UNION ELECTRIC CO, 10-Q filed on 11/3/2017
Quarterly Report
Document and Entity Information
9 Months Ended
Sep. 30, 2017
Oct. 31, 2017
Entity Information [Line Items]
 
 
Document Type
10-Q 
 
Amendment Flag
false 
 
Document Period End Date
Sep. 30, 2017 
 
Document Fiscal Year Focus
2017 
 
Document Fiscal Period Focus
Q3 
 
Trading Symbol
AEE 
 
Entity Registrant Name
AMEREN CORP 
 
Entity Central Index Key
0001002910 
 
Current Fiscal Year End Date
--12-31 
 
Entity Filer Category
Large Accelerated Filer 
 
Entity Common Stock, Shares Outstanding
 
242,634,798 
Union Electric Company
 
 
Entity Information [Line Items]
 
 
Document Type
10-Q 
 
Amendment Flag
false 
 
Document Period End Date
Sep. 30, 2017 
 
Document Fiscal Year Focus
2017 
 
Document Fiscal Period Focus
Q3 
 
Entity Registrant Name
UNION ELECTRIC CO 
 
Entity Central Index Key
0000100826 
 
Current Fiscal Year End Date
--12-31 
 
Entity Filer Category
Non-accelerated Filer 
 
Entity Common Stock, Shares Outstanding
 
102,123,834 
Ameren Illinois Company
 
 
Entity Information [Line Items]
 
 
Document Type
10-Q 
 
Amendment Flag
false 
 
Document Period End Date
Sep. 30, 2017 
 
Document Fiscal Year Focus
2017 
 
Document Fiscal Period Focus
Q3 
 
Entity Registrant Name
AMEREN ILLINOIS CO 
 
Entity Central Index Key
0000018654 
 
Current Fiscal Year End Date
--12-31 
 
Entity Filer Category
Non-accelerated Filer 
 
Entity Common Stock, Shares Outstanding
 
25,452,373 
Consolidated Statement of Income (Loss) (USD $)
In Millions, except Per Share data, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Operating Revenues:
 
 
 
 
Electric
$ 1,594 
$ 1,725 
$ 4,183 
$ 4,101 
Gas
129 
134 
592 
619 
Total operating revenues
1,723 
1,859 
4,775 
4,720 
Operating Expenses:
 
 
 
 
Fuel
199 
205 
594 
574 
Purchased power
162 
178 
491 
451 
Gas purchased for resale
25 
34 
196 
227 
Other operations and maintenance
402 
411 
1,229 
1,246 
Depreciation and amortization
225 
211 
668 
628 
Taxes other than income taxes
129 
129 
364 
358 
Total operating expenses
1,142 
1,168 
3,542 
3,484 
Operating Income
581 
691 
1,233 
1,236 
Other Income and Expenses:
 
 
 
 
Miscellaneous income
13 1
18 1
42 1
54 1
Miscellaneous expense
2 1
8 1
16 1
21 1
Total other income (expense)
11 
10 
26 
33 
Interest Charges
97 
97 
295 
287 
Income Before Income Taxes
495 
604 
964 
982 
Income Taxes
205 
233 
376 
356 
Net income
290 
371 
588 
626 
Pension and other postretirement benefit plan activity, net of income taxes (benefit)
0 
(1)
2 
1 
Comprehensive Income
288 
368 
585 
622 
Less: Net Income Attributable to Noncontrolling Interests
2 
2 
5 
5 
Net Income Attributable to Ameren Common Shareholders
288 
369 
583 
621 
Earnings Per Share, Basic and Diluted [Abstract]
 
 
 
 
Earnings Per Share, Basic
$ 1.19 
$ 1.52 
$ 2.40 
$ 2.56 
Earnings Per Share, Diluted
$ 1.18 
$ 1.52 
$ 2.39 
$ 2.56 
Dividends per Common Share
$ 0.44 
$ 0.425 
$ 1.32 
$ 1.275 
Average Common Shares Outstanding - Basic
242.6 
242.6 
242.6 
242.6 
Average Common Shares Outstanding - Diluted
244.7 
242.9 
244.0 
243.0 
Union Electric Company
 
 
 
 
Operating Revenues:
 
 
 
 
Electric
1,098 
1,144 
2,757 
2,682 
Gas
17 
20 
83 
90 
Other Revenue, Net
0 
1 
0 
1 
Total operating revenues
1,115 
1,165 
2,840 
2,773 
Operating Expenses:
 
 
 
 
Fuel
199 
205 
594 
574 
Purchased power
42 
77 
201 
169 
Gas purchased for resale
4 
6 
29 
33 
Other operations and maintenance
224 
220 
655 
670 
Depreciation and amortization
134 
130 
399 
384 
Taxes other than income taxes
95 
96 
255 
252 
Total operating expenses
698 
734 
2,133 
2,082 
Operating Income
417 
431 
707 
691 
Other Income and Expenses:
 
 
 
 
Miscellaneous income
13 
14 
36 
38 
Miscellaneous expense
2 
2 
6 
6 
Total other income (expense)
11 
12 
30 
32 
Interest Charges
50 
53 
157 
158 
Income Before Income Taxes
378 
390 
580 
565 
Income Taxes
143 
148 
218 
215 
Net income
235 
242 
362 
350 
Other Comprehensive Income
0 
0 
0 
0 
Comprehensive Income
235 
242 
362 
350 
Earnings Per Share, Basic and Diluted [Abstract]
 
 
 
 
Preferred Stock Dividends
1 
1 
3 
3 
Net Income Available to Common Stockholder
234 
241 
359 
347 
Ameren Illinois Company
 
 
 
 
Operating Revenues:
 
 
 
 
Electric
463 
562 
1,343 
1,365 
Gas
112 
114 
510 
530 
Other Revenue, Net
0 
0 
1 
0 
Total operating revenues
575 
676 
1,854 
1,895 
Operating Expenses:
 
 
 
 
Purchased power
124 
110 
312 
304 
Gas purchased for resale
21 
28 
167 
194 
Other operations and maintenance
183 
198 
590 
592 
Depreciation and amortization
86 
80 
254 
237 
Taxes other than income taxes
33 
30 
101 
98 
Total operating expenses
447 
446 
1,424 
1,425 
Operating Income
128 
230 
430 
470 
Other Income and Expenses:
 
 
 
 
Miscellaneous income
1 
4 
7 
15 
Miscellaneous expense
0 
3 
8 
11 
Total other income (expense)
1 
1 
(1)
4 
Interest Charges
36 
35 
109 
105 
Income Before Income Taxes
93 
196 
320 
369 
Income Taxes
38 
77 
127 
144 
Net income
55 
119 
193 
225 
Pension and other postretirement benefit plan activity, net of income taxes (benefit)
0 
(1)
0 
(3)
Comprehensive Income
55 
118 
193 
222 
Earnings Per Share, Basic and Diluted [Abstract]
 
 
 
 
Preferred Stock Dividends
0 
0 
2 
2 
Net Income Available to Common Stockholder
$ 55 
$ 119 
$ 191 
$ 223 
Consolidated Statement of Income (Loss) (Parenthetical) (USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Pension and other postretirement benefit plan activity, tax expense (benefit)
$ 0 
$ 0 
$ 1 
$ 4 
Ameren Illinois Company
 
 
 
 
Pension and other postretirement benefit plan activity, tax expense (benefit)
$ 0 
$ (1)
$ 0 
$ (2)
Consolidated Statement of Comprehensive Income (Loss) (USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
 
 
 
 
Net income
$ 290 
$ 371 
$ 588 
$ 626 
Other Comprehensive Income (Loss), Net of Taxes
 
 
 
 
Pension and other postretirement benefit plan activity, net of income taxes (benefit)
0 
(1)
2 
1 
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest
290 
370 
590 
627 
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest
2 
2 
5 
5 
Comprehensive Income Attributable to Ameren Common Shareholders
$ 288 
$ 368 
$ 585 
$ 622 
Consolidated Statement of Comprehensive Income (Loss) Consolidated Statement of Income (Parenthetical) (USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
 
 
 
 
Pension and other postretirement benefit plan activity, tax expense (benefit)
$ 0 
$ 0 
$ 1 
$ 4 
Consolidated Balance Sheet (USD $)
In Millions, unless otherwise specified
Sep. 30, 2017
Dec. 31, 2016
Current Assets:
 
 
Cash and cash equivalents
$ 9 
$ 9 
Accounts receivable - trade (less allowance for doubtful accounts)
507 
437 
Unbilled revenue
262 
295 
Miscellaneous accounts and notes receivable
85 
63 
Inventories
547 
527 
Current regulatory assets
75 
149 
Other current assets
96 
113 
Total current assets
1,581 
1,593 
Property, Plant, and Equipment, Net
20,906 
20,113 
Investments and Other Assets:
 
 
Nuclear decommissioning trust fund
672 
607 
Goodwill
411 
411 
Regulatory assets
1,509 
1,437 
Other assets
538 
538 
Total investments and other assets
3,130 
2,993 
TOTAL ASSETS
25,617 
24,699 
Current Liabilities:
 
 
Current maturities of long-term debt
777 
681 
Short-term Debt
446 
558 
Accounts and wages payable
548 
805 
Taxes accrued
159 
46 
Interest accrued
106 
93 
Customer deposits
108 
107 
Current regulatory liabilities
119 
110 
Other current liabilities
318 
274 
Total current liabilities
2,581 
2,674 
Long-term Debt, Net
6,922 
6,595 
Deferred Credits and Other Liabilities:
 
 
Accumulated deferred income taxes, net
4,721 
4,264 
Accumulated deferred investment tax credits
50 
55 
Regulatory liabilities
2,045 
1,985 
Asset retirement obligations
631 
635 
Pension and other postretirement benefits
711 
769 
Other deferred credits and liabilities
469 
477 
Total deferred credits and other liabilities
8,627 
8,185 
Commitments and Contingencies
   
   
Stockholders' Equity:
 
 
Common Stock
2 
2 
Other paid-in capital
5,534 
5,556 
Retained earnings
1,830 
1,568 
Accumulated other comprehensive loss
(21)
(23)
Stockholder's equity
7,345 
7,103 
Noncontrolling Interest
142 
142 
Total equity
7,487 
7,245 
TOTAL LIABILITIES AND EQUITY
25,617 
24,699 
Union Electric Company
 
 
Current Assets:
 
 
Cash and cash equivalents
0 
0 
Advances to money pool
18 
161 
Accounts receivable - trade (less allowance for doubtful accounts)
274 
187 
Accounts receivable - affiliates
14 
12 
Unbilled revenue
151 
154 
Miscellaneous accounts and notes receivable
45 
14 
Inventories
396 
392 
Current regulatory assets
23 
35 
Other current assets
43 
49 
Total current assets
964 
1,004 
Property, Plant, and Equipment, Net
11,538 
11,478 
Investments and Other Assets:
 
 
Nuclear decommissioning trust fund
672 
607 
Regulatory assets
576 
619 
Other assets
318 
327 
Total investments and other assets
1,566 
1,553 
TOTAL ASSETS
14,068 
14,035 
Current Liabilities:
 
