

 
$
—

 
$
3,013

 
Intersegment revenues
13

 
1

 
1

 
(15
)
 
—

 
Net income (loss) attributable to Ameren Corporation from continuing operations
173

 
81

 
(7
)
 
—

 
247

 
As of June 30, 2015:
 
 
 
 
 
 
 
 
 
 
Total assets
$
13,721

 
$
8,500

 
$
1,036

 
$
(120
)
 
$
23,137

(a) 
As of December 31, 2014:
 
 
 
 
 
 
 
 
 
 
Total assets
$
13,541

 
$
8,381

 
$
942

 
$
(203
)
 
$
22,661

(a) 
(a)    Excludes total assets from discontinued operations of $15 million as of June 30, 2015, and December 31, 2014.
Summary Of Significant Accounting Policies (Policies)
Consolidation 
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 presentation of our results. The preparation of financial statements in conformity with GAAP requires management to make certain estimates and assumptions. Such estimates and assumptions affect reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the dates of financial statements, and the reported amounts of revenues and expenses during the reported periods. Actual results could differ from those estimates. 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.
Uncertain Tax Positions 
It is reasonably possible that events will occur during the next 12 months that would cause the total amount of our unrecognized tax benefits to fluctuate. We do not believe any such fluctuations would be material to our results of operations, financial position, or liquidity.
State income tax returns are generally subject to examination for a period of three years after filing. We do not currently have material state income tax issues under examination, administrative appeal, or litigation. The state impact of any federal changes remains subject to examination by various states for a period of up to one year after formal notification to the states.
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 2014, FASB issued authoritative accounting guidance to clarify the principles for recognizing revenue and to develop a common revenue standard for GAAP. The guidance requires an entity to recognize an amount of revenue for the transfer of promised goods or services to customers that reflects the consideration which 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. In July 2015, FASB deferred the effective date of the new revenue standard to the first quarter of 2018. The guidance allows entities to choose one of two transition methods, either by applying the guidance retrospectively to each reporting period presented or by recording a cumulative effect adjustment to retained earnings in the period of initial adoption. The Ameren Companies are currently assessing the impacts of this guidance on their results of operations, financial positions and disclosures, as well as the transition method that they will use to adopt the guidance.
Presentation of Debt Issuance Costs
In April 2015, FASB issued authoritative accounting guidance to simplify the presentation of debt issuance costs. The guidance requires debt issuance costs to be presented in the balance sheet as a reduction to the associated debt liability. Currently, debt issuance costs are presented as a component of “Other assets” on the Ameren Companies’ balance sheets. As of June 30, 2015, Ameren, Ameren Missouri, and Ameren Illinois had debt issuance costs of $36 million, $20 million, and $16 million, respectively. The guidance will be effective for the Ameren Companies in the first quarter of 2016 and applied retrospectively, and it will not affect the Ameren Companies' results of operations or cash flows.
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.
Retirement Benefits Retirement Benefits (Policies)
Retirement Benefits
Ameren’s pension plans are funded in compliance with income tax regulations and to meet federal funding or regulatory requirements. As a result, Ameren expects to fund its pension plans at a level equal to the greater of the pension expense or the legally required minimum contribution. Considering Ameren’s assumptions at June 30, 2015, the plan’s estimated investment performance through June 30, 2015, and Ameren’s pension funding policy, Ameren expects to make annual contributions of $25 million to $115 million through 2019, with aggregate estimated contributions of $290 million. These amounts are estimates which may change with actual investment performance, changes in interest rates, any pertinent changes in government regulations, and any voluntary contributions. Separately, our policy for postretirement benefits is primarily to fund the voluntary employees’ beneficiary association trusts to match the annual postretirement expense.
Summary Of Significant Accounting Policies (Tables)
Schedule of Change in Asset Retirement Obligation 
The following table provides a reconciliation of the beginning and ending carrying amount of AROs for the six months ended June 30, 2015:
 
Ameren
Missouri
 
Ameren
Illinois(a)
 
Ameren
 
Balance at December 31, 2014
$
389

 
$
7

 
$
396

 
Accretion in 2015(b)
11

 
(c)

 
11

 
Change in estimates(d)
182

 
(c)

 
182

 
Balance at June 30, 2015
$
582

 
$
7

 
$
589

 
(a)
Included in “Other deferred credits and liabilities” on the balance sheet.
(b)
Accretion expense was recorded as an increase to regulatory assets.
(c)
Less than $1 million.
(d)
The ARO increase resulted in a corresponding increase recorded to “Property and Plant, Net.” During the first quarter of 2015, Ameren and Ameren Missouri increased their AROs related to the decommissioning of the Callaway energy center by $99 million to reflect the 2015 cost study and funding analysis filed with the MoPSC, extension of the estimated operating life until 2044, and a reduction in the discount rate assumption. See Note 10 - Callaway Energy Center for additional information. In addition, during the second quarter of 2015, as a result of new federal regulations, Ameren and Ameren Missouri recorded an increase of $79 million to their AROs associated with CCR storage facilities. See Note 9 - Commitments and Contingencies for additional information. Also during the second quarter of 2015, Ameren and Ameren Missouri increased their AROs by $4 million due to a change in the estimated retirement dates of the Meramec and Rush Island energy centers as a result of the MoPSC’s April 2015 electric rate order.
Summary Of Nonvested Shares Related To Long-Term Incentive Plan 
A summary of nonvested performance share units at June 30, 2015, and changes during the six months ended June 30, 2015, under the 2006 Incentive Plan and the 2014 Incentive Plan are presented below:
 
Number of Performance Share Units
Weighted-average Fair Value Per Performance Share Unit
Nonvested at January 1, 2015
1,162,377

$
35.35

Granted(a)
567,240

52.88

Forfeitures
(1,944
)
34.75

Vested(b)
(85,694
)
46.79

Nonvested at June 30, 2015
1,641,979

$
40.81

(a)
Performance share units granted to certain executive and nonexecutive officers and other eligible employees in 2015 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 Unrecognized Tax Benefits 
The following table presents the total amount of reserves for unrecognized tax benefits (detriments) related to uncertain tax positions as of June 30, 2015, and December 31, 2014:
 
June 30, 2015
 
December 31, 2014
Ameren
$
—

 
$
54

Ameren Missouri
—

 
—

Ameren Illinois
—

 
(1
)
Schedule of Unrecognized Tax Benefits That Would Impact Effective Tax Rate 
The following table presents the amount of reserves for unrecognized tax benefits, included in the table above, related to uncertain tax positions that, if recognized, would have impacted results of operations as of December 31, 2014:
 
 
 
December 31, 2014
Ameren

 
$
52

Ameren Missouri

 
—

Ameren Illinois

 
(1
)
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 six months ended June 30, 2015 and 2014:
 
Three Months
 
Six Months
 
2015
 
2014
 
2015
 
2014
Ameren Missouri
$
41

 
$
39

 
$
75

 
$
73

Ameren Illinois
10

 
11

 
33

 
37

Ameren
$
51

 
$
50

 
$
108

 
$
110

Short-Term Debt And Liquidity Short-Term Debt and Liquidity (Tables)
Schedule of Short-term Debt
The following table presents commercial paper outstanding at Ameren (parent), Ameren Missouri, and Ameren Illinois as of June 30, 2015, and December 31, 2014:
  
June 30, 2015
 
December 31, 2014
Ameren (parent)
$
836

 
$
585

Ameren Missouri
38

 
97

Ameren Illinois
12

 
32

Ameren Consolidated
$
886

 
$
714

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 six months ended June 30, 2015 and 2014:
 
 
Ameren
(parent)
Ameren
Missouri
Ameren
Illinois
Ameren Consolidated
2015
 
 
 
 
 
 
Average daily commercial paper outstanding
 
$
754

 
$
84

$
5

$
843

Weighted-average interest rate
 
0.57
%
 
0.50
%
0.44
%
0.56
%
Peak commercial paper during period(a)
 
$
849

 
$
294

$
39

$
1,108

Peak interest rate
 
0.70
%
 
0.60
%
0.60
%
0.70
%
2014
 
 
 
 
 
 
Average daily commercial paper outstanding
 
$
328

 
$
146

$
242

$
607

Weighted-average interest rate
 
0.32
%
 
0.31
%
0.32
%
0.32
%
Peak commercial paper during period(a)
 
$
503

 
$
495

$
300

$
907

Peak interest rate
 
0.35
%
 
0.70
%
0.34
%
0.70
%

(a)
The timing of peak commercial paper issuances varies by company, and therefore the peak amounts presented by company might not equal the Ameren Consolidated peak commercial paper issuances for the period.
Long-Term Debt And Equity Financings (Tables)
Schedule Of 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 bonds or preferred stock. The following table summarizes the required and actual interest coverage ratios, and dividend coverage ratios, and bonds and preferred stock issuable as of June 30, 2015, 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
 
3.5
$
3,305
 
≥2.5
 
94.4
$
2,095
 
Ameren Illinois
 
≥2.0
 
6.7
 
3,533
(d) 
≥1.5
 
2.8
 
203
(e) 
(a)
Coverage required on the annual interest charges on first mortgage bonds outstanding and to be issued. Coverage is not required in certain cases when additional first mortgage bonds are issued on the basis of retired bonds.
(b)
Amount of bonds issuable based either on required coverage ratios or unfunded property additions, whichever is more restrictive. The amounts shown also include bonds issuable based on retired bond capacity of $946 million and $204 million at Ameren Missouri and Ameren Illinois, respectively.
(c)
Coverage required on the annual dividend on preferred stock outstanding and to be issued, as required in the respective company’s articles of incorporation.
(d)
Amount of bonds issuable by Ameren Illinois based on unfunded property additions and retired bonds solely under the former IP mortgage indenture. The amount of bonds issuable by Ameren Illinois is also subject to the lien restrictions contained in the 2012 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 six months ended June 30, 2015 and 2014:
 
Three Months
 
Six Months
 
 
2015
 
2014
 
2015
 
2014
 
Ameren:(a)
 
 
 
 
 
 
 
 
Miscellaneous income:
 
 
 
 
 
 
 
 
Allowance for equity funds used during construction
$
6

 
$
9

 
$
11

 
$
16

 
Interest income on industrial development revenue bonds
6

 
7

 
13

 
14

 
Interest income
4

 
2

 
8

 
5

 
Other
—

 
3

 
3

 
4

 
Total miscellaneous income
$
16

 
$
21

 
$
35

 
$
39

 
Miscellaneous expense:
 
 
 
 
 
 
 
 
Donations
$
2

 
$
1

 
$
10

 
$
6

 
Other
4

 
3

 
7

 
7

 
Total miscellaneous expense
$
6

 
$
4

 
$
17

 
$
13

 
Ameren Missouri:
 
 
 
 
 
 
 
 
Miscellaneous income:
 
 
 
 
 
 
 
 
Allowance for equity funds used during construction
$
5

 
$
8

 
$
9

 
$
15

 
Interest income on industrial development revenue bonds
6

 
7

 
13

 
14

 
Interest income
1

 
1

 
1

 
1

 
Total miscellaneous income
$
12

 
$
16

 
$
23

 
$
30

 
Miscellaneous expense:
 
 
 
 
 
 
 
 
Donations
$
1

 
$
1

 
$
3

 
$
3

 
Other
1

 
1

 
2

 
3

 
Total miscellaneous expense
$
2

 
$
2

 
$
5

 
$
6

 
Ameren Illinois:
 
 
 
 
 
 
 
 
Miscellaneous income:
 
 
 
 
 
 
 
 
Allowance for equity funds used during construction
$
1

 
$
1

 
$
2

 
$
1

 
Interest income
3

 
1

 
7

 
3

 
Other
—

 
3

 
2

 
4

 
Total miscellaneous income
$
4

 
$
5

 
$
11

 
$
8

 
Miscellaneous expense:
 
 
 
 
 
 
 
 
Donations
$
1

 
$
—

 
$
4

 
$
3

 
Other
1

 
1

 
3

 
2

 
Total miscellaneous expense
$
2

 
$
1

 
$
7

 
$
5

 
(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 June 30, 2015, and December 31, 2014. As of June 30, 2015, these contracts ran through October 2017, March 2021, May 2032, and December 2016 for fuel oils, natural gas, power, and uranium, respectively.
  
Quantity (in millions, except as indicated)
 
2015
2014
Commodity
Ameren Missouri
Ameren Illinois
Ameren
Ameren Missouri
Ameren Illinois
Ameren
Fuel oils (in gallons)(a)
39

(b)

39

50

(b)

50

Natural gas (in mmbtu)
29

127

156

28

108

136

Power (in megawatthours)
1

10

11

1

11

12

Uranium (pounds in thousands)
316

(b)

316

332

(b)

332

(a)
Fuel oils consist of heating oil and ultra-low-sulfur diesel.
(b)
Not applicable.
Derivative Instruments Carrying Value 
The following table presents the carrying value and balance sheet location of all derivative instruments, none of which were designated as hedging instruments, as of June 30, 2015, and December 31, 2014:
 
Balance Sheet Location
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
2015
 
 
 
 
 
 
Fuel oils
Other current assets
 
$
1

 
$
—

 
$
1

Natural gas
Other assets
 
—

 
1

 
1

Power
Other current assets
 
29

 
—

 
29

 
Total assets
 
$
30

 
$
1

 
$
31

Fuel oils
Other current liabilities
 
$
14

 
$
—

 
$
14

 
Other deferred credits and liabilities
 
5

 
—

 
5

Natural gas
MTM derivative liabilities
 
(a)

 
24

 
(a)

 
Other current liabilities
 
4

 
—

 
28

 
Other deferred credits and liabilities
 
7

 
14

 
21

Power
MTM derivative liabilities
 
(a)

 
11

 
(a)

 
Other current liabilities
 
2

 
—

 
13

 
Other deferred credits and liabilities
 
—

 
154

 
154

Uranium
Other current liabilities
 
2

 
—

 
2

 
Total liabilities
 
$
34

 
$
203

 
$
237

2014
 
 
 
 
 
 
Fuel oils
Other current assets
 
$
2

 
$
—

 
$
2

Natural gas
Other current assets
 
1

 
1

 
2

Power
Other current assets
 
15

 
—

 
15

 
Total assets
 
$
18

 
$
1

 
$
19

Fuel oils
Other current liabilities
 
$
22

 
$
—

 
$
22

 
Other deferred credits and liabilities
 
7

 
—

 
7

Natural gas
MTM derivative liabilities
 
(a)

 
31

 
(a)

 
Other current liabilities
 
6

 
—

 
37

 
Other deferred credits and liabilities
 
6

 
13

 
19

Power
MTM derivative liabilities
 
(a)

 
11

 
(a)