 
Current maturities of long-term debt
383 
431 
Short-term Debt
0 
0 
Accounts and wages payable
226 
444 
Accounts payable - affiliates
102 
68 
Taxes accrued
148 
30 
Interest accrued
61 
54 
Current regulatory liabilities
18 
12 
Other current liabilities
118 
123 
Total current liabilities
1,056 
1,162 
Long-term Debt, Net
3,584 
3,563 
Deferred Credits and Other Liabilities:
 
 
Accumulated deferred income taxes, net
3,073 
3,013 
Accumulated deferred investment tax credits
49 
53 
Regulatory liabilities
1,275 
1,215 
Asset retirement obligations
627 
629 
Pension and other postretirement benefits
274 
291 
Other deferred credits and liabilities
13 
19 
Total deferred credits and other liabilities
5,311 
5,220 
Commitments and Contingencies
   
   
Stockholders' Equity:
 
 
Common Stock
511 
511 
Other paid-in capital
1,828 
1,828 
Preferred stock
80 
80 
Retained earnings
1,698 
1,671 
Stockholder's equity
4,117 
4,090 
TOTAL LIABILITIES AND EQUITY
14,068 
14,035 
Ameren Illinois Company
 
 
Current Assets:
 
 
Cash and cash equivalents
0 
0 
Accounts receivable - trade (less allowance for doubtful accounts)
219 
242 
Accounts receivable - affiliates
21 
10 
Unbilled revenue
111 
141 
Miscellaneous accounts and notes receivable
31 
22 
Inventories
151 
135 
Current regulatory assets
51 
108 
Other current assets
18 
25 
Total current assets
602 
683 
Property, Plant, and Equipment, Net
7,987 
7,469 
Investments and Other Assets:
 
 
Goodwill
411 
411 
Regulatory assets
921 
816 
Other assets
101 
95 
Total investments and other assets
1,433 
1,322 
TOTAL ASSETS
10,022 
9,474 
Current Liabilities:
 
 
Current maturities of long-term debt
394 
250 
Short-term Debt
169 
51 
Borrowings from money pool
11 
0 
Accounts and wages payable
247 
264 
Accounts payable - affiliates
50 
63 
Taxes accrued
8 
16 
Interest accrued
37 
33 
Customer deposits
69 
69 
Current environmental remediation
43 
38 
Current regulatory liabilities
85 
78 
Other current liabilities
153 
109 
Total current liabilities
1,266 
971 
Long-term Debt, Net
2,196 
2,338 
Deferred Credits and Other Liabilities:
 
 
Accumulated deferred income taxes, net
1,874 
1,631 
Accumulated deferred investment tax credits
1 
2 
Regulatory liabilities
766 
768 
Pension and other postretirement benefits
322 
346 
Environmental remediation
143 
162 
Other deferred credits and liabilities
229 
222 
Total deferred credits and other liabilities
3,335 
3,131 
Commitments and Contingencies
   
   
Stockholders' Equity:
 
 
Common Stock
0 
0 
Other paid-in capital
2,005 
2,005 
Preferred stock
62 
62 
Retained earnings
1,158 
967 
Stockholder's equity
3,225 
3,034 
TOTAL LIABILITIES AND EQUITY
$ 10,022 
$ 9,474 
Consolidated Balance Sheet (Parenthetical) (USD $)
In Millions, except Per Share data, unless otherwise specified
Sep. 30, 2017
Dec. 31, 2016
Accounts receivable - trade allowance for doubtful accounts
$ 20 
$ 19 
Common stock, par value
$ 0.01 
$ 0.01 
Common stock, shares authorized
400.0 
400.0 
Common stock, shares outstanding
242.6 
242.6 
Union Electric Company
 
 
Accounts receivable - trade allowance for doubtful accounts
8 
7 
Common stock, par value
$ 5 
$ 5 
Common stock, shares authorized
150.0 
150.0 
Common stock, shares outstanding
102.1 
102.1 
Ameren Illinois Company
 
 
Accounts receivable - trade allowance for doubtful accounts
$ 12 
$ 12 
Common stock, no par value
$ 0 
$ 0 
Common stock, shares authorized
45.0 
45.0 
Common stock, shares outstanding
25.5 
25.5 
Consolidated Statement of Cash Flows (USD $)
In Millions, unless otherwise specified
9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Cash Flows From Operating Activities:
 
 
Net income
$ 588 
$ 626 
Adjustments to reconcile net income to net cash provided by operating activities:
 
 
Depreciation and amortization
653 
625 
Amortization of nuclear fuel
71 
63 
Amortization of debt issuance costs and premium/discounts
16 
17 
Deferred income taxes and investment tax credits, net
366 
364 
Allowance for equity funds used during construction
(16)1
(20)1
Share-based compensation costs
12 
17 
Other
(7)
(9)
Changes in assets and liabilities:
 
 
Receivables
(59)
(134)
Inventories
(20)
(13)
Accounts and wages payable
(183)
(196)
Taxes accrued
138 
119 
Regulatory assets and liabilities
89 
146 
Assets, other
14 
9 
Liabilities, other
12 
(29)
Pension and other postretirement benefits
(31)
(26)
Net cash provided by operating activities
1,643 
1,559 
Cash Flows From Investing Activities:
 
 
Capital expenditures
(1,523)
(1,496)
Nuclear fuel expenditures
(52)
(41)
Purchases of securities - nuclear decommissioning trust fund
(248)
(310)
Sales and maturities of securities - nuclear decommissioning trust fund
235 
297 
Other
3 
(1)
Net cash used in investing activities
(1,585)
(1,551)
Cash Flows From Financing Activities:
 
 
Dividends on common stock
(320)
(309)
Dividends paid to noncontrolling interest holders
(5)
(5)
Short-term debt, net
(112)
307 
Maturities of Long-term Debt
(425)
(389)
Proceeds from Issuance of Long-term Debt
849 
149 
Share-based payments
(39)
(32)
Debt issuance costs
(5)
(1)
Other
(1)
(2)
Net cash used in financing activities
(58)
(282)
Net change in cash and cash equivalents
0 
(274)
Cash and cash equivalents at beginning of period
9 
292 
Cash and cash equivalents at end of period
9 
18 
Union Electric Company
 
 
Cash Flows From Operating Activities:
 
 
Net income
362 
350 
Adjustments to reconcile net income to net cash provided by operating activities:
 
 
Depreciation and amortization
384 
381 
Amortization of nuclear fuel
71 
63 
Amortization of debt issuance costs and premium/discounts
5 
5 
Deferred income taxes and investment tax credits, net
55 
159 
Allowance for equity funds used during construction
(15)
(16)
Other
4 
0 
Changes in assets and liabilities:
 
 
Receivables
(117)
(95)
Inventories
(3)
(5)
Accounts and wages payable
(151)
(176)
Taxes accrued
160 
165 
Regulatory assets and liabilities
48 
60 
Assets, other
19 
(8)
Liabilities, other
4 
13 
Pension and other postretirement benefits
(7)
(8)
Net cash provided by operating activities
819 
888 
Cash Flows From Investing Activities:
 
 
Capital expenditures
(533)
(500)
Nuclear fuel expenditures
(52)
(41)
Purchases of securities - nuclear decommissioning trust fund
(248)
(310)
Sales and maturities of securities - nuclear decommissioning trust fund
235 
297 
Money pool advances, net
143 
(165)
Other
0 
(5)
Net cash used in investing activities
(455)
(724)
Cash Flows From Financing Activities:
 
 
Dividends on common stock
(332)
(285)
Dividends on preferred stock
(3)
(3)
Maturities of Long-term Debt
(425)
(260)
Proceeds from Issuance of Long-term Debt
399 
149 
Capital contribution from parent
0 
38 
Debt issuance costs
(3)
(1)
Net cash used in financing activities
(364)
(362)
Net change in cash and cash equivalents
0 
(198)
Cash and cash equivalents at beginning of period
0 
199 
Cash and cash equivalents at end of period
0 
1 
Ameren Illinois Company
 
 
Cash Flows From Operating Activities:
 
 
Net income
193 
225 
Adjustments to reconcile net income to net cash provided by operating activities:
 
 
Depreciation and amortization
254 
236 
Amortization of debt issuance costs and premium/discounts
10 
11 
Deferred income taxes and investment tax credits, net
161 
141 
Allowance for equity funds used during construction
(1)
(4)
Other
(1)
(8)
Changes in assets and liabilities:
 
 
Receivables
59 
(36)
Inventories
(17)
(8)
Accounts and wages payable
(24)
(17)
Taxes accrued
(22)
5 
Regulatory assets and liabilities
45 
75 
Assets, other
(9)
11 
Liabilities, other
(2)
6 
Pension and other postretirement benefits
(19)
(14)
Net cash provided by operating activities
628 
627 
Cash Flows From Investing Activities:
 
 
Capital expenditures
(760)
(683)
Other
6 
4 
Net cash used in investing activities
(754)
(679)
Cash Flows From Financing Activities:
 
 
Dividends on common stock
0 
(95)
Dividends on preferred stock
(2)
(2)
Short-term debt, net
118 
157 
Money pool borrowings, net
11 
54 
Maturities of Long-term Debt
0 
(129)
Other
(1)
(1)
Net cash used in financing activities
126 
(16)
Net change in cash and cash equivalents
0 
(68)
Cash and cash equivalents at beginning of period
0 
71 
Cash and cash equivalents at end of period
$ 0 
$ 3 
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 whose primary assets are its equity interests in its subsidiaries. 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, Ameren Missouri, Ameren Illinois, and ATXI, are described below. Ameren also has other subsidiaries that conduct other activities, such as the provision of shared services. Ameren evaluates competitive electric transmission investment opportunities outside of MISO as they arise.
•
Union Electric Company, doing business as Ameren Missouri, operates a rate-regulated electric generation, transmission, and distribution business and a rate-regulated natural gas distribution business in Missouri.
•
Ameren Illinois Company, doing business as Ameren Illinois, operates rate-regulated electric transmission, electric distribution, and natural gas distribution businesses in Illinois.
•
ATXI 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’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. All tabular dollar amounts are in millions, unless otherwise indicated. Also see the Glossary of Terms and Abbreviations at the front of this report and in the Form 10-K.
As of September 30, 2017 and December 31, 2016, Ameren had unconsolidated variable interests as a limited partner in various equity method investments, totaling $14 million and $9 million, respectively, included in “Other assets” on Ameren’s consolidated balance sheet. Ameren is not the primary beneficiary of these investments because it does not have the power to direct matters that most significantly impact the activities of these variable interest entities. As of September 30, 2017, the maximum exposure to loss related to these variable interests is limited to the investment in these partnerships of $14 million plus associated outstanding funding commitments of $23 million.
Our accounting policies conform to GAAP. Our financial statements reflect all adjustments (which include normal, recurring adjustments) that are necessary, in our opinion, for a fair statement of our results. The preparation of financial statements in conformity with GAAP requires management to make certain estimates and assumptions. Such estimates and assumptions affect reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the dates of financial statements, and the reported amounts of revenues and expenses during the reported periods. Actual results could differ from those estimates. The results of operations of an interim period may not give a true indication of results that may be expected for a full year. See Note 2 – Rate and Regulatory Matters for information regarding the 2017 change in Ameren Illinois' method used to recognize interim period revenue in connection with the revenue decoupling provisions of the FEJA. These financial statements should be read in conjunction with the financial statements and the notes thereto included in the Form 10-K.
Discontinued operations were immaterial to all periods presented in Ameren’s financial statements. As such, the “Assets of discontinued operations” and “Liabilities of discontinued operations” included on the December 31, 2016 balance sheet have been reclassified in this report to “Other current assets” and “Other current liabilities,” respectively. See Note 1 – Summary of Significant Accounting Policies under Part II, Item 8, of the Form 10-K for additional information.
Asset Retirement Obligations
The following table provides a reconciliation of the beginning and ending carrying amount of AROs for the nine months ended September 30, 2017:
 
Ameren
Missouri
 
Ameren
Illinois(a)
 
Ameren
 
Balance at December 31, 2016
$
644

(b) 
$
6

 
$
650

(b) 
Liabilities settled
(4
)
 
(1
)
 
(5
)
 
Accretion(c)
20

 
(d)

 
20

 
Change in estimates(e)
(18
)
 
(1
)
 
(19
)
 
Balance at September 30, 2017
$
642

(b) 
$
4

 
$
646

(b) 
(a)
Included in “Other deferred credits and liabilities” on the balance sheet.
(b)
Balance included $15 million in “Other current liabilities” on the balance sheet as of both December 31, 2016 and September 30, 2017, respectively.
(c)
Accretion expense was recorded as a decrease to regulatory liabilities.
(d)
Less than $1 million.
(e)
Ameren Missouri changed its fair value estimate primarily due to an extension of the remediation period of certain CCR storage facilities, an update to the decommissioning of the Callaway energy center to reflect the cost study and funding analysis filed with the MoPSC in 2017, and an increase in the discount rate assumption.
Share-based Compensation
A summary of nonvested performance share units at September 30, 2017, and changes during the nine months ended September 30, 2017, under the 2014 Incentive Plan are presented below:
 
Performance Share Units
 
Share Units
 
Weighted-average Fair Value per Share Unit
Nonvested at January 1, 2017
1,059,639

 
$
48.04

Granted(a)
500,943

 
59.16

Forfeitures
(48,661
)
 
52.54

Vested(b)
(27,446
)
 
52.88

Nonvested at September 30, 2017
1,484,475

 
$
51.55

(a)
Performance share units granted to certain executive and nonexecutive officers and other eligible employees under the 2014 Incentive Plan.
(b)
Performance share units vested due to the attainment of retirement eligibility by certain employees. Actual shares issued for retirement-eligible employees vary depending on actual performance over the three-year measurement period.
The fair value of each performance share unit awarded in 2017 under the 2014 Incentive Plan was determined to be $59.16, which was based on Ameren’s closing common share price of $52.46 at December 31, 2016, and lattice simulations. Lattice simulations are used to estimate expected share payout based on Ameren’s total shareholder return for a three-year performance period beginning January 1, 2017, relative to the designated peer group. The simulations can produce a greater fair value for the performance share unit than the December 31 applicable closing common share price because they include the weighted payout scenarios in which an increase in the share price has occurred. The significant assumptions used to calculate fair value also included a three-year risk-free rate of 1.47%, volatility of 15% to 21% for the peer group, and Ameren’s attainment of a three-year average earnings per share threshold during the performance period.
Operating Revenue
The Ameren Companies record operating revenue for electric or natural gas service when it is delivered to customers. We accrue an estimate of electric and natural gas revenues for service rendered but unbilled at the end of each accounting period. For certain regulatory recovery mechanisms qualifying as alternative revenue programs, such as revenue requirement reconciliations, the Ameren Companies recognize revenues that have been authorized for rate recovery, are objectively determinable and probable of recovery, and are expected to be collected from customers within two years from the end of the year.
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 – Natural 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 therefore are not included in Ameren Illinois’ revenues and expenses. The following table presents excise taxes recorded in “Operating Revenues – Electric,” “Operating Revenues – Natural gas” and “Operating Expenses – Taxes other than income taxes” for the three and nine months ended September 30, 2017 and 2016:
 
Three Months
 
 
Nine Months
 
2017
 
2016
 
 
2017
 
2016
Ameren Missouri
$
51

 
$
52

 
 
$
122

 
$
122

Ameren Illinois
10

 
9

 
 
40

 
40

Ameren
$
61

 
$
61

 
 