 
Other current liabilities
 
3

 
—

 
14

 
Other deferred credits and liabilities
 
—

 
131

 
131

Uranium
Other current liabilities
 
2

 
—

 
2

 
Total liabilities
 
$
46

 
$
186

 
$
232


(a)
Balance sheet line item not applicable to registrant.
Cumulative Pretax Net Gains (Losses) On All Derivative Instruments In OCI 
The following table presents the cumulative amount of pretax net gains (losses) on all derivative instruments deferred in regulatory assets or regulatory liabilities as of June 30, 2015, and December 31, 2014:
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
2015
 
 
 
 
 
Fuel oils derivative contracts(a)
$
(19
)
 
$
—

 
$
(19
)
Natural gas derivative contracts(b)
(11
)
 
(37
)
 
(48
)
Power derivative contracts(c)
27

 
(165
)
 
(138
)
Uranium derivative contracts(d)
(2
)
 
—

 
(2
)
2014
 
 
 
 
 
Fuel oils derivative contracts
$
(29
)
 
$
—

 
$
(29
)
Natural gas derivative contracts
(11
)
 
(43
)
 
(54
)
Power derivative contracts
12

 
(142
)
 
(130
)
Uranium derivative contracts
(2
)
 
—

 
(2
)
(a)
Represents net losses associated with fuel oils derivative contracts at Ameren Missouri. These contracts are a partial hedge of Ameren Missouri’s rail transportation surcharges for coal through December 2017. Current gains deferred as regulatory liabilities include $1 million at Ameren and Ameren Missouri. Current losses deferred as regulatory assets include $14 million at Ameren and Ameren Missouri.
(b)
Represents net losses associated with natural gas derivative contracts. These contracts are a partial hedge of natural gas requirements through March 2021 at Ameren and Ameren Missouri and through October 2018 at Ameren Illinois. Current losses deferred as regulatory assets include $28 million, $4 million, and $24 million at Ameren, Ameren Missouri, and Ameren Illinois, respectively.
(c)
Represents net gains (losses) associated with power derivative contracts. These contracts are a partial hedge of power price requirements through May 2032 at Ameren and Ameren Illinois and through December 2016 at Ameren Missouri. Current gains deferred as regulatory liabilities include $29 million at Ameren and Ameren Missouri. Current losses deferred as regulatory assets include $13 million, $2 million, and $11 million at Ameren, Ameren Missouri, and Ameren Illinois, respectively.
(d)
Represents net losses on uranium derivative contracts at Ameren Missouri. These contracts are a partial hedge of Ameren Missouri’s uranium requirements through January 2017. Current losses deferred as regulatory assets include $2 million at Ameren and Ameren Missouri.
Der
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 June 30, 2015, and December 31, 2014:
 
 
 
 
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
2015
 
 
 
 
 
 
 
 
Assets:
 
 
 
 
 
 
 
 
Ameren Missouri
 
$
30

 
$
3

 
$
—

 
$
27

Ameren Illinois
 
1

 
—

 
—

 
1

Ameren
 
$
31

 
$
3

 
$
—

 
$
28

Liabilities:
 
 
 
 
 
 
 
 
Ameren Missouri
 
$
34

 
$
3

 
$
2

 
$
29

Ameren Illinois
 
203

 
—

 
—

 
203

Ameren
 
$
237

 
$
3

 
$
2

 
$
232

2014
 
 
 
 
 
 
 
 
Assets:
 
 
 
 
 
 
 
 
Ameren Missouri
 
$
18

 
$
5

 
$
—

 
$
13

Ameren Illinois
 
1

 
—

 
—

 
1

Ameren
 
$
19

 
$
5

 
$
—

 
$
14

Liabilities:
 
 
 
 
 
 
 
 
Ameren Missouri
 
$
46

 
$
5

 
$
5

 
$
36

Ameren Illinois
 
186

 
—

 
—

 
186

Ameren
 
$
232

 
$
5

 
$
5

 
$
222

(a)
Cash collateral received reduces gross asset balances and is included in “Other current liabilities” and “Other deferred credits and liabilities” on the balance sheet. Cash collateral posted reduces gross liability balances and is included in “Other current assets” and “Other assets” on the balance sheet.
Derivative Instruments With Credit Risk-Related Contingent Features 
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 June 30, 2015, and (2) those counterparties with rights to do so requested collateral.
 
Aggregate Fair Value of
Derivative Liabilities(a)
 
Cash
Collateral Posted
 
Potential Aggregate Amount of
Additional Collateral Required(b)
2015
 
 
 
 
 
Ameren Missouri
$
80

 
$
3

 
$
73

Ameren Illinois
77

 
—

 
72

Ameren
$
157

 
$
3

 
$
145

(a)
Prior to 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 for the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy as of June 30, 2015:
 
 
Fair Value
 
 
 
Weighted Average
 
 
Assets
Liabilities
Valuation Technique(s)
Unobservable Input
Range
Level 3 Derivative asset and liability - commodity contracts(a):
 
 
 
Ameren
Fuel oils
$
1

$
(2
)
Option model
Volatilities(%)(b)
32 - 50
37
 
 
 
 
Discounted cash flow
Ameren Missouri credit risk(%)(b)(c)
0.40
(d)
 
Natural gas
—

(1
)
Discounted cash flow
Nodal basis($/mmbtu)(e)
(0.60) - 0
(0.40)
 
 
 
 
 
Counterparty credit risk(%)(b)(c)
0.21 - 2.01
0.83
 
 
 
 
 
Ameren Illinois credit risk(%)(b)(c)
0.40
(d)
 
Power(f)
29

(167
)
Discounted cash flow
Average forward peak and off-peak pricing - forwards/swaps($/MWh)(g)
26 - 45
31
 
 
 
 
 
Estimated auction price for FTRs($/MW)(e)
(1,006) - 1,606
184
 
 
 
 
 
Nodal basis($/MWh)(e)
(11) - (1)
(3)
 
 
 
 
 
Counterparty credit risk(%)(b)(c)
0.39 - 13.86
8.64
 
 
 
 
 
Ameren Missouri and Ameren Illinois credit risk(%)(b)(c)
0.40
(d)
 
 
 
 
Fundamental energy production model
Estimated future gas prices($/mmbtu)(e)
3 - 6
4
 
 
 
 
 
Escalation rate(%)(e)(h)
2
(d)
 
 
 
 
Contract price allocation
Estimated renewable energy credit costs($/credit)(e)
5 - 7
6
 
Uranium
—

(2
)
Discounted cash flow
Average forward uranium pricing($/pound)(e)
36 - 39
37
Ameren Missouri
Fuel oils
$
1

$
(2
)
Option model
Volatilities(%)(b)
32 - 50
37
 
 
 
 
Discounted cash flow
Ameren Missouri credit risk(%)(b)(c)
0.40
(d)
 
Power(f)
29

(2
)
Discounted cash flow
Average forward peak and off-peak pricing - forwards/swaps($/MWh)(b)
26 - 45
34
 
 
 
 
 
Estimated auction price for FTRs($/MW)(e)
(1,006) - 1,606
184
 
 
 
 
 
Nodal basis($/MWh)(b)
(11) - (4)
(9)
 
 
 
 
 
Counterparty credit risk(%)(b)(c)
0.39 - 13.86
8.64
 
Uranium
—

(2
)
Discounted cash flow
Average forward uranium pricing($/pound)(e)
36 - 39
37
Ameren Illinois
Natural gas
$
—

$
(1
)
Discounted cash flow
Nodal basis($/mmbtu)(e)
(0.60) - 0
(0.40)
 
 
 
 
 
Counterparty credit risk(%)(b)(c)
0.21 - 2.01
0.83
 
 
 
 
 
Ameren Illinois credit risk(%)(b)(c)
0.40
(d)
 
Power(f)
—

(165
)
Discounted cash flow
Average forward peak and off-peak pricing - forwards/swaps($/MWh)(e)
27 - 37
30
 
 
 
 
 
Nodal basis($/MWh)(e)
(6) - (1)
(3)
 
 
 
 
 
Ameren Illinois credit risk(%)(b)(c)
0.40
(d)
 
 
 
 
Fundamental energy production model
Estimated future gas prices($/mmbtu)(e)
3 - 6
4
 
 
 
 
 
Escalation rate(%)(e)(h)
2
(d)
 
 
 
 
Contract price allocation
Estimated renewable energy credit costs($/credit)(e)
5 - 7
6

(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 lower (higher) fair value measurement.
(c)
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.
(d)
Not applicable.
(e)
Generally, significant increases (decreases) in this input in isolation would result in a significantly higher (lower) fair value measurement.
(f)
Power valuations use visible third-party pricing evaluated by month for peak and off-peak demand through 2019. Valuations beyond 2019 use fundamentally modeled pricing by month for peak and off-peak demand.
(g)
The balance at Ameren is comprised of Ameren Missouri and Ameren Illinois power contracts, which respond differently to unobservable input changes due to their opposing positions. As such, refer to the power sensitivity analysis for each company above.
(h)
Escalation rate applies to power prices 2026 and beyond.
The following table describes the valuation techniques and unobservable inputs for the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy as of December 31, 2014:
 
 
Fair Value
 
 
 
 
Weighted
 
 
Assets
Liabilities
 
Valuation Technique(s)
Unobservable Input
Range
Average
Level 3 Derivative asset and liability – commodity contracts(a):
 
 
 
Ameren
Fuel oils
$
2

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

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

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

(2
)
 
Discounted cash flow
Average forward uranium pricing($/pound)(e)
35 - 40
36
Ameren Missouri
Fuel oils
$
2

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

(1
)
 
Option model
Volatilities(%)(b)
31 - 144
53
 
 
 
 
 
 
Nodal basis($/mmbtu)(e)
(0.40) - 0
(0.30)
 
 
 
 
 
Discounted cash flow
Nodal basis($/mmbtu)(e)
(0.10)
(d)
 
 
 
 
 
 
Counterparty credit risk(%)(b)(c)
0.57 - 13
5
 
 
 
 
 
 
Ameren Missouri credit risk(%)(b)(c)
0.43
(d)
 
Power(g)
11

(2
)
 
Discounted cash flow
Average forward peak and off-peak pricing – forwards/swaps($/MWh)(b)
27 - 50
32
 
 
 
 
 
 
Estimated auction price for FTRs($/MW)(e)
(1,833) - 2,743
171
 
 
 
 
 
 
Counterparty credit risk(%)(b)(c)
0.26
(d)
 
 
 
 
 
 
Ameren Missouri credit risk(%)(b)(c)
0.43
(d)
 
Uranium
—

(2
)
 
Discounted cash flow
Average forward uranium pricing($/pound)(e)
35 - 40
36
Ameren Illinois
Natural Gas
$
1

$
(1
)
 
Option model
Volatilities(%)(b)
50 - 144
94
 
 
 
 
 
 
Nodal basis($/mmbtu)(e)
(0.10) - 0
(0.10)
 
 
 
 
 
Discounted cash flow
Nodal basis($/mmbtu)(e)
(0.40) - 0.10
(0.20)
 
 
 
 
 
 
Counterparty credit risk(%)(b)(c)
0.43 - 2
0.83
 
 
 
 
 
 
Ameren Illinois credit risk(%)(b)(c)
0.43
(d)
 
Power(g)
—

(142
)
 
Discounted cash flow
Average forward peak and off-peak pricing – forwards/swaps($/MWh)(e)
27 - 38
32
 
 
 
 
 
 
Nodal basis($/MWh)(e)
(6) - 0
(2)
 
 
 
 
 
 
Ameren Illinois credit risk(%)(b)(c)
0.43
(d)
 
 
 
 
 
Fundamental energy production model
Estimated future gas prices($/mmbtu)(e)
4 - 5
4
 
 
 
 
 
 
Escalation rate(%)(e)(i)
0 - 1
1
 
 
 
 
 
Contract price allocation
Estimated renewable energy credit costs($/credit)(e)
5 - 7
6

(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 lower (higher) fair value measurement.
(c)
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.
(d)
Not applicable.
(e)
Generally, significant increases (decreases) in this input in isolation would result in a significantly higher (lower) fair value measurement.
(f)
Escalation rate applies to fuel oil prices 2017 and beyond.
(g)
Power valuations use visible third-party pricing evaluated by month for peak and off-peak demand through 2018. Valuations beyond 2018 use fundamentally modeled pricing by month for peak and off-peak demand.
(h)
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. As such, refer to the power sensitivity analysis for each company above.
(i)
Escalation rate applies to power prices 2026 and beyond.
Schedule Of Fair Value Hierarchy Of Assets And Liabilities Measured At Fair Value On Recurring Basis 
The following table sets forth, by level within the fair value hierarchy, our assets and liabilities measured at fair value on a recurring basis as of June 30, 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):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
—

 
$
—

 
$
1

 
$
1

 
 
Natural gas
 
—

 
1

 
—

 
1

 
 
Power
 
—

 
—

 
29

 
29

 
 
Total derivative assets - commodity contracts
 
$
—

 
$
1

 
$
30

 
$
31

 
 
Nuclear decommissioning trust fund:
 
 
 
 
 
 
 
 
 
 
Cash and cash equivalents
 
$
6

 
$
—

 
$
—

 
$
6

 
 
Equity securities:
 
 
 
 
 
 
 
 
 
 
U.S. large capitalization
 
370

 
—

 
—

 
370

 
 
Debt securities:
 
 
 
 
 
 
 
 
 
 
Corporate bonds
 
—

 
59

 
—

 
59

 
 
U.S. treasury and agency securities
 
—

 
100

 
—

 
100

 
 
Other
 
—

 
22

 
—

 
22

 
 
Total nuclear decommissioning trust fund
 
$
376

 
$
181

 
$
—

 
$
557

(b) 
 
Total Ameren
 
$
376

 
$
182

 
$
30

 
$
588

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

 
$
—

 
$
1

 
$
1

 
 
Power
 
—

 
—

 
29

 
29

 
 
Total derivative assets - commodity contracts
 
$
—

 
$
—

 
$
30

 
$
30

 
 
Nuclear decommissioning trust fund:
 
 
 
 
 
 
 
 
 
 
Cash and cash equivalents
 
$
6

 
$
—

 
$
—

 
$
6

 
 
Equity securities:
 
 
 
 
 
 
 
 
 
 
U.S. large capitalization
 
370

 
—

 
—

 
370

 
 
Debt securities:
 
 
 
 
 
 
 
 
 
 
Corporate bonds
 
—

 
59

 
—

 
59

 
 
U.S. treasury and agency securities
 
—

 
100

 
—

 
100

 
 
Other
 
—

 
22

 
—

 
22

 
 
Total nuclear decommissioning trust fund
 
$
376

 
$
181

 
$
—

 
$
557

(b) 
 
Total Ameren Missouri
 
$
376

 
$
181

 
$
30

 
$
587

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

 
$
1

 
$
—

 
$
1

 
Liabilities:
 
 
 