$
162

 
$
162


Earnings Per Share
Basic earnings per share is computed by dividing “Net Income Attributable to Ameren Common Shareholders” by the weighted-average number of common shares outstanding during the period. Earnings per diluted share is computed by dividing “Net Income Attributable to Ameren Common Shareholders” by the weighted-average number of diluted common shares outstanding during the period. Earnings per diluted share reflects the dilution that would occur if certain stock-based performance share units were settled. The number of performance share units assumed to be settled was 2.1 million and 1.4 million in the three and nine months ended September 30, 2017, respectively, and 0.3 million and 0.4 million, respectively, in the year-ago periods. There were no potentially dilutive securities excluded from the earnings per diluted share calculations for the three and nine months ended September 30, 2017 and 2016.
Income Taxes
In July 2017, Illinois enacted a law that increased the state's corporate income tax rate from 7.75% to 9.5% as of July 1, 2017. The law made the increase in the state’s corporate income tax rate, which was previously scheduled to decrease to 7.3% in 2025, permanent. In July 2017, Ameren recorded an expense of $14 million at Ameren (parent) due to the revaluation of accumulated deferred taxes and the estimated state apportionment of such taxes. Beyond this expense, Ameren does not expect this tax increase to have a material impact on its consolidated net income prospectively. The tax increase is not expected to materially impact the earnings of the Ameren Illinois Electric Distribution, the Ameren Transmission, or the Ameren Illinois Transmission segments, since these businesses operate under formula ratemaking frameworks. The tax increase is expected to unfavorably affect 2017 net income of the Ameren Illinois Natural Gas segment by less than $1 million. In addition, in the third quarter of 2017, Ameren’s and Ameren Illinois’ accumulated deferred tax balances were revalued using the state’s new corporate income tax rate, which resulted in a net increase to the liability balances of $97 million and $79 million, respectively. These increased liabilities were offset by a regulatory asset, as well as income tax expense, as discussed above.
Accounting and Reporting Developments
Below is a summary of updates related to our adoption of recently issued authoritative accounting standards. See Note 1 – Summary of Significant Accounting Policies under Part II, Item 8, of the Form 10-K for additional information about recently issued authoritative accounting standards relating to leases, financial instruments, and restricted cash.
Revenue from Contracts with Customers
In May 2014, the FASB issued authoritative guidance that changes the criteria for recognizing revenue from a contract with a customer. The underlying principle of the guidance is that an entity will recognize revenue for the transfer of promised goods or services to customers at an amount that the entity expects to be entitled to in exchange for those goods or services. The guidance 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, as well as separate presentation of alternative revenue programs on the income statement. Entities can apply the guidance to each reporting period presented (the full retrospective method) or by recording a cumulative effect adjustment to retained earnings in the period of initial adoption (the modified retrospective method).
We have substantially completed the evaluation of our contracts and do not expect material changes to the amount or timing of revenue recognition. We will finalize our contract assessments by the end of 2017. We will apply the guidance using the full retrospective method and include disaggregated revenue disclosures by segment and customer class in the combined notes to the financial statements in the first quarter of 2018.
Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost
In March 2017, the FASB issued authoritative guidance that requires an entity to retrospectively report the service cost component of net benefit cost in the same line item(s) as other compensation costs arising from services rendered by employees during the period and to present the other components of net benefit cost in the income statement separately from the service cost component and outside of operating income. The guidance also requires that an entity only capitalize the service cost component as part of an asset, such as inventory or property, plant, and equipment, on a prospective basis. Previously, all of the net benefit cost components were eligible for capitalization. This change in the capitalization of net benefit costs will not affect our ability to continue to obtain recovery of net benefit costs through customer rates. See Note 11 – Retirement Benefits for the components of net benefit cost. This guidance will be effective for the Ameren Companies in the first quarter of 2018. We are currently assessing the impacts of this guidance on our results of operations, financial position, and disclosures.
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
March 2017 Electric Rate Order
In March 2017, the MoPSC issued an order approving a unanimous stipulation and agreement in Ameren Missouri’s July 2016 regulatory rate review. The order resulted in a $3.4 billion revenue requirement, which is a $92 million increase in Ameren Missouri’s annual revenue requirement for electric service, compared to its prior revenue requirement established in the MoPSC's April 2015 electric rate order. The new rates, base level of expenses, and amortizations became effective on April 1, 2017.
The order authorized the continued use of the FAC and the regulatory tracking mechanisms for pension and postretirement benefits, uncertain income tax positions, and renewable energy standards that the MoPSC authorized in earlier electric rate orders. These regulatory tracking mechanisms provide for a base level of expense to be reflected in Ameren Missouri’s base electric rates with differences in the actual expenses incurred recorded as a regulatory asset or liability. Excluding cost reductions associated with reduced sales volumes, the base level of net energy costs decreased by $54 million from the base level established in the MoPSC's April 2015 electric rate order. Changes in amortizations and the base level of expenses for the other regulatory tracking mechanisms, including extending the amortization period of certain regulatory assets, reduced expenses by $26 million from the base levels established in the MoPSC's April 2015 electric rate order.
ATXI’s Mark Twain Project
The Mark Twain project is a MISO-approved transmission line to be located in northeast Missouri. In the third quarter of 2017, ATXI finalized an alternative project route and reached agreements with a cooperative electric company in northeast Missouri and Ameren Missouri to locate nearly all of the Mark Twain project on existing transmission line corridors. It also received assents for road crossings from the five affected counties in northeast Missouri. ATXI had previously filed suit in the circuit courts to obtain assents for the original project route. ATXI has since withdrawn one of the lawsuits. The other lawsuits remain pending but have been stayed until the first quarter of 2018. In September 2017, ATXI filed for a certificate of convenience and necessity with the MoPSC and anticipates a decision from the MoPSC in the first half of 2018. ATXI plans to complete the project in December 2019; however, delays in obtaining approval from the MoPSC could delay completion.
Illinois
IEIMA & FEJA
Ameren Illinois’ electric distribution service rates are subject to an annual revenue requirement reconciliation to its actual recoverable costs and allowed return on equity under a formula ratemaking process effective through 2022. This formula ratemaking framework qualifies as an alternative revenue program under GAAP. Each year, Ameren Illinois records a regulatory asset or a regulatory liability and a corresponding increase or decrease to operating revenues for any differences between the revenue requirement reflected in customer rates for that year and its estimate of the probable increase or decrease in the revenue requirement expected to ultimately be approved by the ICC based on that year's actual recoverable costs incurred and investment return. As of September 30, 2017, Ameren Illinois had recorded regulatory assets of $24 million to reflect its 2016 revenue requirement reconciliation adjustment, which was included in the April 2017 formula rate update discussed below, and $16 million for the approved 2015 revenue requirement reconciliation adjustment, each with interest. As of September 30, 2017, Ameren Illinois had recorded a regulatory liability of $1 million to reflect the difference between Ameren Illinois’ estimate of its 2017 revenue requirement and the revenue requirement reflected in customer rates, including interest.
In April 2017, Ameren Illinois filed with the ICC its annual electric distribution service formula rate update to establish the revenue requirement used for 2018 rates. In June 2017, the ICC staff submitted its calculation of the revenue requirement, which Ameren Illinois supported in its revised July 2017 filing, and recommended a decrease to the electric distribution service revenue requirement. Pending ICC approval, this update filing will result in a $17 million decrease in Ameren Illinois’ electric distribution service revenue requirement beginning in January 2018. This update reflects an increase to the annual formula rate based on 2016 actual costs and expected net plant additions for 2017, as well as an increase to include the 2016 revenue requirement reconciliation adjustment. The increases in the update filing are more than offset by a decrease for the conclusion of the 2015 revenue requirement reconciliation adjustment, which will be fully collected from customers in 2017, consistent with the ICC’s December 2016 annual update filing order. In November 2017, an administrative law judge issued a proposed order that was consistent with Ameren Illinois’ revised July 2017 filing. An ICC decision regarding the revenue requirement to be used for customer rates in 2018 is expected by December 2017.
The FEJA revised certain portions of the IEIMA, including extending the IEIMA formula ratemaking process through 2022 and clarifying that a common equity ratio of up to, and including, 50% is prudent. Beginning in 2017, the FEJA provides that Ameren Illinois will recover, within the following two years, its electric distribution revenue requirement for a given year, independent of actual sales volumes. Prior to the FEJA, Ameren Illinois’ interim period revenue recognition was volume-based, as revenues were affected by the timing of sales volumes due to seasonal rates and changes in volumes resulting from, among other things, weather and energy efficiency. This previous revenue recognition method resulted in more revenues during the third quarter and less revenues during the other quarters of each year. Beginning in 2017, in connection with the decoupling provisions of the FEJA, Ameren Illinois changed its method used to recognize interim period revenue. Ameren Illinois now recognizes revenue consistent with the timing of actual incurred electric distribution recoverable costs and recognizes revenue associated with the expected return on its rate base ratably over the year. Ameren Illinois recognized a reduction to electric revenue to reflect the difference between the estimate of its revenue requirement and the revenue requirement reflected in customer rates of $76 million and $1 million for the three and nine months ended September 30, 2017, respectively. Comparative electric revenues at Ameren Illinois for the three and nine months ended September 30, 2016, were increased $11 million and $24 million, respectively, for the difference between the estimate of its revenue requirement and the revenue requirement reflected in customer rates.
In June 2017, pursuant to the FEJA, Ameren Illinois filed with the ICC an energy efficiency plan for 2018 through 2021. In September 2017, the ICC issued an order approving Ameren Illinois' implementation of FEJA electric energy efficiency savings targets and investments. Ameren Illinois plans to invest up to $99 million in electric energy efficiency programs per year from 2018 through 2021 that will earn a return. The electric energy efficiency program investments and the return on those investments will be collected from customers through a rider and will not be included in the IEIMA formula ratemaking process.
ATXI’s Illinois Rivers Project
In August 2017, the Illinois Circuit Court for Edgar County dismissed several of ATXI’s condemnation cases related to one segment in the Illinois Rivers project, which has an estimated segment cost of approximately $85 million, of which $32 million was invested as of September 30, 2017. These cases had been filed in order to obtain necessary easements and rights of way to complete the segment. The court found that required notice was not given to the relevant landowners during the underlying ICC proceeding. ATXI intends to appeal this decision. ATXI plans to complete the project in 2019; however, delays associated with the condemnation proceedings or an appeal arising from the order dismissing the Edgar County cases could delay the completion date. The other eight segments of the Illinois Rivers project are not affected by these proceedings. 
Federal
FERC Complaint Cases
In November 2013, a customer group filed a complaint case with the FERC seeking a reduction in the allowed base return on common equity for FERC-regulated transmission rate base under the MISO tariff from 12.38% to 9.15%. In September 2016, the FERC issued a final order in the November 2013 complaint case, which lowered the allowed base return on common equity for the 15-month period of November 2013 to February 2015 to 10.32%, or a 10.82% total allowed return on common equity with the inclusion of a 50 basis point incentive adder for participation in an RTO. The order required customer refunds, with interest, to be issued for that 15-month period. In the first six months of 2017, Ameren and Ameren Illinois refunded $21 million and $17 million, respectively, related to the November 2013 complaint case. In addition, the 10.82% allowed return on common equity has been reflected in rates since September 2016. The 10.82% allowed return on common equity may be replaced prospectively after the FERC issues a final order in the February 2015 complaint case, discussed below.
Since 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. MISO transmission owners have since filed a motion to dismiss the February 2015 complaint. See below for additional information about the motion. The February 2015 complaint case seeks a further reduction in the allowed base return on common equity for FERC-regulated transmission rate base under the MISO tariff. In June 2016, an administrative law judge issued an initial decision in the February 2015 complaint case, which, if approved by the FERC, would lower the allowed base return on common equity for the 15-month period of February 2015 to May 2016 to 9.70%, or a 10.20% total allowed return on equity with the inclusion of a 50 basis point incentive adder for participation in an RTO, and require customer refunds, with interest, for that 15-month period. The timing of the issuance of the final order in the February 2015 complaint case is uncertain for two reasons. First, while the FERC reestablished a quorum of commissioners in August 2017 after six months without a quorum, the FERC is under no deadline to issue a final order. Second, in the second quarter of 2017, the United States Court of Appeals for the District of Columbia Circuit vacated and remanded to the FERC an order in a separate case in which the FERC established the allowed base return on common equity methodology used in the two MISO complaint cases described above. Ameren is unable to predict the impact of the outcome of the United States Court of Appeals for the District of Columbia Circuit’s remand on the MISO FERC complaint cases at this time. 
In September 2017, MISO transmission owners, including Ameren Missouri, Ameren Illinois, and ATXI, filed a motion to dismiss the February 2015 complaint case with the FERC. The MISO transmission owners maintain that the February 2015 complaint was predicated on the now superseded 12.38% allowed base return on common equity being an unjust and unreasonable return and is not applicable given the currently effective 10.32% allowed base return on common equity. The MISO transmission owners further maintain that the currently effective 10.32% allowed base return on common equity has not been proven to be unjust and unreasonable based on information provided, including the base return on common equity methodology ranges set forth in the February 2015 complaint case and the initial decision issued by an administrative law judge in June 2016. Additionally, the MISO transmission owners maintain that the February 2015 complaint should be dismissed because the approach utilized in the case to assert that a return on common equity was unjust and unreasonable is insufficient. That same approach was rejected by the United States Court of Appeals for the District of Columbia Circuit, as discussed above. FERC is under no deadline to issue an order on this motion.
As of September 30, 2017, Ameren and Ameren Illinois had recorded current regulatory liabilities of $41 million and $24 million, respectively, to reflect the expected refunds, including interest, associated with the reduced allowed returns on common equity in the initial decision in the February 2015 complaint case. Ameren Missouri does not expect that a reduction in the FERC-allowed base return on common equity would be material to its results of operations, financial position, or liquidity.
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. See Note 4 – Short-term Debt and Liquidity under Part II, Item 8, in the Form 10-K for a description of our indebtedness provisions and other covenants as well as a description of money pool arrangements.
The Missouri Credit Agreement and the Illinois Credit Agreement, both of which expire in December 2021, were not utilized for direct borrowings during the nine months ended September 30, 2017, but were used to support commercial paper issuances and to issue letters of credit. Based on commercial paper outstanding, as well as letters of credit issued under the Credit Agreements, the aggregate amount of credit capacity available under the Credit Agreements to Ameren (parent), Ameren Missouri, and Ameren Illinois, collectively, at September 30, 2017, was $1.7 billion. The Ameren Companies were in compliance with the covenants in their Credit Agreements as of September 30, 2017. As of September 30, 2017, the ratios of consolidated indebtedness to consolidated total capitalization, calculated in accordance with the provisions of the Credit Agreements, were 51%, 47%, and 46% for Ameren, Ameren Missouri, and Ameren Illinois, respectively.
Commercial Paper
The following table presents commercial paper outstanding as of September 30, 2017, and December 31, 2016:
  
2017
 
2016
Ameren (parent)
$
277

 
$
507

Ameren Missouri
—

 
—

Ameren Illinois
169

 
51

Ameren Consolidated
$
446

 
$
558

The following table summarizes the borrowing activity and relevant interest rates under Ameren’s (parent), Ameren Missouri’s, and Ameren Illinois’ commercial paper programs for the nine months ended September 30, 2017 and 2016:
 
 
Ameren
(parent)
Ameren
Missouri
Ameren
Illinois
Ameren Consolidated
2017
 
 
 
 
 
 
Average daily commercial paper outstanding
 
$
669

 
$
7

$
78

$
754

Weighted-average interest rate
 
1.27
%
 
1.20
%
1.28
%
1.27
%
Peak commercial paper during period(a)
 
$
841

 
$
64

$
193

$
948

Peak interest rate
 
1.50
%
 
1.41
%
1.50
%
1.50
%
2016
 
 
 
 
 
 
Average daily commercial paper outstanding
 
$
435

 
$
80

$
48

$
563

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

 
$
208

$
195

$
839

Peak interest rate
 
0.95
%
 
0.85
%
0.85
%
0.95
%

(a)
The timing of peak commercial paper issuances varies by company. Therefore, the sum of peak commercial paper issuances presented by company does not equal the Ameren Consolidated peak commercial paper issuances for the period.
Money Pools
Ameren has money pool agreements with and among its subsidiaries to coordinate and provide for short-term cash and working capital requirements. The average interest rate for borrowing under the utility money pool for the three and nine months ended September 30, 2017, was 1.24% and 1.18%, respectively (2016 – 0.53% and 0.54%, 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 nine months ended September 30, 2017 and 2016.
Long-Term Debt And Equity Financings
LONG-TERM DEBT AND EQUITY FINANCINGS
LONG-TERM DEBT AND EQUITY FINANCINGS
Ameren Missouri
In June 2017, Ameren Missouri issued $400 million principal amount of 2.95% senior secured notes, due June 2027, with interest payable semiannually on June 15 and December 15 of each year, beginning in December 2017. Ameren Missouri received proceeds of $396 million, which were used, in conjunction with other available funds, to repay at maturity in June 2017 $425 million principal amount of its 6.40% senior secured notes.
ATXI
In June 2017, pursuant to a note purchase agreement, ATXI agreed to issue $450 million principal amount of 3.43% senior unsecured notes, due 2050, through a private placement offering exempt from registration under the Securities Act of 1933, as amended. ATXI issued $150 million principal amount of the notes in June 2017 and the remaining $300 million principal amount of the notes in August 2017. ATXI received proceeds of $449 million from the notes, which were used by ATXI to repay existing short-term and long-term affiliate debt owed to Ameren (parent).
ATXI may prepay at any time not less than 5% of the principal amount of notes then outstanding at 100% of the principal amount plus a make-whole premium. In the event of a change of control, as defined in the agreement, each holder of notes may require ATXI to prepay the entire unpaid principal amount of the notes held by such holder at a price equal to 100% of the principal amount of such notes together with accrued and unpaid interest thereon. The following table presents the principal maturities schedule for the notes:
Payment Date
 
Principal Payment

August 2022
$
49.5

August 2024
 
49.5

August 2027
 
49.5

August 2030
 
49.5

August 2032
 
49.5

August 2038
 
49.5

August 2043
 
76.5

August 2050
 
76.5

Total Principal Amount of Notes
$
450.0


The note purchase agreement includes financial covenants that require ATXI to not permit at any time: (i) debt to exceed 70% of total capitalization or (ii) secured debt to exceed 10% of total assets. The note purchase agreement also contains restrictive covenants that, among other things, restrict the ability of ATXI to: (i) enter into transactions with affiliates; (ii) consolidate, merge, transfer or lease all or substantially all of its assets; and (iii) create liens.
Indenture Provisions and Other Covenants
Ameren Missouri’s and Ameren Illinois’ indentures and articles of incorporation include covenants and provisions related to issuances of first mortgage bonds and preferred stock. Ameren Missouri and Ameren Illinois are required to meet certain ratios to issue additional first mortgage bonds and preferred stock. A failure to achieve these ratios would not result in a default under these covenants and provisions, but would restrict the companies’ ability to issue first mortgage bonds or preferred stock. See Note 5 – Long-Term Debt and Equity Financings under Part II, Item 8, in the Form 10-K for a description of our indenture provisions and other covenants as well as restrictions on the payment of dividends. See the discussion above for covenants related to ATXI’s note purchase agreement. At September 30, 2017, the Ameren Companies were in compliance with the provisions and covenants contained in their indentures and articles of incorporation, as applicable, and ATXI was in compliance with the provisions and covenants contained in its note purchase agreement.
Off-Balance-Sheet Arrangements
At September 30, 2017, none of the Ameren Companies had off-balance-sheet financing arrangements, other than operating leases entered into in the ordinary course of business, letters of credit, and Ameren parent guarantee arrangements on behalf of its subsidiaries.
Other Income and Expenses
OTHER INCOME AND EXPENSES
OTHER INCOME AND EXPENSES
The following table presents the components of “Other Income and Expenses” in the Ameren Companies’ statements of income for the three and nine months ended September 30, 2017 and 2016:
 
Three Months
 
Nine Months
 
 
2017
 
2016
 
2017
 
2016
 
Ameren:(a)
 
 
 
 
 
 
 
 
Miscellaneous income:
 
 
 
 
 
 
 
 
Allowance for equity funds used during construction
$
6

 
$
7

 
$
16

 
$
20

 
Interest income on industrial development revenue bonds
7

 
7

 
20

 
20

 
Interest income
—

 
3

 
5

 
11

 
Other
—

 
1

 
1

 
3

 
Total miscellaneous income
$
13

 
$
18

 
$
42

 
$
54

 
Miscellaneous expense:
 
 
 
 
 
 
 
 
Donations
$
—

 
$
1

 
$
7

 
$
8

 
Other
2

 
7

 
9

 
13

 
Total miscellaneous expense
$
2

 
$
8

 
$
16

 
$
21

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

 
$
6

 
$
15

 
$
16

 
Interest income on industrial development revenue bonds
7

 
7

 
20

 
20

 
Interest income
—

 
1

 
—

 
1

 
Other
—

 
—

 
1

  
1

 
Total miscellaneous income
$
13

 
$
14

 
$
36

 
$
38

 
Miscellaneous expense:
 
 
 
 
 
 
 
 
Donations
$
—

 
$
—

 
$
2

 
$
2

 
Other
2

 
2

 
4

 
4

 
Total miscellaneous expense
$
2

 
$
2

 
$
6

 
$
6

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

 
$
1

 
$
1

 
$
4

 
Interest income
1

 
2

 
5

 
9

 
Other
—

 
1

 
1

 
2

 
Total miscellaneous income
$
1

 
$
4

 
$
7

 
$
15

 
Miscellaneous expense:
 
 
 
 
 
 
 
 
Donations
$
—

 
$
1

 
$
5

 
$
6

 
Other
—

 
2

 
3

 
5

 
Total miscellaneous expense
$
—

 
$
3

 
$
8

 
$
11

 
(a)
Includes amounts for Ameren registrant and nonregistrant subsidiaries and intercompany eliminations.
Derivative Financial Instruments
DERIVATIVE FINANCIAL INSTRUMENTS
NOTE 6 – DERIVATIVE FINANCIAL INSTRUMENTS
We use derivatives to manage the risk of changes in market prices for natural gas, power, and uranium, as well as the risk of changes in rail transportation surcharges through fuel oil hedges. Such price fluctuations may cause the following:
•
an unrealized appreciation or depreciation of our contracted commitments to purchase or sell when purchase or sale prices under the commitments are compared with current commodity prices;
•
market values of natural gas and uranium inventories that differ from the cost of those commodities in inventory; and
•
actual cash outlays for the purchase of these commodities that differ from anticipated cash outlays.
The derivatives that we use to hedge these risks are governed by our risk management policies for forward contracts, futures, options, and swaps. Our net positions are continually assessed within our structured hedging programs to determine whether new or offsetting transactions are required. The goal of the hedging program is generally to mitigate financial risks while ensuring that sufficient volumes are available to meet our requirements. Contracts we enter into as part of our risk management program may be settled financially, settled by physical delivery, or net settled with the counterparty.
The following table presents open gross commodity contract volumes by commodity type for derivative assets and liabilities as of September 30, 2017, and December 31, 2016. As of September 30, 2017, these contracts extended through October 2019, March 2023, May 2032, and March 2020 for fuel oils, natural gas, power, and uranium, respectively.
  
Quantity (in millions, except as indicated)
 
2017
2016
Commodity
Ameren Missouri
Ameren Illinois
Ameren
Ameren Missouri
Ameren Illinois
Ameren
Fuel oils (in gallons)(a)
30

(b)

30

30

(b)

30

Natural gas (in mmbtu)
24

145

169

25

129

154

Power (in megawatthours)
2

9

11

1

9

10

Uranium (pounds in thousands)
370

(b)

370

345

(b)

345

(a)
Consists of ultra-low-sulfur diesel products.
(b)
Not applicable.
All contracts considered to be derivative instruments are required to be recorded on the balance sheet at their fair values, unless the NPNS exception applies. See Note 7 – Fair Value Measurements for a discussion of our methods of assessing the fair value of derivative instruments. Many of our physical contracts, such as our purchased power contracts, qualify for the NPNS exception to derivative accounting rules. The revenue or expense on NPNS contracts is recognized at the contract price upon physical delivery.
If we determine that a contract meets the definition of a derivative and is not eligible for the NPNS exception, we review the contract to determine whether the resulting gains or losses qualify for regulatory deferral. Derivative contracts that qualify for regulatory deferral are recorded at fair value, with changes in fair value recorded as regulatory assets or liabilities in the period in which the change occurs. We believe derivative losses and gains deferred as regulatory assets and liabilities are probable of recovery, or refund, through future rates charged to customers. Regulatory assets and liabilities are amortized to operating income as related losses and gains are reflected in rates charged to customers. Therefore, gains and losses on these derivatives have no effect on operating income. As of September 30, 2017, and December 31, 2016, all contracts that met the definition of a derivative and were not eligible for the NPNS exception received regulatory deferral.

The following table presents the carrying value and balance sheet location of all derivative commodity contracts, none of which were designated as hedging instruments, as of September 30, 2017, and December 31, 2016:
 
Balance Sheet Location
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
 
2017
 
 
 
 
 
 
 
Fuel oils
Other current assets
 
$
2

 
$
—

 
$
2

 
 
Other assets
 
1

 
—

 
1

 
Natural gas
Other current assets
 
—

 
1

 
1

 
 
Other assets
 
—

 
1

 
1

 
Power
Other current assets
 
10

 
—

 
10

 
 
Other assets
 
1

 
—

 
1

 
 
Total assets (a)
 
$
14

 
$
2

 
$
16

 
Fuel oils
Other current liabilities
 
$
2

 
$
—

 
$
2

 
Natural gas
Other current liabilities
 
3

 
8

 
11

 
 
Other deferred credits and liabilities
 
4

 
6

 
10

 
Power
Other current liabilities
 
1

 
13

 
14

 
 
Other deferred credits and liabilities
 
—

 
179

 
179

 
Uranium
Other deferred credits and liabilities
 
—

(b) 
—

 
—

(b) 
 
Total liabilities (c)
 
$
10

 
$
206

 
$
216

 
2016
 
 
 
 
 
 
 
Fuel oils
Other current assets
 
$
2

 
$
—

 
$
2

 
 
Other assets
 
1

 
—

 
1

 
Natural gas
Other current assets
 
1

 
11

 
12

 
 
Other assets
 
1

 
2

 
3

 
Power
Other current assets
 
9

 
—

 
9

 
 
Total assets (a)
 
$
14

 
$
13

 
$
27

 
Fuel oils
Other current liabilities
 
$
5

 
$
—

 
$
5

 
Natural gas
Other current liabilities
 
1

 
3

 
4

 
 
Other deferred credits and liabilities
 
5

 
5

 
10

 
Power
Other current liabilities
 
3

 
12

 
15

 
 
Other deferred credits and liabilities
 
—

 
173

 
173

 
Uranium
Other deferred credits and liabilities
 
4

 
—

 
4

 
 
Total liabilities (c)
 
$
18

 
$
193

 
$
211

 

(a)
The cumulative amount of pretax net gains on all derivative instruments is deferred as a regulatory liability.
(b)
Beginning in 2017, as a result of rulebook amendments at the Chicago Mercantile Exchange, the fair value of uranium derivative liabilities are offset by certain settlement payments made to the exchange previously characterized as collateral and included within “Other assets” on Ameren’s and Ameren Missouri’s balance sheet.
(c)
The cumulative amount of pretax net losses on all derivative instruments is deferred as a regulatory asset.
Derivative instruments are subject to various credit-related losses in the event of nonperformance by counterparties to the transaction. Exchange-traded contracts are supported by the financial and credit quality of the clearing members of the respective exchanges; these contracts have nominal credit risk. In all other transactions, we are exposed to credit risk. Our credit risk management program involves establishing credit limits and collateral requirements for counterparties, using master netting arrangements or similar agreements, and reporting daily exposure to senior management.
We believe that entering into master netting arrangements or similar agreements mitigates the level of financial loss that could result from default by allowing net settlement of derivative assets and liabilities. These master netting arrangements allow the counterparties to net settle sale and purchase transactions. Further, collateral requirements are calculated at the master netting arrangement or similar agreement level by counterparty.
The Ameren Companies elect to present the fair value amounts of derivative assets and derivative liabilities subject to an enforceable master netting arrangement or similar agreement gross on the balance sheet. However, if the gross amounts recognized on the balance sheet were netted with derivative instruments and cash collateral received or posted, the net amounts would not be materially different from the gross amounts at September 30, 2017, and December 31, 2016.
Concentrations of Credit Risk
In determining our concentrations of credit risk related to derivative instruments, we review our individual counterparties and categorize each counterparty into groupings according to the primary business in which each engages. We calculate maximum exposures based on the gross fair value of financial instruments, including NPNS and other accrual contracts. These exposures are calculated on a gross basis, which include affiliate exposure not eliminated at the consolidated Ameren level. As of September 30, 2017, if counterparty groups were to fail completely to perform on contracts, the Ameren Companies’ maximum exposure would have been immaterial with or without consideration of the application of master netting arrangements or similar agreements and collateral held.
Derivative Instruments with Credit Risk-Related Contingent Features
Our commodity contracts contain collateral provisions tied to the Ameren Companies’ credit ratings. If our credit ratings were downgraded, or if a counterparty with reasonable grounds for uncertainty regarding our ability to satisfy an obligation requested adequate assurance of performance, additional collateral postings might be required. The following table presents, as of September 30, 2017, the aggregate fair value of all derivative instruments with credit risk-related contingent features in a gross liability position, the cash collateral posted, and the aggregate amount of additional collateral that counterparties could require. The additional collateral required is the net liability position allowed under the master netting arrangements or similar agreements, assuming (1) the credit risk-related contingent features underlying these arrangements were triggered on September 30, 2017, 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)
2017
 