 
 
 
 
 
 
 
Ameren
Derivative liabilities - commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
17

 
$
—

 
$
2

 
$
19

 
 
Natural gas
 
—

 
48

 
1

 
49

 
 
Power
 
—

 
—

 
167

 
167

 
 
Uranium
 
—

 
—

 
2

 
2

 
 
Total Ameren
 
$
17

 
$
48

 
$
172

 
$
237

 
Ameren
Derivative liabilities - commodity contracts(a):
 
 
 
 
 
 
 
 
 
Missouri
Fuel oils
 
$
17

 
$
—

 
$
2

 
$
19

 
 
Natural gas
 
—

 
11

 
—

 
11

 
 
Power
 
—

 
—

 
2

 
2

 
 
Uranium
 
—

 
—

 
2

 
2

 
 
Total Ameren Missouri
 
$
17

 
$
11

 
$
6

 
$
34

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

 
$
37

 
$
1

 
$
38

 
 
Power
 
—

 
—

 
165

 
165

 
 
Total Ameren Illinois
 
$
—

 
$
37

 
$
166

 
$
203

 
(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, 2014:
 
 
 
Quoted Prices in
Active Markets for
Identical Assets
or Liabilities
(Level 1)
 
Significant Other
Observable Inputs
(Level 2)
 
Significant Other
Unobservable
Inputs
(Level 3)
 
Total
 
Assets:
 
 
 
 
 
 
 
 
 
 
Ameren
Derivative assets - commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
—

 
$
—

 
$
2

 
$
2

 
 
Natural gas
 
—

 
1

 
1

 
2

 
 
Power
 
—

 
4

 
11

 
15

 
 
Total derivative assets - commodity contracts
 
$
—

 
$
5

 
$
14

 
$
19

 
 
Nuclear decommissioning trust fund:
 
 
 
 
 
 
 
 
 
 
Cash and cash equivalents
 
$
1

 
$
—

 
$
—

 
$
1

 
 
Equity securities:
 
 
 
 
 
 
 
 
 
 
U.S. large capitalization
 
364

 
—

 
—

 
364

 
 
Debt securities:
 
 
 
 
 
 
 
 
 
 
Corporate bonds
 
—

 
63

 
—

 
63

 
 
U.S. treasury and agency securities
 
—

 
102

 
—

 
102

 
 
Other
 
—

 
17

 
—

 
17

 
 
Total nuclear decommissioning trust fund
 
$
365

 
$
182

 
$
—

 
$
547

(b) 
 
Total Ameren
 
$
365

 
$
187

 
$
14

 
$
566

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

 
$
—

 
$
2

 
$
2

 
 
Natural gas
 
—

 
1

 
—

 
1

 
 
Power
 
—

 
4

 
11

 
15

 
 
Total derivative assets - commodity contracts
 
$
—

 
$
5

 
$
13

 
$
18

 
 
Nuclear decommissioning trust fund:
 
 
 
 
 
 
 
 
 
 
Cash and cash equivalents
 
$
1

 
$
—

 
$
—

 
$
1

 
 
Equity securities:
 
 
 
 
 
 
 
 
 
 
U.S. large capitalization
 
364

 
—

 
—

 
364

 
 
Debt securities:
 
 
 
 
 
 
 
 
 
 
Corporate bonds
 
—

 
63

 
—

 
63

 
 
U.S. treasury and agency securities
 
—

 
102

 
—

 
102

 
 
Other
 
—

 
17

 
—

 
17

 
 
Total nuclear decommissioning trust fund
 
$
365

 
$
182

 
$
—

 
$
547

(b) 
 
Total Ameren Missouri
 
$
365

 
$
187

 
$
13

 
$
565

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

 
$
—

 
$
1

 
$
1

 
Liabilities:
 
 
 
 
 
 
 
 
 
 
Ameren
Derivative liabilities - commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
21

 
$
—

 
$
8

 
$
29

 
 
Natural gas
 
1

 
53

 
2

 
56

 
 
Power
 
—

 
1

 
144

 
145

 
 
Uranium
 
—

 
—

 
2

 
2

 
 
Total Ameren
 
$
22

 
$
54

 
$
156

 
$
232

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

 
$
—

 
$
8

 
$
29

 
 
Natural gas
 
1

 
10

 
1

 
12

 
 
Power
 
—

 
1

 
2

 
3

 
 
Uranium
 
—

 
—

 
2

 
2

 
 
Total Ameren Missouri
 
$
22

 
$
11

 
$
13

 
$
46

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

 
$
43

 
$
1

 
$
44

 
 
Power
 
—

 
—

 
142

 
142

 
 
Total Ameren Illinois
 
$
—

 
$
43

 
$
143

 
$
186

 
(a)
The derivative asset and liability balances are presented net of counterparty credit considerations.
(b)
Balance excludes $2 million of receivables, payables, and accrued income, net.
Schedule Of Changes In The Fair Value Of Financial Assets And Liabilities Classified As Level Three In The Fair Value Hierarchy 
The following table summarizes the changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the three months ended June 30, 2015:
  
 
Net derivative commodity contracts
 
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
Fuel oils:
 
 
 
 
 
 
Beginning balance at April 1, 2015
$
(6
)
$
(a)

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

 
(a)

 
1

Settlements
 
2

 
(a)

 
2

Transfers out of Level 3
 
2

 
(a)

 
2

Ending balance at June 30, 2015
$
(1
)
$
(a)

$
(1
)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2015
$
3

$
(a)

$
3

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

$
—

Purchases
 
—

 
(1
)
 
(1
)
Settlements
 
1

 
(1
)
 
—

Ending balance at June 30, 2015
$
—

$
(1
)
$
(1
)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2015
$
—

$
—

$
—

Power:
 
 
 
 
 
 
Beginning balance at April 1, 2015
$
4

$
(164
)
$
(160
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities
 
—

 
(4
)
 
(4
)
Purchases
 
29

 
—

 
29

Settlements
 
(6
)
 
3

 
(3
)
Ending balance at June 30, 2015
$
27

$
(165
)
$
(138
)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2015
$
1

$
(5
)
$
(4
)
Uranium:
 
 
 
 
 
 
Beginning balance at April 1, 2015
$
(1
)
$
(a)

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

 
(1
)
Ending balance at June 30, 2015
$
(2
)
$
(a)

$
(2
)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2015
$
(1
)
$
(a)

$
(1
)
(a)
Not applicable.

The following table summarizes the changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the three months ended June 30, 2014:
 
 
Net derivative commodity contracts
 
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
Fuel oils:
 
 
 
 
 
 
Beginning balance at April 1, 2014
$
1

$
(a)

$
1

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

 
(a)

 
1

Ending balance at June 30, 2014
$
2

$
(a)

$
2

Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2014
$
1

$
(a)

$
1

Natural gas:
 
 
 
 
 
 
Beginning balance at April 1, 2014
$
—

$
—

$
—

Purchases
 
—

 
1

 
1

Settlements
 
—

 
(1
)
 
(1
)
Ending balance at June 30, 2014
$
—

$
—

$
—

Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2014
$
—

$
—

$
—

Power:
 
 
 
 
 
 
Beginning balance at April 1, 2014
$
10

$
(120
)
$
(110
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities
 
(13
)
 
16

 
3

Purchases
 
34

 
—

 
34

Settlements
 
(15
)
 
1

 
(14
)
Transfers out of Level 3
 
(1
)
 
—

 
(1
)
Ending balance at June 30, 2014
$
15

$
(103
)
$
(88
)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2014
$
(1
)
$
15

$
14

Uranium:
 
 
 
 
 
 
Beginning balance at April 1, 2014
$
(5
)
$
(a)

$
(5
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities
 
(4
)
 
(a)

 
(4
)
Settlements
 
2

 
(a)

 
2

Ending balance at June 30, 2014
$
(7
)
$
(a)

$
(7
)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2014
$
(4
)
$
(a)

$
(4
)
(a)
Not applicable.

The following table summarizes the changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the six months ended June 30, 2015:
  
 
Net derivative commodity contracts
 
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
Fuel oils:
 
 
 
 
 
 
Beginning balance at January 1, 2015
$
(6
)
$
(a)

$
(6
)
Settlements
 
3

 
(a)

 
3

Transfers out of Level 3
 
2

 
(a)

 
2

Ending balance at June 30, 2015
$
(1
)
$
(a)

$
(1
)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2015
$
—

$
(a)

$
—

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

$
(1
)
Settlements
 
1

 
(1
)
 
—

Ending balance at June 30, 2015
$
—

$
(1
)
$
(1
)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2015
$
—

$
—

$
—

Power:
 
 
 
 
 
 
Beginning balance at January 1, 2015
$
9

$
(142
)
$
(133
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities
 
(2
)
 
(29
)
 
(31
)
Purchases
 
29

 
—

 
29

Settlements
 
(9
)
 
6

 
(3
)
Ending balance at June 30, 2015
$
27

$
(165
)
$
(138
)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2015
$
—

$
(29
)
$
(29
)
Uranium:
 
 
 
 
 
 
Beginning balance at January 1, 2015
$
(2
)
$
(a)

$
(2
)
Ending balance at June 30, 2015
$
(2
)
$
(a)

$
(2
)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2015
$
—

$
(a)

$
—

(a)
Not applicable.

The following table summarizes the changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the six months ended June 30, 2014:
  
 
Net derivative commodity contracts
 
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
Fuel oils:
 
 
 
 
 
 
Beginning balance at January 1, 2014
$
5

$
(a)

$
5

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

 
(1
)
Settlements
 
(2
)
 
(a)

 
(2
)
Ending balance at June 30, 2014
$
2

$
(a)

$
2

Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2014
$
—

$
(a)

$
—

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

$
—

$
—

Purchases
 
—

 
(1
)
 
(1
)
Settlements
 
—

 
1

 
1

Ending balance at June 30, 2014
$
—

$
—

$
—

Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2014
$
—

$
—

$
—

Power:
 
 
 
 
 
 
Beginning balance at January 1, 2014
$
19

$
(108
)
$
(89
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities
 
(18
)
 
4

 
(14
)
Purchases
 
34

 
—

 
34

Settlements
 
(20
)
 
1

 
(19
)
Ending balance at June 30, 2014
$
15

$
(103
)
$
(88
)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2014
$
(3
)
$
1

$
(2
)
Uranium:
 
 
 
 
 
 
Beginning balance at January 1, 2014
$
(6
)
$
(a)

$
(6
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities
 
(4
)
 
(a)

 
(4
)
Settlements
 
3

 
(a)

 
3

Ending balance at June 30, 2014
$
(7
)
$
(a)

$
(7
)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2014
$
(4
)
$
(a)

$
(4
)
(a)
Not applicable.
Schedule Of Transfers Between Fair Value Hierarchy Levels 
The following table summarizes all transfers between fair value hierarchy levels related to derivative commodity contracts for the three and six months ended June 30, 2015, and 2014:
 
2015
2014
 
Ameren Missouri
Ameren Illinois
Ameren
Ameren Missouri
Ameren Illinois
Ameren
Three Months
 
 
 
 
 
 
Transfers out of Level 3 / Transfers into Level 1 - Fuel oils
$
2

$
—

$
2

$
—

$
—

$
—

Transfers out of Level 3 / Transfers into Level 2 - Power
—

—

—

(1
)
—

(1
)
Six Months
 
 
 
 
 
 
Transfers out of Level 3 / Transfers into Level 1 - Fuel oils
$
2

$
—

$
2

$
—

$
—

$
—

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 June 30, 2015, and December 31, 2014:
 
June 30, 2015
 
December 31, 2014
 
Carrying
Amount
 
Fair
Value
 
Carrying
Amount
 
Fair
Value
Ameren:(a)
 
 
 
 
 
 
 
Long-term debt and capital lease obligations (including current portion)
$
6,376

 
$
6,919

 
$
6,240

 
$
7,135

Preferred stock
142

 
122

 
142

 
122

Ameren Missouri:
 
 
 
 
 
 
 
Long-term debt and capital lease obligations (including current portion)
$
4,135

 
$
4,492

 
$
3,999

 
$
4,518

Preferred stock
80

 
73

 
80

 
73

Ameren Illinois:
 
 
 
 
 
 
 
Long-term debt
$
2,241

 
$
2,427

 
$
2,241

 
$
2,517

Preferred stock
62

 
49

 
62

 
49

(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 six months ended June 30, 2015 and 2014.
 
 
 
 
 
Three Months
 
Six Months
Agreement
Income Statement
Line Item
 
 
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
Missouri
 
Ameren
Illinois
Ameren Missouri power supply
Operating Revenues
 
2015
$
4

$
(a)

$
5

$
(a)

agreements with Ameren Illinois
 
 
2014
 
3

 
(a)

 
3

 
(a)

Ameren Missouri and Ameren Illinois
Operating Revenues
 
2015
 
7

 
1

 
13

 
2

rent and facility services
 
 
2014
 
4

 
1

 
9

 
1

Ameren Missouri and Ameren Illinois
Operating Revenues
 
2015
 
1

 
(b)

 
1

 
(b)

miscellaneous support services
 
 
2014
 
1

 
(b)

 
1

 
(b)

Total Operating Revenues
 
 
2015
$
12

$
1

$
19

$
2

 
 
 
2014
 
8

 
1

 
13

 
1

Ameren Illinois power supply
Purchased Power
 
2015
$
(a)

$
4

$
(a)

$
5

agreements with Ameren Missouri
 
 
2014
 
(a)

 
3

 
(a)

 
3

Ameren Illinois transmission
Purchased Power
 
2015
 
(a)

 
(b)

 
(a)

 
1

services with ATXI
 
 
2014
 
(a)

 
(b)

 
(a)

 
1

Total Purchased Power
 
 
2015
$
(a)

$
4

$
(a)

$
6

 
 
 
2014
 
(a)

 
3

 
(a)

 
4

Ameren Services support services
Other Operations and Maintenance
 
2015
$
32

$
30

$
66

$
59

agreement
 
 
2014
 
32

 
27

 
65

 
54

Money pool borrowings (advances)
Interest Charges/ Miscellaneous Income
 
2015
$
(b)

$
(b)

$
(b)

$
(b)

 
 
 
2014
 
(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 June 30, 2015. The property coverage and the nuclear liability coverage must be renewed on April 1 and January 1, respectively, of each year. Both coverages were renewed in 2015.
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) 
128

(b) 
 
$
13,361

(c) 
$
128

  
Property damage:
 
 
 
 
NEIL
$
2,750

(d) 
$
27

(e) 
European Mutual Association for Nuclear Insurance
500

(f) 
—

 
 
$
3,250

 
$
27

 
Replacement power:
 
 
 