 
 
 
 
Ameren Missouri
$
59

 
$
3

 
$
48

Ameren Illinois
48

 
—

 
41

Ameren
$
107

 
$
3

 
$
89

(a)
Before consideration of master netting arrangements or similar agreements and including NPNS and other accrual contract exposures.
(b)
As collateral requirements with certain counterparties are based on master netting arrangements or similar agreements, the aggregate amount of additional collateral required to be posted is determined after consideration of the effects of such arrangements.
Fair Value Measurements
FAIR VALUE MEASUREMENTS
FAIR VALUE MEASUREMENTS
Fair value is defined as the price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. We use various methods to determine fair value, including market, income, and cost approaches. With these approaches, we adopt certain assumptions that market participants would use in pricing the asset or liability, including assumptions about market risk or the risks inherent in the inputs to the valuation. Inputs to valuation can be readily observable, market-corroborated, or unobservable. We use valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs. Authoritative accounting guidance established a fair value hierarchy that prioritizes the inputs used to measure fair value.
All financial assets and liabilities carried at fair value are classified and disclosed in one of three hierarchy levels. See Note 8 – Fair Value Measurements under Part II, Item 8, of the Form 10-K for information related to hierarchy levels. We perform an analysis each quarter to determine the appropriate hierarchy level of the assets and liabilities subject to fair value measurements. Financial assets and liabilities are classified in their entirety according to the lowest level of input that is significant to the fair value measurement. All assets and liabilities whose fair value measurement is based on significant unobservable inputs are classified as Level 3.
The following table describes the valuation techniques and unobservable inputs utilized by the Ameren Companies for the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the periods ended September 30, 2017 and December 31, 2016:
 
 
Fair Value
 
 
 
Weighted Average
 
 
Assets
Liabilities

Valuation Technique(s)
Unobservable Input
Range
Level 3 Derivative asset and liability – commodity contracts(a):
 
 
 
2017
 
 
 
 
 
 
 
 
Fuel oils
$
1

$
(1
)
Option model
Volatilities(%)(b)
24 – 32
26
 
 
 
 
Discounted cash flow
Counterparty credit risk(%)(c)(d)
0.12 – 0.22
0.17
 
 
 
 
 
Ameren Missouri credit risk(%)(c)(d)
0.37
(e)
 
Natural gas
—

(2
)
Discounted cash flow
Nodal basis ($/mmbtu)(b)
(1.10) – (0.10)
(0.80)
 
 
 
 
 
Counterparty credit risk (%)(c)(d)
0.34 – 6
0.73
 
 
 
 
 
Ameren Illinois credit risk (%)(c)(d)
0.37
(e)
 
Power(g)
$
11

$
(193
)
Discounted cash flow
Average forward peak and off-peak pricing – forwards/swaps ($/MWh)(h)
25 – 41
28
 
 
 
 
 
Estimated auction price for FTRs ($/MW)(b)
(324) – 1,194
269
 
 
 
 
 
Nodal basis ($/MWh)(h)
(3) – 0
(2)
 
 
Fair Value
 
 
 
Weighted Average
 
 
Assets
Liabilities

Valuation Technique(s)
Unobservable Input
Range
 
 
 
 
 
Counterparty credit risk (%)(c)(d)
0.28
(e)
 
 
 
 
 
Ameren Illinois credit risk (%)(c)(d)
0.37
(e)
 
 
 
 
Fundamental energy production model
Estimated future natural gas prices ($/mmbtu)(b)
3 – 4
3
 
 
 
 
 
Escalation rate (%)(b)(i)
3
(e)
 
 
 
 
Contract price allocation
Estimated renewable energy credit costs ($/credit)(b)
5 – 7
6
2016
 
 
 
 
 
 
 
 
Fuel oils
$
1

$
—

Option model
Volatilities (%)(b)
24 – 66
28
 
 
 
 
Discounted cash flow
Counterparty credit risk (%)(c)(d)
0.13 – 0.22
0.15
 
 
 
 
 
Ameren Missouri credit risk (%)(c)(d)
0.38
(e)
 
 
 
 
 
Escalation rate (%)(b)(f)
(2) – 2
0
 
Natural gas
1

(1
)
Option model
Volatilities (%)(b)
31 – 66
36
 
 
 
 
 
Nodal basis ($/mmbtu)(b)
(0.40) – (0.10)
(0.20)
 
 
 
 
Discounted cash flow
Nodal basis ($/mmbtu)(b)
(0.80) – 0
(0.50)
 
 
 
 
 
Counterparty credit risk (%)(c)(d)
0.13 – 8
1
 
 
 
 
 
Ameren Illinois credit risk (%)(c)(d)
0.38
(e)
 
Power(g)
9

(187
)
Discounted cash flow
Average forward peak and off-peak pricing – forwards/swaps ($/MWh)(h)
26 – 44
29
 
 
 
 
 
Estimated auction price for FTRs ($/MW)(b)
(71) – 5,270
125
 
 
 
 
 
Nodal basis ($/MWh)(h)
(6) – 0
(2)
 
 
 
 
 
Ameren Illinois credit risk (%)(c)(d)
0.38
(e)
 
 
 
 
Fundamental energy production model
Estimated future natural gas prices ($/mmbtu)(b)
3 – 4
3
 
 
 
 
 
Escalation rate (%)(b)(i)
5
(e)
 
 
 
 
Contract price allocation
Estimated renewable energy credit costs ($/credit)(b)
5 – 7
6
 
Uranium
—

(4
)
Option model
Volatilities (%)(b)
24
(e)
 
 
 
 
Discounted cash flow
Average forward uranium pricing ($/pound)(b)
22 – 24
22
 
 
 
 
 
Ameren Missouri credit risk (%)(c)(d)
0.38
(e)

(a)
The derivative asset and liability balances are presented net of counterparty credit considerations.
(b)
Generally, significant increases (decreases) in this input in isolation would result in a significantly higher (lower) fair value measurement.
(c)
Generally, significant increases (decreases) in this input in isolation would result in a significantly lower (higher) fair value measurement.
(d)
Counterparty credit risk is applied only to counterparties with derivative asset balances. Ameren Missouri and Ameren Illinois credit risk is applied only to counterparties with derivative liability balances.
(e)
Not applicable.
(f)
Escalation rate applies to fuel oil prices 2019 and beyond.
(g)
Power valuations use visible third-party pricing evaluated by month for peak and off-peak demand through 2021 for September 30, 2017, and through 2020 for December 31, 2016. Valuations beyond 2021 for September 30, 2017, and 2020 for December 31, 2016 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.
(i)
Escalation rate applies to power prices in 2031 and beyond.
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 three and nine months ended September 30, 2017 or 2016. At September 30, 2017, and December 31, 2016, the counterparty default risk valuation adjustment related to derivative contracts was immaterial for Ameren, Ameren Missouri, and Ameren Illinois.
The following table sets forth, by level within the fair value hierarchy, our assets and liabilities measured at fair value on a recurring basis as of September 30, 2017:
 
 
 
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

 
$
—

 
$
1

 
$
3

 
 
Natural gas
 
1

 
1

 
—

 
2

 
 
Power
 
—

 
—

 
11

 
11

 
 
Total derivative assets – commodity contracts
 
$
3

 
$
1

 
$
12

 
$
16

 
 
Nuclear decommissioning trust fund:
 
 
 
 
 
 
 
 
 
 
Cash and cash equivalents
 
$
2

 
$
—

 
$
—

 
$
2

 
 
Equity securities:
 
 
 
 
 
 
 
 
 
 
U.S. large capitalization
 
445

 
—

 
—

 
445

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

 
119

 
—

 
119

 
 
Corporate bonds
 
—

 
82

 
—

 
82

 
 
Other
 
—

 
24

 
—

 
24

 
 
Total nuclear decommissioning trust fund
 
$
447

 
$
225

 
$
—

 
$
672

 
 
Total Ameren
 
$
450

 
$
226

 
$
12

 
$
688

 
Ameren Missouri
Derivative assets – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
2

 
$
—

 
$
1

 
$
3

 
 
Power
 
—

 
—

 
11

 
11

 
 
Total derivative assets – commodity contracts
 
$
2

 
$
—

 
$
12

 
$
14

 
 
Nuclear decommissioning trust fund:
 
 
 
 
 
 
 
 
 
 
Cash and cash equivalents
 
$
2

 
$
—

 
$
—

 
$
2

 
 
Equity securities:
 
 
 
 
 
 
 
 
 
 
U.S. large capitalization
 
445

 
—

 
—

 
445

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

 
119

 
—

 
119

 
 
Corporate bonds
 
—

 
82

 
—

 
82

 
 
Other
 
—

 
24

 
—

 
24

 
 
Total nuclear decommissioning trust fund
 
$
447

 
$
225

 
$
—

 
$
672

 
 
Total Ameren Missouri
 
$
449

 
$
225

 
$
12

 
$
686

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

 
$
1

 
$
—

 
$
2

 
Liabilities:
 
 
 
 
 
 
 
 
 
 
Ameren
Derivative liabilities – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
1

 
$
—

 
$
1

 
$
2

 
 
Natural gas
 
—

 
19

 
2

 
21

 
 
Power
 
—

 
—

 
193

 
193

 
 
Total Ameren
 
$
1

 
$
19

 
$
196

 
$
216

 
Ameren Missouri
Derivative liabilities – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
1

 
$
—

 
$
1

 
$
2

 
 
Natural gas
 
—

 
7

 
—

 
7

 
 
Power
 
—

 
—

 
1

 
1

 
 
Total Ameren Missouri
 
$
1

 
$
7

 
$
2

 
$
10

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

 
$
12

 
$
2

 
$
14

 
 
Power
 
—

 
—

 
192

 
192

 
 
Total Ameren Illinois
 
$
—

 
$
12

 
$
194

 
$
206

 
(a)
The derivative asset and liability balances are presented net of counterparty credit considerations.