 
NEIL
$
490

(g) 
$
10

(e) 
(a)
Provided through mandatory participation in an industrywide retrospective premium assessment program.
(b)
Retrospective premium under the Price-Anderson Act. This is subject to retrospective assessment with respect to a covered loss in excess of $375 million in the event of an incident at any licensed United States commercial reactor, payable at $19 million per year.
(c)
Limit of liability for each incident under the Price-Anderson liability provisions of the Atomic Energy Act of 1954, as amended. A company could be assessed up to $128 million per incident for each licensed reactor it operates with a maximum of $19 million per incident to be paid in a calendar year for each reactor. This limit is subject to change to account for the effects of inflation and changes in the number of licensed reactors.
(d)
NEIL provides $2.25 billion in property damage, decontamination, and premature decommissioning insurance for both radiation and nonradiation events. An additional $500 million is provided for radiation events only for a total of $2.75 billion.
(e)
All NEIL insured plants could be subject to assessments should losses exceed the accumulated funds from NEIL.
(f)
European Mutual Association for Nuclear Insurance provides $500 million in excess of the $2.75 billion and $2.25 billion property coverage for radiation and nonradiation events, respectively, provided by NEIL.
(g)
Provides replacement power cost insurance in the event of a prolonged accidental outage. Weekly indemnity up to $4.5 million for 52 weeks, which commences after the first twelve weeks of an outage, plus up to $3.6 million per week for a minimum of 71 weeks thereafter for a total not exceeding the policy limit of $490 million. Nonradiation events are sub-limited to $328 million.
Schedule of Asbestors-Related Litigation Pending Lawsuits 
The following table presents the pending asbestos-related lawsuits filed against the Ameren Companies as of June 30, 2015:
Ameren
 
Ameren
Missouri
 
Ameren
Illinois
 
Total(a)
1
 
28
 
36
 
49
(a)
Total does not equal the sum of the subsidiary unit lawsuits because some of the lawsuits name multiple Ameren entities as defendants.
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 six months ended June 30, 2015 and 2014:
  
Pension Benefits
 
Postretirement Benefits
 
 
Three Months
 
Six Months
 
Three Months
 
Six Months
 
  
2015
 
2014
 
2015
 
2014
 
2015
 
2014
 
2015
 
2014
 
Service cost
$
22

 
$
19

 
$
46

 
$
40

 
$
6

 
$
4

 
$
11

 
$
9

 
Interest cost
43

 
42

 
87

 
91

 
12

 
12

 
24

 
25

 
Expected return on plan assets
(62
)
 
(57
)
 
(124
)
 
(114
)
 
(17
)
 
(16
)
 
(34
)
 
(32
)
 
Amortization of:
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Prior service benefit
—

 
—

 
—

 
—

 
(1
)
 
(1
)
 
(2
)
 
(2
)
 
Actuarial loss (gain)
19

 
12

 
37

 
24

 
2

 
(2
)
 
3

 
(3
)
 
Settlement loss
1

 
—

 
1

 
—

 
—

 
—

 
—

 
—

 
Net periodic benefit cost (benefit)
$
23

 
$
16

 
$
47

 
$
41

 
$
2

 
$
(3
)
 
$
2

 
$
(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 six months ended June 30, 2015 and 2014:
  
Pension Benefits
 
Postretirement Benefits
 
 
Three Months
 
Six Months
 
Three Months
 
Six Months
 
  
2015
 
2014
 
2015
 
2014
 
2015
 
2014
 
2015
 
2014
 
Ameren Missouri
$
13

 
$
8

 
$
28

 
$
25

 
$
3

 
$
1

 
$
4

 
$
2

 
Ameren Illinois
10

 
7

 
19

 
15

 
(1
)
 
(3
)
 
(2
)
 
(4
)
 
Other
—

 
1

 
—

 
1

 
—

 
(1
)
 
—

 
(1
)
 
Ameren(a)
$
23

 
$
16

 
$
47

 
$
41

 
$
2

 
$
(3
)
 
$
2

 
$
(3
)
 

(a)
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 Statement, 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 six months ended June 30, 2015 and 2014:
 
Three Months
 
Six Months
 
2015
 
2014
 
2015
 
2014
Operating revenues
$
—

 
$
—

 
$
—

 
$
1

Operating benefits (expenses)
—

 
(1
)
 
3

 
(3
)
Operating income (loss) before income tax
—

 
(1
)
 
3

 
(2
)
Income tax benefit
52

 
—

 
49

 
—

Income (loss) from discontinued operations, net of taxes
$
52

 
$
(1
)
 
$
52

 
$
(2
)
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 June 30, 2015, and December 31, 2014:
 
June 30, 2015
 
December 31, 2014
Assets of discontinued operations
 
 
 
Accumulated deferred income taxes, net
$
15

 
$
15

Total assets of discontinued operations
$
15

 
$
15

Liabilities of discontinued operations
 
 
 
Accounts payable and other current obligations
$
2

 
$
1

Asset retirement obligations
30

 
32

Total liabilities of discontinued operations
$
32

 
$
33

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 Corporation from continuing operations for the three and six months ended June 30, 2015 and 2014, and total assets of continuing operations as of June 30, 2015, and December 31, 2014:
Three Months
Ameren
Missouri
 
Ameren
Illinois
 
Other
 
Intersegment
Eliminations
 
Ameren
 
2015
 
 
 
 
 
 
 
 
 
 
External revenues
$
872

 
$
512

 
$
17

  
$
—

 
$
1,401

 
Intersegment revenues
12

 
1

 
—

  
(13
)
 
—

 
Net income attributable to Ameren Corporation from continuing operations
61

 
31

 
6

 
—

 
98

 
2014
 
 
 
 
 
 
 
 
 
 
External revenues
$
893

 
$
518

 
$
8

 
$
—

 
$
1,419

 
Intersegment revenues
7

 
1

 
—

 
(8
)
 
—

 
Net income (loss) attributable to Ameren Corporation from continuing operations
126

 
28

 
(4
)
 
—

 
150

 
Six Months
  
 
  
 
  
 
  
 
  
 
2015
 
 
 
 
 
 
 
 
 
 
External revenues
$
1,665

 
$
1,256

 
$
36

 
$
—

 
$
2,957

 
Intersegment revenues
19

 
2

 
1

 
(22
)
 
—

 
Net income attributable to Ameren Corporation from continuing operations
102

 
84

 
20

 
—

 
206

 
2014
 
 
 
 
 
 
 
 
 
 
External revenues
$
1,704

 
$
1,292

 
$
17

 
$
—

 
$
3,013

 
Intersegment revenues
13

 
1

 
1

 
(15
)
 
—

 
Net income (loss) attributable to Ameren Corporation from continuing operations
173

 
81

 
(7
)
 
—

 
247

 
As of June 30, 2015:
 
 
 
 
 
 
 
 
 
 
Total assets
$
13,721

 
$
8,500

 
$
1,036

 
$
(120
)
 
$
23,137

(a) 
As of December 31, 2014:
 
 
 
 
 
 
 
 
 
 
Total assets
$
13,541

 
$
8,381

 
$
942

 
$
(203
)
 
$
22,661

(a) 
(a)    Excludes total assets from discontinued operations of $15 million as of June 30, 2015, and December 31, 2014.
Summary Of Significant Accounting Policies (Narrative) (Detail) (USD $)
In Millions, unless otherwise specified
Jun. 30, 2015
Basis Of Presentation And Significant Accounting Policies [Line Items]
 
Debt Issuance Cost
$ 36 
Union Electric Company
 
Basis Of Presentation And Significant Accounting Policies [Line Items]
 
Debt Issuance Cost
20 
Ameren Illinois Company
 
Basis Of Presentation And Significant Accounting Policies [Line Items]
 
Debt Issuance Cost
$ 16 
Summary Of Significant Accounting Policies Summary of Significant Accounting Policies (Schedule of Asset Retirement Obligations) (Details) (USD $)
In Millions, unless otherwise specified
6 Months Ended
Jun. 30, 2015
Dec. 31, 2014
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
 
 
Asset Retirement Obligation
$ 589 
$ 396 
Asset Retirement Obligation, Accretion Expense
11 1
 
Asset Retirement Obligation, Revision of Estimate
182 2
 
Union Electric Company
 
 
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
 
 
Asset Retirement Obligation
582 
389 
Asset Retirement Obligation, Accretion Expense
11 1
 
Asset Retirement Obligation, Revision of Estimate
182 2
 
Ameren Illinois Company
 
 
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
 
 
Asset Retirement Obligation
7 3
7 3
Asset Retirement Obligation, Accretion Expense
1 1 4
 
Asset Retirement Obligation, Revision of Estimate
1 2 4
 
Callaway energy center decommissioning study
 
 
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
 
 
Asset Retirement Obligation, Revision of Estimate
99 
 
Callaway energy center decommissioning study |
Union Electric Company
 
 
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
 
 
Asset Retirement Obligation, Revision of Estimate
99 
 
New CCR Rules Estimate
 
 
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
 
 
Asset Retirement Obligation, Revision of Estimate
79 
 
New CCR Rules Estimate |
Union Electric Company
 
 
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
 
 
Asset Retirement Obligation, Revision of Estimate
79 
 
Other Estimate Changes
 
 
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
 
 
Asset Retirement Obligation, Revision of Estimate
4 
 
Other Estimate Changes |
Union Electric Company
 
 
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
 
 
Asset Retirement Obligation, Revision of Estimate
$ 4 
 
[2] The ARO increase resulted in a corresponding increase recorded to “Property and Plant, Net.” During the first quarter of 2015, Ameren and Ameren Missouri increased their AROs related to the decommissioning of the Callaway energy center by $99 million to reflect the 2015 cost study and funding analysis filed with the MoPSC, extension of the estimated operating life until 2044, and a reduction in the discount rate assumption. See Note 10 - Callaway Energy Center for additional information. In addition, during the second quarter of 2015, as a result of new federal regulations, Ameren and Ameren Missouri recorded an increase of $79 million to their AROs associated with CCR storage facilities. See Note 9 - Commitments and Contingencies for additional information. Also during the second quarter of 2015, Ameren and Ameren Missouri increased their AROs by $4 million due to a change in the estimated retirement dates of the Meramec and Rush Island energy centers as a result of the MoPSC’s April 2015 electric rate order.
Summary Of Significant Accounting Policies (Schedule Of Excise Taxes) (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 6 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Jun. 30, 2014
Accounting Policies [Line Items]
 
 
 
 
Excise tax expense
$ 51 
$ 50 
$ 108 
$ 110 
Union Electric Company
 
 
 
 
Accounting Policies [Line Items]
 
 
 
 
Excise tax expense
41 
39 
75 
73 
Ameren Illinois Company
 
 
 
 
Accounting Policies [Line Items]
 
 
 
 
Excise tax expense
$ 10 
$ 11 
$ 33 
$ 37 
Summary Of Significant Accounting Policies Summary of Significant Accounting Policies (Schedule of Unrecognized Tax Benefits (Detriments)) (Details) (USD $)
In Millions, unless otherwise specified
6 Months Ended
Jun. 30, 2015
Dec. 31, 2014
Jun. 30, 2015
Union Electric Company
Dec. 31, 2014
Union Electric Company
Jun. 30, 2015
Ameren Illinois Company
Dec. 31, 2014
Ameren Illinois Company
Jun. 30, 2015
2013 Tax Year
Schedule of Unrecognized Tax Benefits (Detriments) [Line Items]
 
 
 
 
 
 
 
Unrecognized tax benefits (detriments)
$ 0 
$ 54 
$ 0 
$ 0 
$ 0 
$ (1)
 
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit
 
 
 
 
 
 
$ 53 
Summary Of Significant Accounting Policies Summary of Significant Accounting Policies (Schedule of Unrecognized Tax Benefits (Detriments) That Would Impact the Effective Tax Rate) (Details) (USD $)
In Millions, unless otherwise specified
Jun. 30, 2015
Dec. 31, 2014
Schedule of Unrecognized Tax Benefits (Detriments) That Would Impact Effective Tax Rate [Line Items]
 
 
Unrecognized tax benefits (detriments) that would impact effective tax rate
    
$ 52 
Union Electric Company
 
 
Schedule of Unrecognized Tax Benefits (Detriments) That Would Impact Effective Tax Rate [Line Items]
 
 
Unrecognized tax benefits (detriments) that would impact effective tax rate
   
0 
Ameren Illinois Company
 
 
Schedule of Unrecognized Tax Benefits (Detriments) That Would Impact Effective Tax Rate [Line Items]
 
 
Unrecognized tax benefits (detriments) that would impact effective tax rate
    
$ (1)
Rate And Regulatory Matters (Narrative-Missouri) (Detail) (USD $)
6 Months Ended 3 Months Ended 6 Months Ended 12 Months Ended 30 Months Ended 1 Months Ended 6 Months Ended 1 Months Ended
Jun. 30, 2015
Union Electric Company
Jun. 30, 2015
Electric Distribution
Union Electric Company
MEEIA
Jun. 30, 2015
Electric Distribution
Union Electric Company
MEEIA
Dec. 31, 2012
Electric Distribution
Union Electric Company
MEEIA
Jun. 30, 2015
Electric Distribution
Union Electric Company
MEEIA
Apr. 30, 2015
Electric Distribution
Union Electric Company
Final Rate Order
Jun. 30, 2015
Illinois Rivers Project
Ameren Transmission Company of Illinois
mi
Jun. 30, 2015
Mark Twain Project
Ameren Transmission Company of Illinois
mi
Apr. 30, 2015
Electric Distribution - Net Energy Costs
Union Electric Company
Final Rate Order
Apr. 30, 2015
Electric Distribution - Non-Energy Costs
Union Electric Company
Final Rate Order
Rate And Regulatory Matters [Line Items]
 
 
 
 
 
 
 
 
 
 
Public Utilities, Approved Rate Increase (Decrease), Amount
 
 
 
 
 
$ 122,000,000 
 
 
$ 109,000,000 
$ 13,000,000 
Public Utilities, Approved Return on Equity, Percentage
 
 
 
 
 
9.53% 
 
 
 
 
Public Utilities, Approved Equity Capital Structure, Percentage
 
 
 
 
 
51.80% 
 
 
 
 
Rate Base
 
 
 
 
 
7,000,000,000 
 
 
 
 
Energy Efficiency Program Spending
 
197,000,000 
 
147,000,000 
95,000,000 
 
 
 
 
 
Net Shared Benefits
 
65,000,000 
 
100,000,000 
115,000,000 
 
 
 
 
 
Incentive Award if Energy Efficiency Goals Are Achieved
 
$ 30,000,000 
 
$ 19,000,000 
 
 
 
 
 
 
Achieved Percentage of Energy Efficiency Earnings For Incentive Award
 
100.00% 
100.00% 
100.00% 
100.00% 
 
 
 
 
 
Incentive Award if Energy Efficiency Goals Are Achieved, Period of Recognition
 
 
2 years 
 
 
 
 
 
 
 
Energy Efficiency Program Spending Period
 
3 years 
 
 
 
 
 
 
 
 
Net Shared Benefits, Recognition Period
 
3 years 
 
 
 
 
 
 
 
 
Incentive Award if Energy Efficiency Goals Are Achieved, Period
 
3 years 
 
 
 
 
 
 
 
 
Minimum Percentage of Energy Efficiency Goal Achievement For Company To Be Eligible For Incentive Award
 
70.00% 
 
 
 
 
 
 
 
 
Percentage of Customer's Sales Volume
5.00% 
 
 
 
 
 
 
 
 
 
Transmission Line Miles
 
 
 
 
 
 
7 
100 
 
 
Rate And Regulatory Matters (Narrative-Illinois) (Detail) (USD $)
6 Months Ended 3 Months Ended 12 Months Ended 6 Months Ended 1 Months Ended 3 Months Ended
Jun. 30, 2015
Dec. 31, 2014
Jun. 30, 2015
Ameren Illinois Company
Dec. 31, 2014
Ameren Illinois Company
Jun. 30, 2015
Ameren Illinois Company
Electric Distribution
Final Rate Order
Sep. 30, 2015
Ameren Illinois Company
Gas Distribution
Pending Rate Case
Subsequent Event
Dec. 31, 2014
Ameren Illinois Company
Gas Distribution
Final Rate Order
Dec. 31, 2014
Ameren Illinois Company
Gas Distribution
Rate order appeal
Jun. 30, 2015
Ameren Transmission Company of Illinois
Spoon River Project
mi
Apr. 30, 2015
IEIMA
Ameren Illinois Company
Electric Distribution
2015 IEMA Revenue Requirement Reconciliation
Jun. 30, 2015
IEIMA
Ameren Illinois Company
Electric Distribution
2015 IEMA Revenue Requirement Reconciliation
Jun. 30, 2015
IEIMA
Ameren Illinois Company
Electric Distribution
2014 IEMA Revenue Requirement Reconciliation
Jun. 30, 2015
IEIMA
Ameren Illinois Company
Electric Distribution
2013 IEMA Revenue Requirement Reconciliation
Sep. 30, 2015
Icc Staff Recommendation
IEIMA
Ameren Illinois Company
Electric Distribution
2015 IEMA Revenue Requirement Reconciliation
Subsequent Event
Rate And Regulatory Matters [Line Items]
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Regulatory assets
$ 1,560,000,000 
$ 1,582,000,000 
$ 893,000,000 
$ 883,000,000 
 
 
 
 
 
 
$ 24,000,000 
$ 102,000,000 
$ 36,000,000 
 
Public Utilities, Requested Rate Increase (Decrease), Amount
 
 
 
 
 
45,000,000 
 
 
 
110,000,000 
 
 
 
107,000,000 
Public Utilities, Requested Return on Equity, Percentage
 
 
 
 
 
9.60% 
 
 
 
 
 
 
 
 
Public Utilities, Requested Equity Capital Structure, Percentage
 
 
 
 
 
50.00% 
 
 
 
 
 
 
 
 
Rate Base
 
 
 
 
 
1,200,000,000 
 
 
 
 
 
 
 
 
Public Utilities, Approved Return on Equity, Percentage
 
 
 
 
 
 
9.10% 
10.40% 
 
 
 
 
 
 
Public Utilities, Approved Rate Increase (Decrease), Amount
 
 
 
 
$ 15,000,000 
 
 
 
 
 
 
 
 
 
Transmission Line Miles
 
 
 
 
 
 
 
 
35 
 
 
 
 
 
Rate And Regulatory Matters (Narrative-Federal) (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 6 Months Ended 6 Months Ended 3 Months Ended 6 Months Ended 6 Months Ended 1 Months Ended 6 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2012
Jun. 30, 2015
Jun. 30, 2014
Dec. 31, 2014
Jun. 30, 2015
New Nuclear Energy Center COL
Jun. 30, 2015
Ameren Illinois Company
Dec. 31, 2014
Ameren Illinois Company
Jun. 30, 2015
Ameren Illinois Company
Final Rate Order
Jun. 30, 2015
Union Electric Company
Jun. 30, 2014
Union Electric Company
Jun. 30, 2015
Union Electric Company
Jun. 30, 2014
Union Electric Company
Dec. 31, 2014
Union Electric Company
Jun. 30, 2015
Union Electric Company
New Nuclear Energy Center COL
Feb. 28, 2015
Midwest Independent Transmission System Operator, Inc
Pending Ferc Case
Jun. 30, 2015
Midwest Independent Transmission System Operator, Inc
Pending Ferc Case
Jun. 30, 2015
Midwest Independent Transmission System Operator, Inc
Pending Ferc Case
Ameren Illinois Company
Rate And Regulatory Matters [Line Items]
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Loss Contingency, Estimate of Possible Loss
 
 
 
 
 
 
 
 
 
$ 8 
 
 
 
 
 
 
 
 
 
Current regulatory liabilities
120 
 
 
120 
 
106 
 
53 
84 
6 
58 
 
58 
 
18 
 
 
 
 
Payments for Legal Settlements
 
 
 
 
 
 
 
 
 
2 
 
 
 
 
 
 
 
 
 
Customer Requested Rate on Equity
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
8.67% 
9.15% 
 
Public Utilities, Approved Return on Equity, Percentage
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
12.38% 
 
Basis point reduction in FERC allowed base return on common equity
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
0.50% 
 
Earnings reduction in FERC allowed base return on common equity
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
4 
2 
Incentive adder to FERC allowed base return on common equity
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
0.50% 
 
Investments in Power and Distribution Projects
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
69 
 
 
 
Provision for Callaway construction and operating license
$ 69 
$ 0 
$ 0 
$ 69 
$ 0 
 
$ 69 
 
 
 
$ 69 
$ 0 
$ 69 
$ 0 
 
$ 69 
 
 
 
Short-Term Debt And Liquidity (Narrative) (Detail) (USD $)
3 Months Ended 6 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Jun. 30, 2014
Utilities
 
 
 
 
Line of Credit Facility [Line Items]
 
 
 
 
Short Term Debt, Weighted Average Interest Rate During Period
0.08% 
0.19% 
0.08% 
0.29% 
Credit Agreements 2012
 
 
 
 
Line of Credit Facility [Line Items]
 
 
 
 
Line of credit facility, maximum borrowing capacity
$ 1,200,000,000 
 
$ 1,200,000,000 
 
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
0.50 
 
0.50 
 
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
Jun. 30, 2015
Dec. 31, 2014
Line of Credit Facility [Line Items]
 
 
Commercial paper outstanding
$ 886 
$ 714 
Ameren (parent)
 
 
Line of Credit Facility [Line Items]
 
 
Commercial paper outstanding
836 
585 
Union Electric Company
 
 
Line of Credit Facility [Line Items]
 
 
Commercial paper outstanding
38 
97 
Ameren Illinois Company
 
 
Line of Credit Facility [Line Items]
 
 
Commercial paper outstanding
$ 12 
$ 32 
Short-Term Debt And Liquidity Short-Term Debt and Liquidity (Commercial Paper) (Details) (USD $)
In Millions, unless otherwise specified
6 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Line of Credit Facility [Line Items]
 
 
Average Daily Commercial Paper Borrowings Outstanding
$ 843 
$ 607 
Weighted Average Interest Rate
0.56% 
0.32% 
Peak Short Term Borrowings
1,108 1
907 1
Peak Short Term Borrowings Interest Rate
0.70% 
0.70% 
Ameren (parent)
 
 
Line of Credit Facility [Line Items]
 
 
Average Daily Commercial Paper Borrowings Outstanding
754 
328 
Weighted Average Interest Rate
0.57% 
0.32% 
Peak Short Term Borrowings
849 1
503 1
Peak Short Term Borrowings Interest Rate
0.70% 
0.35% 
Union Electric Company
 
 
Line of Credit Facility [Line Items]
 
 
Average Daily Commercial Paper Borrowings Outstanding
84 
146 
Weighted Average Interest Rate
0.50% 
0.31% 
Peak Short Term Borrowings
294 1
495 1
Peak Short Term Borrowings Interest Rate
0.60% 
0.70% 
Ameren Illinois Company
 
 
Line of Credit Facility [Line Items]
 
 
Average Daily Commercial Paper Borrowings Outstanding
5 
242 
Weighted Average Interest Rate
0.44% 
0.32% 
Peak Short Term Borrowings
$ 39 1
$ 300 1
Peak Short Term Borrowings Interest Rate
0.60% 
0.34% 
Long-Term Debt And Equity Financings (Narrative) (Detail) (USD $)
6 Months Ended 1 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Union Electric Company
Jun. 30, 2014
Union Electric Company
Jun. 30, 2015
Ameren Missouri And Ameren Illinois
Jun. 30, 2015
Ameren Illinois Company
Jun. 30, 2014
Ameren Illinois Company
Jun. 30, 2015
Ameren Illinois Company
Federal Energy Regulatory Commission Restriction
Jun. 30, 2015
Ameren Illinois Company
Minimum
Federal Energy Regulatory Commission Restriction
Apr. 30, 2015
Secured Debt
Senior Secured Notes, 3.65%, Due 2045
Union Electric Company
Apr. 30, 2015
Secured Debt
Senior Secured Notes 4.75% Due 2015
Union Electric Company
Long-Term Debt And Equity Financings [Line Items]
 
 
 
 
 
 
 
 
 
 
 
Capital contribution from parent
 
 
$ 224,000,000 
$ 0 
 
 
 
 
 
 
 
Debt Instrument, Face Amount
 
 
 
 
 
 
 
 
 
250,000,000 
 
Redemptions of Long-term Debt
114,000,000 
692,000,000 
114,000,000 
104,000,000 
 
0 
163,000,000 
 
 
 
114,000,000 
Debt Instrument, Interest Rate, Stated Percentage
 
 
 
 
 
 
 
 
 
3.65% 
4.75% 
Proceeds from Issuance of Secured Debt
 
 
 
 
 
 
 
 
 
$ 247,000,000 
 
Assumed interest rate
 
 
 
 
5.00% 
 
 
 
 
 
 
Dividend rate
 
 
 
 
6.00% 
 
 
 
 
 
 
Common stock equity to total capitalization
 
 
 
 
 
 
 
53.00% 
30.00% 
 
 
Long-Term Debt And Equity Financings (Schedule Of Covered Ratio) (Detail) (USD $)
In Millions, unless otherwise specified
6 Months Ended
Jun. 30, 2015
Union Electric Company
 
Long-Term Debt And Equity Financings [Line Items]
 
Bonds Issuable
$ 3,305 1
Preferred Stock Issuable
2,095 
Retired bond capacity
946 
Union Electric Company |
Actual Ratio [Member]
 
Long-Term Debt And Equity Financings [Line Items]
 
Restricted payment interest coverage ratio, Actual
3.5 
Dividend Coverage Ratio
94.4 
Ameren Illinois Company
 
Long-Term Debt And Equity Financings [Line Items]
 
Bonds Issuable
3,533 1 2
Preferred Stock Issuable
203 3
Retired bond capacity
$ 204 
Ameren Illinois Company |
Actual Ratio [Member]
 
Long-Term Debt And Equity Financings [Line Items]
 
Restricted payment interest coverage ratio, Actual
6.7 
Dividend Coverage Ratio
2.8 
Minimum |
Union Electric Company |
Minimum Required Ratio [Member]
 
Long-Term Debt And Equity Financings [Line Items]
 
Restricted payment interest coverage ratio, Actual
2.0 4
Dividend Coverage Ratio
2.5 5
Minimum |
Ameren Illinois Company |
Minimum Required Ratio [Member]
 
Long-Term Debt And Equity Financings [Line Items]
 
Restricted payment interest coverage ratio, Actual
2.0 4
Dividend Coverage Ratio
1.5 5
Other Income and Expenses (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 6 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Jun. 30, 2014
Other Nonoperating Income (Expense) [Line Items]
 
 
 
 
Allowance for equity funds used during construction
$ 6 1
$ 9 1
$ 11 1
$ 16 1
Interest income on industrial development revenue bonds
6 1
7 1
13 1
14 1
Interest and dividend income
4 1
2 1
8 1
5 1
Other
0 1
3 1
3 1
4 1
Total miscellaneous income
16 1
21 1
35 1
39 1
Donations
2 1
1 1
10 1
6 1
Other
4 1
3 1
7 1
7 1
Total miscellaneous expense
6 1
4 1
17 1
13 1
Union Electric Company
 
 
 
 
Other Nonoperating Income (Expense) [Line Items]
 
 
 
 
Allowance for equity funds used during construction
5 
8 
9 
15 
Interest income on industrial development revenue bonds
6 
7 
13 
14 
Interest and dividend income
1 
1 
1 
1 
Total miscellaneous income
12 
16 
23 
30 
Donations
1 
1 
3 
3 
Other
1 
1 
2 
3 
Total miscellaneous expense
2 
2 
5 
6 
Ameren Illinois Company
 
 
 
 
Other Nonoperating Income (Expense) [Line Items]
 
 
 
 
Allowance for equity funds used during construction
1 
1 
2 
1 
Interest and dividend income
3 
1 
7 
3 
Other
0 
3 
2 
4 
Total miscellaneous income
4 
5 
11 
8 
Donations
1 
 
4 
3 
Other
1 
1 
3 
2 
Total miscellaneous expense
$ 2 
$ 1 
$ 7 
$ 5 
Derivative Financial Instruments (Open Gross Derivative Volumes By Commodity Type) (Detail)
Jun. 30, 2015
gal
Dec. 31, 2014
gal
Fuel Oils
 
 
Derivative [Line Items]
 
 
Quantity
39,000,000 1
50,000,000 1
Natural Gas
 
 
Derivative [Line Items]
 
 
Quantity
156,000,000 
136,000,000 
Power
 
 
Derivative [Line Items]
 
 
Quantity
11,000,000 
12,000,000 
Uranium
 
 
Derivative [Line Items]
 
 
Quantity
316,000 
332,000 
Union Electric Company |
Fuel Oils
 
 
Derivative [Line Items]
 
 
Quantity
39,000,000 1
50,000,000 1
Union Electric Company |
Natural Gas
 
 
Derivative [Line Items]
 
 
Quantity
29,000,000 
28,000,000 
Union Electric Company |
Power
 
 
Derivative [Line Items]
 
 
Quantity
1,000,000 
1,000,000 
Union Electric Company |
Uranium
 
 
Derivative [Line Items]
 
 
Quantity
316,000 
332,000 
Ameren Illinois Company |
Natural Gas
 
 
Derivative [Line Items]
 
 
Quantity
127,000,000 
108,000,000 
Ameren Illinois Company |
Power
 
 
Derivative [Line Items]
 