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, 2016:
 
 
 
Quoted Prices in
Active Markets for
Identical Assets
or Liabilities
(Level 1)
 
Significant Other
Observable 
Inputs
(Level 2)
 
Significant Other
Unobservable
Inputs
(Level 3)
 
Total
 
Assets:
 
 
 
 
 
 
 
 
 
 
Ameren
Derivative assets – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
2

 
$
—

 
$
1

 
$
3

 
 
Natural gas
 
2

 
12

 
1

 
15

 
 
Power
 
—

 
—

 
9

 
9

 
 
Total derivative assets – commodity contracts
 
$
4

 
$
12

 
$
11

 
$
27

 
 
Nuclear decommissioning trust fund:
 
 
 
 
 
 
 
 
 
 
Cash and cash equivalents
 
$
1

 
$
—

 
$
—

 
$
1

 
 
Equity securities:
 
 
 
 
 
 
 
 
 
 
U.S. large capitalization
 
408

 
—

 
—

 
408

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

 
112

 
—

 
112

 
 
Corporate bonds
 
—

 
67

 
—

 
67

 
 
Other
 
—

 
17

 
—

 
17

 
 
Total nuclear decommissioning trust fund
 
$
409

 
$
196

 
$
—

 
$
605

(b) 
 
Total Ameren
 
$
413

 
$
208

 
$
11

 
$
632

 
Ameren Missouri
Derivative assets – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
2

 
$
—

 
$
1

 
$
3

 
 
Natural gas
 
—

 
1

 
1

 
2

 
 
Power
 
—

 
—

 
9

 
9

 
 
Total derivative assets – commodity contracts
 
$
2

 
$
1

 
$
11

 
$
14

 
 
Nuclear decommissioning trust fund:
 
 
 
 
 
 
 
 
 
 
Cash and cash equivalents
 
$
1

 
$
—

 
$
—

 
$
1

 
 
Equity securities:
 
 
 
 
 
 
 
 
 
 
U.S. large capitalization
 
408

 
—

 
—

 
408

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

 
112

 
—

 
112

 
 
Corporate bonds
 
—

 
67

 
—

 
67

 
 
Other
 
—

 
17

 
—

 
17

 
 
Total nuclear decommissioning trust fund
 
$
409

 
$
196

 
$
—

 
$
605

(b) 
 
Total Ameren Missouri
 
$
411

 
$
197

 
$
11

 
$
619

 
Ameren Illinois
Derivative assets – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Natural gas
 
$
2

 
$
11

 
$
—

 
$
13

 
Liabilities:
 
 
 
 
 
 
 
 
 
 
Ameren
Derivative liabilities – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
5

 
$
—

 
$
—

 
$
5

 
 
Natural gas
 
—

 
13

 
1

 
14

 
 
Power
 
—

 
1

 
187

 
188

 
 
Uranium
 
—

 
—

 
4

 
4

 
 
Total Ameren
 
$
5

 
$
14

 
$
192

 
$
211

 
Ameren Missouri
Derivative liabilities – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
5

 
$
—

 
$
—

 
$
5

 
 
Natural gas
 
—

 
6

 
—

 
6

 
 
Power
 
—

 
1

 
2

 
3

 
 
Uranium
 
—

 
—

 
4

 
4

 
 
Total Ameren Missouri
 
$
5

 
$
7

 
$
6

 
$
18

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

 
$
7

 
$
1

 
$
8

 
 
Power
 
—

 
—

 
185

 
185

 
 
Total Ameren Illinois
 
$
—

 
$
7

 
$
186

 
$
193

 
(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.
All costs related to financial assets and liabilities classified as Level 3 in the fair value hierarchy are expected to be recoverable through customer rates; therefore, there is no impact to net income resulting from changes in the fair value of these instruments. For the three and nine months ended September 30, 2017 and 2016, the balances and changes in the fair value of Level 3 financial assets and liabilities associated with fuel oils, natural gas, and uranium were immaterial.
The following table summarizes the changes in the fair value of power financial assets and liabilities classified as Level 3 in the fair value hierarchy:
  
 
Net derivative commodity contracts
 
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
For the three months ended September 30, 2017
 
 
 
 
 
 
Beginning balance at July 1, 2017
$
14

$
(192
)
$
(178
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities
 
(2
)
 
(3
)
 
(5
)
Sales
 
1

 
—

 
1

Settlements
 
(3
)
 
3

 
—

Ending balance at September 30, 2017
$
10

$
(192
)
$
(182
)
Change in unrealized gains (losses) related to assets/liabilities held at September 30, 2017
$
—

$
(2
)
$
(2
)
For the three months ended September 30, 2016
 
 
 
 
 
 
Beginning balance at July 1, 2016
$
14

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

 
(6
)
 
(6
)
Settlements
 
(5
)
 
3

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

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

$
(2
)
$
(2
)
For the nine months ended September 30, 2017
 
 
 
 
 
 
Beginning balance at January 1, 2017
$
7

$
(185
)
$
(178
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities
 
(3
)
 
(14
)
 
(17
)
Purchases
 
15

 
—

 
15

Sales
 
1

 
—

 
1

Settlements
 
(10
)
 
7

 
(3
)
Ending balance at September 30, 2017
$
10

$
(192
)
$
(182
)
Change in unrealized gains (losses) related to assets/liabilities held at September 30, 2017
$
—

$
(15
)
$
(15
)
For the nine months ended September 30, 2016
 
 
 
 
 
 
Beginning balance at January 1, 2016
$
16

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

 
—

 
13

Settlements
 
(16
)
 
11

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

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

$
(7
)
$
(7
)

Transfers into or out of Level 3 represent either (1) existing assets and liabilities that were previously categorized as a higher level, but were recategorized to Level 3 because the inputs to the model became unobservable during the period or (2) existing assets and liabilities that were previously classified as Level 3, but were recategorized to a higher level because the lowest significant input became observable during the period. For the three and nine months ended September 30, 2017 and 2016, there were no material transfers between Level 1 and Level 2, Level 1 and Level 3, or Level 2 and Level 3 related to derivative commodity contracts.
The Ameren Companies’ carrying amounts of cash and cash equivalents, accounts receivable, unbilled revenue, accounts payable, and other current financial instruments approximate fair value because of the short-term nature of these instruments. They are considered to be Level 1 in the fair value hierarchy. The Ameren Companies' short-term borrowings also approximate fair value because of their short-term nature. Short-term borrowings are considered to be Level 2 in the fair value hierarchy as they are valued based on market rates for similar market transactions. The estimated fair value of long-term debt and preferred stock is based on the quoted market prices for same or similar issuances for companies with similar credit profiles or on the current rates offered to the Ameren Companies for similar financial instruments, which fair value measurement is considered to be Level 2 in the fair value hierarchy.
The following table presents the carrying amounts and estimated fair values of our long-term debt, capital lease obligations and preferred stock at September 30, 2017, and December 31, 2016:
 
September 30, 2017
 
December 31, 2016
 
Carrying
Amount
 
Fair
Value
 
Carrying
Amount
 
Fair
Value
Ameren:
 
 
 
 
 
 
 
Long-term debt and capital lease obligations (including current portion)
$
7,699

 
$
8,234

 
$
7,276

 
$
7,772

Preferred stock(a)
142

 
131

 
142

 
131

Ameren Missouri:
 
 
 
 
 
 
 
Long-term debt and capital lease obligations (including current portion)
$
3,967

 
$
4,312

 
$
3,994

 
$
4,304

Preferred stock
80

 
79

 
80

 
79

Ameren Illinois:
 
 
 
 
 
 
 
Long-term debt (including current portion)
$
2,590

 
$
2,759

 
$
2,588

 
$
2,765

Preferred stock
62

 
52

 
62

 
52

(a)
Preferred stock is recorded in “Noncontrolling Interests” on the consolidated balance sheet.
Related Party Transactions
RELATED PARTY TRANSACTIONS
RELATED PARTY TRANSACTIONS
In the normal course of business, the Ameren Companies engage in affiliate transactions. 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 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 Agreement
In April 2017, Ameren Illinois conducted a procurement event, administered by the IPA, to purchase energy products. Ameren Missouri was among the winning suppliers in this event. As a result, in April 2017, Ameren Missouri and Ameren Illinois entered into an energy product agreement by which Ameren Missouri agreed to sell, and Ameren Illinois agreed to purchase, 85,600 megawatthours at an average price of $34 per megawatthour during the period of March 2019 through May 2020.
The following table presents the impact on Ameren Missouri and Ameren Illinois of related party transactions for the three and nine months ended September 30, 2017 and 2016:
 
 
 
 
Three Months
 
Nine Months
Agreement
Income Statement
Line Item
 
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
Missouri
 
Ameren
Illinois
Ameren Missouri power supply
Operating Revenues
2017
$
4

$
(a)

$
21

$
(a)

agreements with Ameren Illinois
 
2016
 
9

 
(a)

 
21

 
(a)

Ameren Missouri and Ameren Illinois
Operating Revenues
2017
 
7

 
1

 
20

 
3

rent and facility services
 
2016
 
5

 
1

 
18

 
3

Ameren Missouri and Ameren Illinois
Operating Revenues
2017
 
(b)

 
(b)

 
(b)

 
1

miscellaneous support services
 
2016
 
1

 
(b)

 
1

 
(b)

Total Operating Revenues
 
2017
$
11

$
1

$
41

$
4

 
 
2016
 
15

 
1

 
40

 
3

Ameren Illinois power supply
Purchased Power
2017
$
(a)

$
4

$
(a)

$
21

agreements with Ameren Missouri
 
2016
 
(a)

 
9

 
(a)

 
21

Ameren Illinois transmission
Purchased Power
2017
 
(a)

 
(b)

 
(a)

 
1

services with ATXI
 
2016
 
(a)

 
1

 
(a)

 
2

Total Purchased Power
 
2017
$
(a)

$
4

$
(a)

$
22

 
 
2016
 
(a)

 
10

 
(a)

 
23

Ameren Services support services
Other Operations and Maintenance
2017
$
34

$
33

$
103

$
99

agreement
 
2016
 
30

 
29

 
96

 
90

Money pool borrowings (advances)
Interest Charges/ Miscellaneous Income
2017
$
(b)

$
(b)

$
(b)

$
(b)

 
 
2016
 
(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 the 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, and Note 15 – Commitments and Contingencies 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, and Note 10 – Callaway Energy Center of this report.
Other Obligations
In April and September 2017, Ameren Illinois conducted procurement events, administered by the IPA, to purchase energy products through May 2020. In the April 2017 procurement event, Ameren Illinois contracted to purchase 4,249,800 megawatthours of energy products for $128 million from June 2017 through May 2020. In the September 2017 procurement event, Ameren Illinois contracted to purchase approximately 1,950,200 megawatthours of energy products for $57 million from October 2017 through May 2020. The results of both procurement events are reflected in the below table. See Note 8 – Related Party Transactions for additional information regarding energy product agreements between Ameren Missouri and Ameren Illinois as a result of the April procurement event.
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. Ameren Missouri and Ameren Illinois also have entered into various long-term commitments for purchased power and natural gas for distribution. The table below presents our estimated minimum fuel, purchased power, and other commitments for fuel at September 30, 2017. Ameren’s and Ameren Illinois’ purchased power commitments include the Ameren Illinois agreements entered into as part of the IPA-administered power procurement process. Included in the Other column are minimum purchase commitments under contracts for equipment, design and construction, and meter reading services, among other agreements, at September 30, 2017.
 