 
Quantity
10,000,000 
11,000,000 
Derivative Financial Instruments (Derivative Instruments Carrying Value) (Detail) (Not Designated As Hedging Instrument, USD $)
In Millions, unless otherwise specified
Jun. 30, 2015
Dec. 31, 2014
Derivative [Line Items]
 
 
Derivative assets
$ 31 
$ 19 
Derivative liabilities
237 
232 
Fuel Oils |
Other Current Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
1 
2 
Fuel Oils |
Other Current Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
14 
22 
Fuel Oils |
Other Deferred Credits And Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
5 
7 
Natural Gas |
Other Current Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
 
2 
Natural Gas |
Other Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
1 
 
Natural Gas |
Other Current Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
28 
37 
Natural Gas |
Other Deferred Credits And Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
21 
19 
Power |
Other Current Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
29 
15 
Power |
Other Current Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
13 
14 
Power |
Other Deferred Credits And Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
154 
131 
Uranium |
Other Current Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
2 
2 
Union Electric Company
 
 
Derivative [Line Items]
 
 
Derivative assets
30 
18 
Derivative liabilities
34 
46 
Union Electric Company |
Fuel Oils |
Other Current Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
1 
2 
Union Electric Company |
Fuel Oils |
Other Current Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
14 
22 
Union Electric Company |
Fuel Oils |
Other Deferred Credits And Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
5 
7 
Union Electric Company |
Natural Gas |
Other Current Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
 
1 
Union Electric Company |
Natural Gas |
Other Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
0 
 
Union Electric Company |
Natural Gas |
Other Current Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
4 
6 
Union Electric Company |
Natural Gas |
Other Deferred Credits And Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
7 
6 
Union Electric Company |
Power |
Other Current Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
29 
15 
Union Electric Company |
Power |
Other Current Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
2 
3 
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 
2 
Ameren Illinois Company
 
 
Derivative [Line Items]
 
 
Derivative assets
1 
1 
Derivative liabilities
203 
186 
Ameren Illinois Company |
Fuel Oils |
Other Current Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
0 
0 
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
 
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
14 
13 
Ameren Illinois Company |
Natural Gas |
Mark To Market Derivative Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
24 
31 
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
154 
131 
Ameren Illinois Company |
Power |
Mark To Market Derivative Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
11 
11 
Ameren Illinois Company |
Uranium |
Other Current Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
$ 0 
$ 0 
Derivative Financial Instruments (Cumulative Amount Of Pretax Net Gains (Losses) On All Derivative Instruments In OCI) (Detail) (USD $)
In Millions, unless otherwise specified
Jun. 30, 2015
Dec. 31, 2014
Derivative [Line Items]
 
 
Current gains deferred as regulatory liabilities
$ 120 
$ 106 
Current losses deferred as regulatory assets
223 
295 
Fuel Oils
 
 
Derivative [Line Items]
 
 
Current gains deferred as regulatory liabilities
1 
 
Current losses deferred as regulatory assets
14 
 
Fuel Oils |
Regulatory Liabilities Or Assets [Member]
 
 
Derivative [Line Items]
 
 
Cumulative deferred pretax gains (losses)
(19)1
(29)
Natural Gas
 
 
Derivative [Line Items]
 
 
Current losses deferred as regulatory assets
28 
 
Natural Gas |
Regulatory Liabilities Or Assets [Member]
 
 
Derivative [Line Items]
 
 
Cumulative deferred pretax gains (losses)
(48)2
(54)
Power
 
 
Derivative [Line Items]
 
 
Current gains deferred as regulatory liabilities
29 
 
Current losses deferred as regulatory assets
13 
 
Power |
Regulatory Liabilities Or Assets [Member]
 
 
Derivative [Line Items]
 
 
Cumulative deferred pretax gains (losses)
(138)3
(130)
Uranium
 
 
Derivative [Line Items]
 
 
Current losses deferred as regulatory assets
2 
 
Uranium |
Regulatory Liabilities Or Assets [Member]
 
 
Derivative [Line Items]
 
 
Cumulative deferred pretax gains (losses)
(2)4
(2)
Union Electric Company
 
 
Derivative [Line Items]
 
 
Current gains deferred as regulatory liabilities
58 
18 
Current losses deferred as regulatory assets
133 
163 
Union Electric Company |
Fuel Oils
 
 
Derivative [Line Items]
 
 
Current gains deferred as regulatory liabilities
1 
 
Current losses deferred as regulatory assets
14 
 
Union Electric Company |
Fuel Oils |
Regulatory Liabilities Or Assets [Member]
 
 
Derivative [Line Items]
 
 
Cumulative deferred pretax gains (losses)
(19)1
(29)
Union Electric Company |
Natural Gas
 
 
Derivative [Line Items]
 
 
Current losses deferred as regulatory assets
4 
 
Union Electric Company |
Natural Gas |
Regulatory Liabilities Or Assets [Member]
 
 
Derivative [Line Items]
 
 
Cumulative deferred pretax gains (losses)
(11)2
(11)
Union Electric Company |
Power
 
 
Derivative [Line Items]
 
 
Current gains deferred as regulatory liabilities
29 
 
Current losses deferred as regulatory assets
2 
 
Union Electric Company |
Power |
Regulatory Liabilities Or Assets [Member]
 
 
Derivative [Line Items]
 
 
Cumulative deferred pretax gains (losses)
27 3
12 
Union Electric Company |
Uranium
 
 
Derivative [Line Items]
 
 
Current losses deferred as regulatory assets
2 
 
Union Electric Company |
Uranium |
Regulatory Liabilities Or Assets [Member]
 
 
Derivative [Line Items]
 
 
Cumulative deferred pretax gains (losses)
(2)4
(2)
Ameren Illinois Company
 
 
Derivative [Line Items]
 
 
Current gains deferred as regulatory liabilities
53 
84 
Current losses deferred as regulatory assets
89 
129 
Ameren Illinois Company |
Fuel Oils |
Regulatory Liabilities Or Assets [Member]
 
 
Derivative [Line Items]
 
 
Cumulative deferred pretax gains (losses)
0 1
0 
Ameren Illinois Company |
Natural Gas
 
 
Derivative [Line Items]
 
 
Current losses deferred as regulatory assets
24 
 
Ameren Illinois Company |
Natural Gas |
Regulatory Liabilities Or Assets [Member]
 
 
Derivative [Line Items]
 
 
Cumulative deferred pretax gains (losses)
(37)2
(43)
Ameren Illinois Company |
Power
 
 
Derivative [Line Items]
 
 
Current losses deferred as regulatory assets
11 
 
Ameren Illinois Company |
Power |
Regulatory Liabilities Or Assets [Member]
 
 
Derivative [Line Items]
 
 
Cumulative deferred pretax gains (losses)
(165)3
(142)
Ameren Illinois Company |
Uranium |
Regulatory Liabilities Or Assets [Member]
 
 
Derivative [Line Items]
 
 
Cumulative deferred pretax gains (losses)
$ 0 4
$ 0 
Derivative Financial Instruments (Offsetting Derivative Assets and Liabilities) (Details) (Commodity Contract, USD $)
In Millions, unless otherwise specified
Jun. 30, 2015
Dec. 31, 2014
Offsetting Assets and Liabilities [Line Items]
 
 
Gross Amounts Recognized in the Balance Sheet
$ 31 1
$ 19 1
Derivative Instruments
3 
5 
Derivative, Collateral, Obligation to Return Cash
0 2
0 2
Net Amount
28 
14 
Gross Amounts Recognized in the Balance Sheet
237 1
232 1
Derivative Instruments
3 
5 
Cash Collateral Received/Posted
2 2
5 2
Net Amount
232 
222 
Union Electric Company
 
 
Offsetting Assets and Liabilities [Line Items]
 
 
Gross Amounts Recognized in the Balance Sheet
30 1
18 1
Derivative Instruments
3 
5 
Derivative, Collateral, Obligation to Return Cash
0 2
0 2
Net Amount
27 
13 
Gross Amounts Recognized in the Balance Sheet
34 1
46 1
Derivative Instruments
3 
5 
Cash Collateral Received/Posted
2 2
5 2
Net Amount
29 
36 
Ameren Illinois Company
 
 
Offsetting Assets and Liabilities [Line Items]
 
 
Gross Amounts Recognized in the Balance Sheet
1 
1 
Derivative Instruments
0 
0 
Derivative, Collateral, Obligation to Return Cash
0 2
0 2
Net Amount
1 
1 
Gross Amounts Recognized in the Balance Sheet
203 1
186 1
Derivative Instruments
0 
0 
Cash Collateral Received/Posted
0 2
0 2
Net Amount
$ 203 
$ 186 
Derivative Financial Instruments (Maximum Exposure If Counterparties Fail To Perform On Contracts) (Detail) (USD $)
In Millions, unless otherwise specified
6 Months Ended
Jun. 30, 2015
Derivative [Line Items]
 
Maximum exposure to counterparties related to derivative contracts
$ 11 
Union Electric Company
 
Derivative [Line Items]
 
Maximum exposure to counterparties related to derivative contracts
11 
Ameren Illinois Company
 
Derivative [Line Items]
 
Maximum exposure to counterparties related to derivative contracts
$ 0 
Derivative Financial Instruments (Potential Loss On Counterparty Exposures) (Detail) (USD $)
In Millions, unless otherwise specified
Jun. 30, 2015
Concentration Risk [Line Items]
 
Potential loss on counterparty exposures related to derivative contracts
$ 11 
Ameren Illinois Company
 
Concentration Risk [Line Items]
 
Potential loss on counterparty exposures related to derivative contracts
0 
Union Electric Company
 
Concentration Risk [Line Items]
 
Potential loss on counterparty exposures related to derivative contracts
$ 11 
Fair Value Measurements (Schedule Of Valuation Process And Unobservable Inputs) (Detail) (USD $)
In Millions, unless otherwise specified
6 Months Ended 12 Months Ended
Jun. 30, 2015
Dec. 31, 2014
Natural Gas |
Discounted Cash Flow |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
0.21% 1 2
0.43% 1 2
Nodal basis
(0.60)3
(0.40)3
Credit risk
0.40% 1 2
0.43% 1 2
Natural Gas |
Discounted Cash Flow |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
2.01% 1 2
13.00% 1 2
Nodal basis
0 3
0.10 3
Credit risk
0.40% 1 2
0.43% 1 2
Natural Gas |
Discounted Cash Flow |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
0.83% 1 2
3.00% 1 2
Nodal basis
(0.40)3
(0.20)3
Credit risk
0.40% 1 2
0.43% 1 2
Natural Gas |
Option Model |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
 
31.00% 1
Nodal basis
 
(0.40)3
Natural Gas |
Option Model |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
 
144.00% 1
Nodal basis
 
0 3
Natural Gas |
Option Model |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
 
63.00% 1
Nodal basis
 
(0.20)3
Natural Gas |
Derivative Assets
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative assets
$ 0 4
$ 1 4
Natural Gas |
Union Electric Company |
Discounted Cash Flow |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
 
0.57% 1 2
Nodal basis
 
(0.10)3
Credit risk
 
0.43% 1 2
Natural Gas |
Union Electric Company |
Discounted Cash Flow |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
 
13.00% 1 2
Nodal basis
 
(0.10)3
Credit risk
 
0.43% 1 2
Natural Gas |
Union Electric Company |
Discounted Cash Flow |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
 
5.00% 1 2
Nodal basis
 
(0.10)3
Credit risk
 
0.43% 1 2
Natural Gas |
Union Electric Company |
Option Model |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
 
31.00% 1
Nodal basis
 
(0.40)3
Natural Gas |
Union Electric Company |
Option Model |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
 
144.00% 1
Nodal basis
 
0 3
Natural Gas |
Union Electric Company |
Option Model |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
 
53.00% 1
Nodal basis
 
(0.30)3
Natural Gas |
Union Electric Company |
Derivative Assets
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative assets
 
0 4
Natural Gas |
Ameren Illinois Company |
Discounted Cash Flow |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
0.21% 1 2
0.43% 1 2
Nodal basis
(0.6)3
(0.40)3
Credit risk
0.40% 1 2
0.43% 1 2
Natural Gas |
Ameren Illinois Company |
Discounted Cash Flow |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
2.01% 1 2
2.00% 1 2
Nodal basis
0 3
0.10 3
Credit risk
0.40% 1 2
0.43% 1 2
Natural Gas |
Ameren Illinois Company |
Discounted Cash Flow |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
0.83% 1 2
0.83% 1 2
Nodal basis
(0.4)3
(0.20)3
Credit risk
0.40% 1 2
0.43% 1 2
Natural Gas |
Ameren Illinois Company |
Option Model |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
 
50.00% 1
Nodal basis
 
(0.10)3
Natural Gas |
Ameren Illinois Company |
Option Model |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
 
144.00% 1
Nodal basis
 
0 3
Natural Gas |
Ameren Illinois Company |
Option Model |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
 
94.00% 1
Nodal basis
 
(0.10)3
Natural Gas |
Ameren Illinois Company |
Derivative Assets
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative assets
0 4
1 4
Natural Gas |
Derivative Liabilities
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative liabilities
(1)4
(2)4
Natural Gas |
Derivative Liabilities |
Union Electric Company
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative liabilities
 
(1)4
Natural Gas |
Derivative Liabilities |
Ameren Illinois Company
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative liabilities
(1)4
(1)4
Fuel Oils |
Discounted Cash Flow |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Escalation rate
 
5.00% 3 5
Credit risk
0.40% 1 2
0.43% 1 2
Fuel Oils |
Discounted Cash Flow |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Escalation rate
 
5.00% 3 5
Credit risk
0.40% 1 2
0.43% 1 2
Fuel Oils |
Discounted Cash Flow |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Escalation rate
 
5.00% 3 5
Credit risk
0.40% 1 2
0.43% 1 2
Fuel Oils |
Option Model |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
32.00% 1
3.00% 1
Fuel Oils |
Option Model |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
50.00% 1
39.00% 1
Fuel Oils |
Option Model |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
37.00% 1
32.00% 1
Fuel Oils |
Derivative Assets
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative assets
1 4
2 4
Fuel Oils |
Union Electric Company |
Discounted Cash Flow |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Escalation rate
 
5.00% 3 5
Credit risk
0.40% 1 2
0.43% 1 2
Fuel Oils |
Union Electric Company |
Discounted Cash Flow |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Escalation rate
 
5.00% 3 5
Credit risk
0.40% 1 2
0.43% 1 2
Fuel Oils |
Union Electric Company |
Discounted Cash Flow |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Escalation rate
 
5.00% 3 5
Credit risk
0.40% 1 2
0.43% 1 2
Fuel Oils |
Union Electric Company |
Option Model |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
32.00% 1
3.00% 1
Fuel Oils |
Union Electric Company |
Option Model |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
50.00% 1
39.00% 1
Fuel Oils |
Union Electric Company |
Option Model |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
37.00% 1
32.00% 1
Fuel Oils |
Union Electric Company |
Derivative Assets
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative assets
1 4
2 4
Fuel Oils |
Derivative Liabilities
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative liabilities
(2)4
(8)4
Fuel Oils |
Derivative Liabilities |
Union Electric Company
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative liabilities
(2)4
(8)4
Power |
Discounted Cash Flow |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
0.39% 1 2
0.26% 1 2
Nodal basis
(11)3
(6)3
Credit risk
0.40% 1 2
0.43% 1 2
Average forward peak and off-peak pricing
26 6
27 7
Estimated auction price
(1,006)3
(1,833)3
Power |
Discounted Cash Flow |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
13.86% 1 2
0.26% 1 2
Nodal basis
(1)3
0 3
Credit risk
0.40% 1 2
0.43% 1 2
Average forward peak and off-peak pricing
45 6
50 7
Estimated auction price
1,606 3
2,743 3
Power |
Discounted Cash Flow |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
8.64% 1 2
0.26% 1 2
Nodal basis
(3)3
(2)3
Credit risk
0.40% 1 2
0.43% 1 2
Average forward peak and off-peak pricing
31 6
32 7
Estimated auction price
184 3
171 3
Power |
Fundamental Energy Production Model |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Escalation rate
2.00% 3 8
0.00% 3 9
Estimated future gas prices
3 3
4 3
Power |
Fundamental Energy Production Model |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Escalation rate
2.00% 3 8
1.00% 3 9
Estimated future gas prices
6 3
5 3
Power |
Fundamental Energy Production Model |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Escalation rate
2.00% 3 8
1.00% 3 9
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
29 10 4
11 11 4
Power |
Union Electric Company |
Discounted Cash Flow |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
0.39% 1 2
0.26% 1 2
Nodal basis
(11)1
 
Credit risk
 
0.43% 1 2
Average forward peak and off-peak pricing
26 1
27 1
Estimated auction price
(1,006)3
(1,833)3
Power |
Union Electric Company |
Discounted Cash Flow |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
13.86% 1 2
0.26% 1 2
Nodal basis
(4)1
 
Credit risk
 
0.43% 1 2
Average forward peak and off-peak pricing
45 1
50 1
Estimated auction price
1,606 3
2,743 3
Power |
Union Electric Company |
Discounted Cash Flow |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
8.64% 1 2
0.26% 1 2
Nodal basis
(9)1
 
Credit risk
 
0.43% 1 2
Average forward peak and off-peak pricing
34 1
32 1
Estimated auction price
184 3
171 3
Power |
Union Electric Company |
Derivative Assets
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative assets
29 10 4
11 11 4
Power |
Ameren Illinois Company |
Discounted Cash Flow |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Nodal basis
(6)3
(6)3
Credit risk
0.40% 1 2
0.43% 1 2
Average forward peak and off-peak pricing
27 3
 
Average forward pricing
 
27 3
Power |
Ameren Illinois Company |
Discounted Cash Flow |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Nodal basis
(1)3
0 3
Credit risk
0.40% 1 2
0.43% 1 2
Average forward peak and off-peak pricing
37 3
 
Average forward pricing
 
38 3
Power |
Ameren Illinois Company |
Discounted Cash Flow |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Nodal basis
(3)3
(2)3
Credit risk
0.40% 1 2
0.43% 1 2
Average forward peak and off-peak pricing
30 3
 
Average forward pricing
 
32 3
Power |
Ameren Illinois Company |
Fundamental Energy Production Model |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Escalation rate
2.00% 3 8
0.00% 3 9
Estimated future gas prices
3 3
4 3
Power |
Ameren Illinois Company |
Fundamental Energy Production Model |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Escalation rate
2.00% 3 8
1.00% 3 9
Estimated future gas prices
6 3
5 3
Power |
Ameren Illinois Company |
Fundamental Energy Production Model |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Escalation rate
2.00% 3 8
1.00% 3 9
Estimated future gas prices
4 3
4 3
Power |
Ameren Illinois Company |
Contract Price Allocation |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Estimated renewable energy credit costs
5 3
5 3
Power |
Ameren Illinois Company |
Contract Price Allocation |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Estimated renewable energy credit costs
7 3
7 3
Power |
Ameren Illinois Company |
Contract Price Allocation |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Estimated renewable energy credit costs
6 3
6 3
Power |
Ameren Illinois Company |
Derivative Assets
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative assets
0 10 4
0 11 4
Power |
Derivative Liabilities
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative liabilities
(167)10 4
(144)11 4
Power |
Derivative Liabilities |
Union Electric Company
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative liabilities
(2)10 4
(2)11 4
Power |
Derivative Liabilities |
Ameren Illinois Company
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative liabilities
(165)10 4
(142)11 4
Uranium |
Discounted Cash Flow |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Average forward pricing
36 3
35 3
Uranium |
Discounted Cash Flow |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Average forward pricing
39 3
40 3
Uranium |
Discounted Cash Flow |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Average forward pricing
37 3
36 3
Uranium |
Derivative Assets
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative assets
0 4
0 4
Uranium |
Union Electric Company |
Discounted Cash Flow |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Average forward pricing
36 3
35 3
Uranium |
Union Electric Company |
Discounted Cash Flow |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Average forward pricing
39 3
40 3
Uranium |
Union Electric Company |
Discounted Cash Flow |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Average forward pricing
37 3
36 3
Uranium |
Union Electric Company |
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
(2)4
(2)4
Uranium |
Derivative Liabilities |
Union Electric Company
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative liabilities
$ (2)4
$ (2)4
Fair Value Measurements (Narrative) (Detail) (USD $)
In Millions, unless otherwise specified
Jun. 30, 2015
Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
 
 
Valuation adjustments related to net derivative contracts, liabilities
$ 1 
$ 1 
Union Electric Company
 
 
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
 
 
Valuation adjustments related to net derivative contracts, liabilities
1 
1 
Ameren Illinois Company
 
 
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
 
 
Valuation adjustments related to net derivative contracts, liabilities
$ 1 
$ 1 
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
Jun. 30, 2015
Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
$ 557 1
$ 547 2
Assets fair value
588 3
566 3
Excluded receivables, payables, and accrued income, net
(2)
2 
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
557 1
547 2
Assets fair value
587 3
565 3
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
31 3
19 3
Derivative liabilities
237 3
232 3
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
30 3
18 3
Derivative liabilities
34 3
46 3
Commodity Contract |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
1 
1 
Derivative liabilities
203 3
186 3
Commodity Contract |
Fuel Oils
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
1 3
2 3
Derivative liabilities
19 3
29 3
Commodity Contract |
Fuel Oils |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
1 3
2 3
Derivative liabilities
19 3
29 3
Commodity Contract |
Natural Gas
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
1 3
2 3
Derivative liabilities
49 3
56 3
Commodity Contract |
Natural Gas |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
 
1 3
Derivative liabilities
11 3
12 3
Commodity Contract |
Natural Gas |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
1 3
1 3
Derivative liabilities
38 3
44 3
Commodity Contract |
Power
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
29 3
15 3
Derivative liabilities
167 3
145 3
Commodity Contract |
Power |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
29 3
15 3
Derivative liabilities
2 3
3 3
Commodity Contract |
Power |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
165 3
142 3
Commodity Contract |
Uranium
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
2 3
2 3
Commodity Contract |
Uranium |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
2 3
2 3
Cash and cash equivalents
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
6 
1 
Cash and cash equivalents |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
6 
1 
Equity Securities |
U.S. large capitalization
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
370 
364 
Equity Securities |
U.S. large capitalization |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
370 
364 
Debt Securities |
Corporate bonds
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
59 
63 
Debt Securities |
Corporate bonds |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
59 
63 
Debt Securities |
US treasury and government securities
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
100 
102 
Debt Securities |
US treasury and government securities |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
100 
102 
Debt Securities |
Other Debt Securities
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
22 
17 
Debt Securities |
Other Debt Securities |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
22 
17 
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
376 
365 
Assets fair value
376 3
365 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
376 
365 
Assets fair value
376 3
365 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
17 3
22 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
17 3
22 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
0 
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract |
Fuel Oils
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 3
0 3
Derivative liabilities
17 3
21 3
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract |
Fuel Oils |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 3
0 3
Derivative liabilities
17 3
21 3
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract |
Natural Gas
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 3
0 3
Derivative liabilities
0 3
1 3
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract |
Natural Gas |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
 
0 3
Derivative liabilities
0 3
1 3
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract |
Natural Gas |
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
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract |
Power
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 3
0 3
Derivative liabilities
0 3
0 3
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract |
Power |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 3
0 3
Derivative liabilities
0 3
0 3
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract |
Power |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
0 3
0 3
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract |
Uranium
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
0 3
0 3
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract |
Uranium |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
0 3
0 3
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
6 
1 
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
6 
1 
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
370 
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
370 
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
181 
182 
Assets fair value
182 3
187 3
Significant Other Observable Inputs (Level 2) |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
181 
182 
Assets fair value
181 3
187 3
Significant Other Observable Inputs (Level 2) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
1 3
5 3
Derivative liabilities
48 3
54 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
5 3
Derivative liabilities
11 3
11 3
Significant Other Observable Inputs (Level 2) |
Commodity Contract |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
37 3
43 3
Significant Other Observable Inputs (Level 2) |
Commodity Contract |
Fuel Oils
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 3
0 3
Derivative liabilities
0 3
0 3
Significant Other Observable Inputs (Level 2) |
Commodity Contract |
Fuel Oils |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 3
0 3
Derivative liabilities
0 3
0 3
Significant Other Observable Inputs (Level 2) |
Commodity Contract |
Natural Gas
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
1 3
1 3
Derivative liabilities
48 3
53 3
Significant Other Observable Inputs (Level 2) |
Commodity Contract |
Natural Gas |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
 
1 3
Derivative liabilities
11 3
10 3
Significant Other Observable Inputs (Level 2) |
Commodity Contract |
Natural Gas |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
1 3
0 3
Derivative liabilities
37 3
43 3
Significant Other Observable Inputs (Level 2) |
Commodity Contract |
Power
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 3
4 3
Derivative liabilities
0 3
1 3
Significant Other Observable Inputs (Level 2) |
Commodity Contract |
Power |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 3
4 3
Derivative liabilities
0 3
1 3
Significant Other Observable Inputs (Level 2) |
Commodity Contract |
Power |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
0 3
0 
Significant Other Observable Inputs (Level 2) |
Commodity Contract |
Uranium
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
0 3
0 3
Significant Other Observable Inputs (Level 2) |
Commodity Contract |
Uranium |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
0 3
0 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
59 
63 
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
59 
63 
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
100 
102 
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
100 
102 
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
22 
17 
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
22 
17 
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
30 3
14 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
30 3
13 3
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
30 3
14 3
Derivative liabilities
172 3
156 3
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
30 3
13 3
Derivative liabilities
6 3
13 3
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
166 3
143 3
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract |
Fuel Oils
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
1 3
2 3
Derivative liabilities
2 3
8 3
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract |
Fuel Oils |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
1 3
2 3
Derivative liabilities
2 3
8 3
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract |
Natural Gas
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 3
1 3
Derivative liabilities
1 3
2 3
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract |
Natural Gas |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
 
0 3
Derivative liabilities
0 3
1 3
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract |
Natural Gas |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 3
1 3
Derivative liabilities
1 3
1 3
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract |
Power
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
29 3
11 3
Derivative liabilities
167 3
144 3
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract |
Power |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
29 3
11 3
Derivative liabilities
2 3
2 3
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract |
Power |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
165 3
142 3
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract |
Uranium
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
2 3
2 3
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract |
Uranium |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
2 3
2 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 
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) (USD $)
In Millions, unless otherwise specified
3 Months Ended 6 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Jun. 30, 2014
Fuel Oils
 
 
 
 
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
 
 
 
 
Beginning balance
$ (6)
$ 1 
$ (6)
$ 5 
Included in regulatory assets/liabilities
1 
1 
 
(1)
Settlements
2 
 
3 
(2)
Transfer out of Level 3
2 
0 
2 
0 
Ending balance
(1)
2 
(1)
2 
Change in unrealized gains (losses) related to assets/liabilities held at period end
3 
1 
0 
0 
Uranium
 
 
 
 
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
 
 
 
 
Beginning balance
(1)
(5)
(2)
(6)
Included in regulatory assets/liabilities
(1)
(4)
 
(4)
Settlements
 
2 
 
3 
Ending balance
(2)
(7)
(2)
(7)
Change in unrealized gains (losses) related to assets/liabilities held at period end
(1)
(4)
0 
(4)
Natural Gas
 
 
 
 
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
 
 
 
 
Beginning balance
0 
0 
(1)
0 
Purchases
(1)
1 
 
(1)
Settlements
0 
(1)
0 
1 
Ending balance
(1)
0 
(1)
0 
Change in unrealized gains (losses) related to assets/liabilities held at period end
0 
0 
0 
0 
Power
 
 
 
 
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
 
 
 
 
Beginning balance
(160)
(110)
(133)
(89)
Included in regulatory assets/liabilities
(4)
3 
(31)
(14)
Purchases
29 
34 
29 
34 
Settlements
(3)
(14)
(3)
(19)
Transfer out of Level 3
0 
(1)
 
 
Ending balance
(138)
(88)
(138)
(88)
Change in unrealized gains (losses) related to assets/liabilities held at period end
(4)
14 
(29)
(2)
Union Electric Company |
Fuel Oils
 
 
 
 
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
 
 
 
 
Beginning balance
(6)
1 
(6)
5 
Included in regulatory assets/liabilities
1 
1 
 
(1)
Settlements
2 
 
3 
(2)
Transfer out of Level 3
2 
0 
2 
0 
Ending balance
(1)
2 
(1)
2 
Change in unrealized gains (losses) related to assets/liabilities held at period end
3 
1 
0 
0 
Union Electric Company |
Uranium
 
 
 
 
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
 
 
 
 
Beginning balance
(1)
(5)
(2)
(6)
Included in regulatory assets/liabilities
(1)
(4)
 
(4)
Settlements
 
2 
 
3 
Ending balance
(2)
(7)
(2)
(7)
Change in unrealized gains (losses) related to assets/liabilities held at period end
(1)
(4)
0 
(4)
Union Electric Company |
Natural Gas
 
 
 
 
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
 
 
 
 
Beginning balance
(1)
0 
(1)
0 
Purchases
0 
0 
 
0 
Settlements
1 
0 
1 
0 
Ending balance
0 
0 
0 
0 
Change in unrealized gains (losses) related to assets/liabilities held at period end
0 
0 
0 
0 
Union Electric Company |
Power
 
 
 
 
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
 
 
 
 
Beginning balance
4 
10 
9 
19 
Included in regulatory assets/liabilities
0 
(13)
(2)
(18)
Purchases
29 
34 
29 
34 
Settlements
(6)
(15)
(9)
(20)
Transfer out of Level 3
0 
(1)
 
 
Ending balance
27 
15 
27 
15 
Change in unrealized gains (losses) related to assets/liabilities held at period end
1 
(1)
0 
(3)
Ameren Illinois Company |
Fuel Oils
 
 
 
 
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
 
 
 
 
Transfer out of Level 3
0 
0 
0 
0 
Ameren Illinois Company |
Natural Gas
 
 
 
 
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
 
 
 
 
Beginning balance
1 
0 
0 
0 
Purchases
(1)
1 
 
(1)
Settlements
(1)
(1)
(1)
1 
Ending balance
(1)
0 
(1)
0 
Change in unrealized gains (losses) related to assets/liabilities held at period end
0 
0 
0 
0 
Ameren Illinois Company |
Power
 
 
 
 
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
 
 
 
 
Beginning balance
(164)
(120)
(142)
(108)
Included in regulatory assets/liabilities
(4)
16 
(29)
4 
Purchases
0 
0 
0 
0 
Settlements
3 
1 
6 
1 
Transfer out of Level 3
0 
0 
 
 
Ending balance
(165)
(103)
(165)
(103)
Change in unrealized gains (losses) related to assets/liabilities held at period end
$ (5)
$ 15 
$ (29)
$ 1 
Fair Value Measurements (Schedule Of Transfers Between Fair Value Hierarchy Levels) (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 6 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Jun. 30, 2014
Fuel Oils
 
 
 
 
Derivative [Line Items]
 
 
 
 
Assets Transfers out of Level 3
$ 2 
$ 0 
$ 2 
$ 0 
Power
 
 
 
 
Derivative [Line Items]
 
 
 
 
Assets Transfers out of Level 3
0 
(1)
 
 
Union Electric Company |
Fuel Oils
 
 
 
 
Derivative [Line Items]
 
 
 
 
Assets Transfers out of Level 3
2 
0 
2 
0 
Union Electric Company |
Power
 
 
 
 
Derivative [Line Items]
 
 
 
 
Assets Transfers out of Level 3
0 
(1)
 
 
Ameren Illinois Company |
Fuel Oils
 
 
 
 
Derivative [Line Items]
 
 
 
 
Assets Transfers out of Level 3
0 
0 
0 
0 
Ameren Illinois Company |
Power
 
 
 
 
Derivative [Line Items]
 
 
 
 
Assets Transfers out of Level 3
$ 0 
$ 0 
 
 
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
Jun. 30, 2015
Dec. 31, 2014
Fair Value
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Long-term debt (including current portion)
$ 6,919 1
$ 7,135 1
Preferred stock
122 1
122 1
Fair Value |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Long-term debt (including current portion)
4,492 
4,518 
Preferred stock
73 
73 
Fair Value |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Long-term debt (including current portion)
2,427 
2,517 
Preferred stock
49 
49 
Carrying Amount
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Long-term debt (including current portion)
6,376 1
6,240 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)
4,135 
3,999 
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)
2,241 
2,241 
Preferred stock
$ 62 
$ 62 
Related Party Transactions Narrative (Details) (Ameren Illinois Company, Ameren Illinois Power Supply Agreements with Ameren Missouri)
6 Months Ended
Jun. 30, 2015
MWh
Ameren Illinois Company |
Ameren Illinois Power Supply Agreements with Ameren Missouri
 
Related Party Transaction [Line Items]
 
Long-term Contract for Purchase of Electric Power, Related Party Contract, Fixed Power
667,000 
Long-term Contract for Purchase of Electric Power, Related Party Contract, Fixed Power, Rate
36 
Commitments And Contingencies (Callaway Energy Center) (Detail) (USD $)
6 Months Ended
Jun. 30, 2015
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
128,000,000 
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
4,500,000.0 
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
128,000,000 
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
128,000,000 3
Property Damage
 
Commitments And Contingencies [Line Items]
 
Maximum Coverages
3,250,000,000 
Maximum Assessments for Single Incidents
27,000,000 
Property Damage - Nuclear Electric Insurance Ltd
 
Commitments And Contingencies [Line Items]
 
Maximum Coverages
2,750,000,000 4
Maximum Assessments for Single Incidents
27,000,000 5
Property Damage European Mutual Association for Nuclear Insurance
 
Commitments And Contingencies [Line Items]
 
Maximum Coverages
500,000,000 6
Replacement Power - Nuclear Electric Insurance Ltd
 
Commitments And Contingencies [Line Items]
 
Maximum Coverages
490,000,000 7
Maximum Assessments for Single Incidents
10,000,000 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
2,250,000,000 
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
$ 500,000,000 
Commitments And Contingencies (Other Obligations) (Detail) (USD $)
In Millions, unless otherwise specified
6 Months Ended
Jun. 30, 2015
MWh
Long-term Purchase Commitment [Line Items]
 
Total Other Obligations
$ 5,110 
Union Electric Company
 
Long-term Purchase Commitment [Line Items]
 
Total Other Obligations
3,247 
Ameren Illinois Company
 
Long-term Purchase Commitment [Line Items]
 
Total Other Obligations
1,822 
Amount of Megawatthours
5,526,000 
Long-term Purchase Commitment, Amount
$ 185 
Commitments And Contingencies (Environmental Matters) (Detail) (USD $)
In Millions, unless otherwise specified
Jun. 30, 2015
Minimum
 
Loss Contingencies [Line Items]
 
Estimated capital costs to comply with existing and known federal and state air emissions regulations
$ 350 
Maximum
 
Loss Contingencies [Line Items]
 
Estimated capital costs to comply with existing and known federal and state air emissions regulations
400 
Former Coal Tar Distillery |
Union Electric Company
 
Loss Contingencies [Line Items]
 
Range of possible loss, minimum
2.0 
Range of possible loss maximum
5.0 
Accrual for environmental loss contingencies
2.0 
Former Coal Ash Landfill |
Ameren Illinois Company
 
Loss Contingencies [Line Items]
 
Range of possible loss, minimum
0.5 
Range of possible loss maximum
6.0 
Accrual for environmental loss contingencies
0.5 
Manufactured Gas Plant
 
Loss Contingencies [Line Items]
 
Accrual for environmental loss contingencies
245.0 
Manufactured Gas Plant |
Ameren Illinois Company
 
Loss Contingencies [Line Items]
 
Number of remediation sites
44 
Range of possible loss, minimum
240.0 
Range of possible loss maximum
309.0 
Accrual for environmental loss contingencies
240.0 
Other Environmental |
Ameren Illinois Company
 
Loss Contingencies [Line Items]
 
Accrual for environmental loss contingencies
0.7 
Sauget Area Two |
Union Electric Company
 
Loss Contingencies [Line Items]
 
Range of possible loss, minimum
1.0 
Range of possible loss maximum
2.5 
Accrual for environmental loss contingencies
1.0 
Substation in St Charles, Missouri |
Union Electric Company
 
Loss Contingencies [Line Items]
 
Accrual for environmental loss contingencies
$ 1.0 
Commitments And Contingencies (Pumped-Storage Hydroelectric Facility Breach) (Detail) (Union Electric Company, USD $)
In Millions, unless otherwise specified
Jun. 30, 2015
Union Electric Company
 
Loss Contingencies [Line Items]
 
Insurance settlements receivable
$ 41 
Insurance Claim
$ 53 
Callaway Energy Center (Narrative) (Detail) (Nuclear Plant, USD $)
In Millions, unless otherwise specified
6 Months Ended
Jun. 30, 2015
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 (Narrative) (Detail) (USD $)
In Millions, unless otherwise specified
Jun. 30, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
Defined benefit plan, estimated future employer contributions in each of the next five years
$ 290 
Minimum
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
Defined benefit plan, estimated future employer contributions in each of the next five years
25 
Maximum
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
Defined benefit plan, estimated future employer contributions in each of the next five years
$ 115 
Retirement Benefits (Components Of Net Periodic Benefit Cost) (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 6 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Jun. 30, 2014
Pension Plan
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Service cost
$ 22 
$ 19 
$ 46 
$ 40 
Interest cost
43 
42 
87 
91 
Expected return on plan assets
(62)
(57)
(124)
(114)
Prior service cost (benefit)
 
0 
 
0 
Actuarial loss
19 
12 
37 
24 
Settlement loss
1 
0 
1 
0 
Net periodic benefit cost
23 1
16 1
47 1
41 1
Other Postretirement Benefit Plan, Defined Benefit
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Service cost
6 
4 
11 
9 
Interest cost
12 
12 
24 
25 
Expected return on plan assets
(17)
(16)
(34)
(32)
Prior service cost (benefit)
(1)
(1)
(2)
(2)
Actuarial loss
2 
(2)
3 
(3)
Net periodic benefit cost
$ 2 1
$ (3)1
$ 2 1
$ (3)1
Retirement Benefits (Summary Of Benefit Plan Costs Incurred) (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 6 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Jun. 30, 2014
Pension Plan
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Net periodic benefit cost
$ 23 1
$ 16 1
$ 47 1
$ 41 1
Pension Plan |
Union Electric Company
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Net periodic benefit cost
13 
8 
28 
25 
Pension Plan |
Ameren Illinois Company
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Net periodic benefit cost
10 
7 
19 
15 
Pension Plan |
Other Affiliated Entities and Intercompany Eliminations [Member]
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Net periodic benefit cost
 
1 
 
1 
Other Postretirement Benefit Plan, Defined Benefit
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Net periodic benefit cost
2 1
(3)1
2 1
(3)1
Other Postretirement Benefit Plan, Defined Benefit |
Union Electric Company
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Net periodic benefit cost
3 
1 
4 
2 
Other Postretirement Benefit Plan, Defined Benefit |
Ameren Illinois Company
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Net periodic benefit cost
(1)
(3)
(2)
(4)
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]
 
 
 
 
Net periodic benefit cost
 
$ (1)
 
$ (1)
Divestiture Transactions and Discontinued Operations Divestiture Transactions and Discontinued Operations (Narrative) (Details) (USD $)
In Millions, unless otherwise specified
1 Months Ended 3 Months Ended
Jun. 30, 2015
New Ameren Energy Resources Company, LLC
Dec. 31, 2014
New Ameren Energy Resources Company, LLC
Mar. 14, 2013
New Ameren Energy Resources Company, LLC
Jan. 31, 2014
Elgin, Gibson City and Grand Tower Energy Centers
Dec. 31, 2013
Elgin, Gibson City and Grand Tower Energy Centers
Jun. 30, 2015
Ameren Energy Marketing Company
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
 
 
 
 
 
 
Proceeds from Sales of Business, Affiliate and Productive Assets
 
 
 
$ 168.0 
$ 137.5 
 
Proceeds from Asset Sale Held in Escrow
 
 
 
17 
 
 
Range of possible loss maximum
25.0 
 
 
 
 
 
Notes, Loans and Financing Receivable, Net, Current
9 
12 
 
 
 
 
Collateral to be posted if credit ratings are below investment grade
19 
 
 
 
 
 
Buyer's indemnification guarantee obligation
 
 
25 
 
 
 
Loss contingency accrual
25 
 
 
 
 
 
Guarantees, Maximum Exposure
 
 
 
 
 
6 
Guarantees Outstanding
79 
 
 
 
 
 
Letters of Credit Outstanding, Amount
$ 9 
 
 
 
 
 
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 6 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Jun. 30, 2014
Discontinued Operations and Disposal Groups [Abstract]
 
 
 
 
Operating revenues
$ 0 
$ 0 
$ 0 
$ 1 
Operating benefits (expenses)
0 
(1)
3 
(3)
Operating income (loss) before income tax
0 
(1)
3 
(2)
Income tax benefit
52 
0 
49 
0 
Income (loss) from discontinued operations, net of taxes
$ 52 
$ (1)
$ 52 
$ (2)
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
Jun. 30, 2015
Dec. 31, 2014
Assets of discontinued operations
 
 
Accumulated deferred income taxes, net
$ 15 
$ 15 
Total assets of discontinued operations
15 
15 
Liabilities of discontinued operations
 
 
Accounts payable and other current obligations
2 
1 
Asset retirement obligations
30 
32 
Total liabilities of discontinued operations
$ 32 
$ 33 
Segment Information (Schedule Of Segment Reporting Information By Segment) (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 6 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Jun. 30, 2014
Dec. 31, 2014
Segment Reporting Information [Line Items]
 
 
 
 
 
Number of Reportable Segments
 
 
2 
 
 
External revenues
$ 1,401 
$ 1,419 
$ 2,957 
$ 3,013 
 
Net income (loss) attributable to Ameren Corporation from continuing operations
98 
150 
206 
247 
 
Total assets
23,152 
 
23,152 
 
22,676 
Assets of discontinued operations (Note 12)
15 
 
15 
 
15 
Union Electric Company
 
 
 
 
 
Segment Reporting Information [Line Items]
 
 
 
 
 
Number of Reportable Segments
 
 
1 
 
 
External revenues
872 
893 
1,665 
1,704 
 
Intersegment revenues
12 
7 
19 
13 
 
Net income (loss) attributable to Ameren Corporation from continuing operations
61 
126 
102 
173 
 
Total assets
13,721 
 
13,721 
 
13,541 
Ameren Illinois Company
 
 
 
 
 
Segment Reporting Information [Line Items]
 
 
 
 
 
Number of Reportable Segments
 
 
1 
 
 
External revenues
512 
518 
1,256 
1,292 
 
Intersegment revenues
1 
1 
2 
1 
 
Net income (loss) attributable to Ameren Corporation from continuing operations
31 
28 
84 
81 
 
Total assets
8,500 
 
8,500 
 
8,381 
Other
 
 
 
 
 
Segment Reporting Information [Line Items]
 
 
 
 
 
External revenues
17 
8 
36 
17 
 
Intersegment revenues
 
 
1 
1 
 
Net income (loss) attributable to Ameren Corporation from continuing operations
6 
(4)
20 
(7)
 
Total assets
1,036 
 
1,036 
 
942 
Intersegment Eliminations
 
 
 
 
 
Segment Reporting Information [Line Items]
 
 
 
 
 
Intersegment revenues
(13)
(8)
(22)
(15)
 
Total assets
(120)
 
(120)
 
(203)
Consolidated, Continuing Operations
 
 
 
 
 
Segment Reporting Information [Line Items]
 
 
 
 
 
External revenues
1,401 
1,419 
2,957 
3,013 
 
Net income (loss) attributable to Ameren Corporation from continuing operations
98 
150 
206 
247 
 
Total assets
$ 23,137 1
 
$ 23,137 1
 
$ 22,661 1