Coal
 
Natural
Gas(a)
 
Nuclear
Fuel
 
Purchased
Power(b)(c)
 
Methane
Gas
 
Other
 
Total
Ameren:(d)
 
 
 
 
 
 
 
 
 
 
 
 
 
2017
$
162

 
$
65

 
$
19

 
$
59

 
$
1

 
$
33

 
$
339

2018
453

 
200

 
67

 
170

 
4

 
57

 
951

2019
356

 
148

 
27

 
63

 
4

 
39

 
637

2020
79

 
94

 
39

 
13

 
5

 
39

 
269

2021
27

 
36

 
45

 
2

 
5

 
26

 
141

Thereafter
—

 
47

 
58

 
20

 
64

 
123

 
312

Total
$
1,077

 
$
590

 
$
255

 
$
327

 
$
83

 
$
317

 
$
2,649

Ameren Missouri:
 
 
 
 
 
 
 
 
 
 
 
 
 
2017
$
162

 
$
14

 
$
19

 
$
—

 
$
1

 
$
20

 
$
216

2018
453

 
42

 
67

 
—

 
4

 
44

 
610

2019
356

 
34

 
27

 
—

 
4

 
25

 
446

2020
79

 
26

 
39

 
—

 
5

 
25

 
174

2021
27

 
13

 
45

 
—

 
5

 
26

 
116

Thereafter
—

 
22

 
58

 
—

 
64

 
100

 
244

Total
$
1,077

 
$
151

 
$
255

 
$
—

 
$
83

 
$
240

 
$
1,806

Ameren Illinois:
 
 
 
 
 
 
 
 
 
 
 
 
 
2017
$
—

 
$
51

 
$
—

 
$
59

 
$
—

 
$
13

 
$
123

2018
—

 
158

 
—

 
170

 
—

 
13

 
341

2019
—

 
114

 
—

 
63

 
—

 
14

 
191

2020
—

 
68

 
—

 
13

 
—

 
14

 
95

2021
—

 
23

 
—

 
2

 
—

 
—

 
25

Thereafter
—

 
25

 
—

 
20

 
—

 
—

 
45

Total
$
—

 
$
439

 
$
—

 
$
327

 
$
—

 
$
54

 
$
820

(a)
Includes amounts for generation and for distribution.
(b)
The purchased power amounts for Ameren and Ameren Illinois exclude agreements for renewable energy credits through 2032 with various renewable energy suppliers due to the contingent nature of the payment amounts.
(c)
The purchased power amounts for Ameren and Ameren Missouri exclude a 102-megawatt power purchase agreement with a wind farm operator, which expires in 2024, due to the contingent nature of the payment amounts.
(d)
Includes amounts for Ameren registrant and nonregistrant subsidiaries.
Environmental Matters
We are subject to various environmental laws and regulations enforced by federal, state, and local authorities. The development and operation of electric generation, transmission, and distribution facilities and natural gas storage, transmission, and distribution facilities can trigger compliance obligations with respect to diverse environmental laws and regulations. These laws and regulations address emissions, discharges into water, water usage, impacts to air, land, and water, and chemical and waste handling. Complex and lengthy processes are required to obtain and renew approvals, permits, and licenses for new, existing or modified facilities. Additionally, the use and handling of various chemicals or hazardous materials require release prevention plans and emergency response procedures.
The EPA has promulgated environmental regulations that have a significant impact on the electric utility industry. Over time, compliance with these regulations could be costly for Ameren Missouri, which operates coal-fired power plants. As of December 31, 2016, Ameren Missouri’s fossil fuel-fired energy centers represented 18% and 34% of Ameren’s and Ameren Missouri’s rate base, respectively. Regulations impacting air emissions from the electric utility industry include the revised NSPS, the CSAPR, the MATS, and the revised National Ambient Air Quality Standards, which are subject to periodic review for certain pollutants. Collectively, these regulations cover a variety of pollutants such as SO2, particulate matter, NOX, mercury, toxic metals, and acid gases. Water intake and discharges from power plants are regulated under the Clean Water Act. Modifications to water intake structures and more stringent limitations or prohibitions against wastewater discharges at Ameren Missouri’s energy centers could result in significant capital expenditures. The management and disposal of coal ash is regulated under the CCR Rule, which will require the closure of surface impoundments and the installations of dry ash handling systems at several of Ameren Missouri’s energy centers, resulting in significant capital expenditures. The individual or combined effects of existing environmental regulations could result in significant capital expenditures, increased operating costs, the closure or alteration of the operation of some of Ameren Missouri’s energy centers, or require further capital investment. Ameren and Ameren Missouri expect that such compliance costs would be recoverable through rates, subject to MoPSC prudence review, but the timing of costs and their recovery could be subject to regulatory lag.
Ameren Missouri's current plan for compliance with existing air emission regulations includes burning ultra-low-sulfur coal and installing new or optimizing existing pollution control equipment. Ameren and Ameren Missouri estimate that they will need to make capital expenditures of $425 million to $525 million in the aggregate from 2017 through 2021 in order to comply with existing environmental regulations. Additional environmental controls beyond 2021 could be required. This estimate of capital expenditures includes expenditures required for the CCR regulations, Clean Water Act rules applicable to cooling water intake structures at existing power plants, and effluent limitation guidelines applicable to steam electric generating units, all of which are discussed below. The EPA has proposed to repeal the Clean Power Plan, which would have regulated CO2 emissions from power plants. The above capital expenditure amounts exclude estimated impacts from the Clean Power Plan. The actual amount of capital expenditures required to comply with existing environmental regulations may vary substantially from the above estimate because of uncertainty as to whether the EPA will substantively revise regulatory obligations, the precise compliance strategies that will be used and their ultimate cost, among other things.
The following sections describe the more significant environmental laws and rules and environmental enforcement and remediation matters that affect or could affect our operations. The EPA has initiated an administrative review of several regulations and rulemaking activities, including the effluent limitation guidelines and the CCR rule, which could ultimately result in the revision of all or part of such rules.
Clean Air Act
Federal and state laws require significant reductions in SO2 and NOx through either emission source reductions or the use and retirement of emission allowances. The first phase of the CSAPR emission reduction requirements became effective in 2015. The second phase of emission reduction requirements, which were revised by the EPA in 2016, became effective in 2017; additional emission reduction requirements may apply in subsequent years. To achieve compliance with the CSAPR, Ameren Missouri burns ultra-low-sulfur coal, operates two scrubbers at its Sioux energy center, and optimizes other existing pollution control equipment. Ameren Missouri did not make additional capital investments to comply with the 2017 CSAPR requirements. However, Ameren Missouri expects to incur additional costs to lower its emissions at one or more of its energy centers to comply with the CSAPR in future years. These higher costs are expected to be recovered from customers through the FAC or higher base rates.
CO2 Emissions Standards
In 2015, the EPA issued the Clean Power Plan, which sets forth CO2 emissions standards applicable to existing power plants. In October 2017, the EPA announced a proposal to repeal the Clean Power Plan and will seek public comment as to the scope of future regulations under the Clean Air Act. The United States Court of Appeals for the District of Columbia Circuit has stayed further action pending the EPA’s administrative review.
We cannot predict the outcome of the EPA’s future rulemaking, the outcome of legal challenges relating to either the repeal of the Clean Power Plan or such future rulemakings, nor the resulting impact on our results of operations, financial position, or liquidity.
NSR and Clean Air Litigation
In January 2011, the Department of Justice, on behalf of the EPA, filed a complaint against Ameren Missouri in the United States District Court for the Eastern District of Missouri. The complaint, as amended in October 2013, alleged 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. The litigation has been divided into two phases: liability and remedy. In January 2017, the district court issued a liability ruling that the projects violated provisions of the Clean Air Act and Missouri law. The case will now proceed to the second phase to determine the actions required to remedy the violations found in the liability phase of the litigation. The EPA previously withdrew all claims for penalties and fines. No date has been set by the district court for a trial on the remedy phase of the litigation. At the conclusion of both phases of the litigation, Ameren Missouri intends to appeal the liability ruling to the United States Court of Appeals for the Eighth Circuit.
The ultimate resolution of this matter could have a material adverse effect on the results of operations, financial position, and liquidity of Ameren and Ameren Missouri. Among other things, and subject to economic and regulatory considerations, resolution of this matter could result in increased capital expenditures for the installation of pollution control equipment, as well as increased operations and maintenance expenses. We are unable to predict the ultimate resolution of this matter or the costs that might be incurred.
Clean Water Act
In 2014, the EPA issued its final rule applicable to cooling water intake structures at existing power plants. The rule requires a case-by-case evaluation and plan for reducing aquatic organisms impinged on the facility’s intake screens or entrained through the plant's cooling water system. All of Ameren Missouri’s coal-fired and nuclear energy centers are subject to the cooling water intake structures rule. Implementation of the rule will occur during the permit renewal process of each energy center’s water discharge permit, which will occur between 2018 and 2023.
Additionally, in 2015, the EPA issued a rule to revise the effluent limitation guidelines applicable to steam electric generating units. These guidelines established national standards for water discharges that are based on the effectiveness of available control technology. The EPA's 2015 rule prohibits effluent discharges of certain waste streams and imposes more stringent limitations on certain water discharges from power plants. In September 2017, the EPA published a rule that postponed the compliance dates by two years for the limitations applicable to two specific waste streams so that it could potentially revise those standards.
Both the intake and effluent rules, if implemented as enacted, could have an adverse effect on Ameren’s and Ameren Missouri’s results of operations, financial position, and liquidity should such implementation require extensive modifications to the cooling water systems and water discharge systems at Ameren Missouri’s energy centers, and if such investments are not recovered on a timely basis in electric rates charged to Ameren Missouri’s customers.
Ash Management
In 2015, the EPA issued regulations regarding the management and disposal of CCR from coal-fired energy centers. These regulations affect CCR disposal and handling costs at Ameren Missouri's energy centers. They require closure of impoundments if performance criteria relating to groundwater impacts and location restrictions are not achieved. In September 2017, the EPA granted petitions filed on behalf of coal-fired electricity generators in which the EPA agreed to reconsider provisions of the CCR rules. Ameren and Ameren Missouri’s AROs associated with CCR storage facilities reflect the regulations issued in 2015. Ameren plans to close these CCR storage facilities between 2018 and 2024. Ameren Missouri's capital expenditure plan includes the cost of constructing landfills as part of its environmental compliance plan.
Remediation
The Ameren Companies are involved in a number of remediation actions to clean up sites impacted by the use or disposal of materials containing hazardous substances. Federal and state laws can require responsible parties to fund remediation regardless of their degree of fault, the legality of original disposal, or the ownership of a disposal site. Ameren Missouri and Ameren Illinois have each been identified by federal or state governments as a potentially responsible party at several contaminated sites.
As of September 30, 2017, Ameren Illinois owned or was otherwise responsible for 44 former MGP sites in Illinois, which are in various stages of investigation, evaluation, remediation, and closure. Ameren Illinois estimates it could substantially conclude remediation efforts by 2023. The ICC allows Ameren Illinois to recover remediation and litigation costs associated with its former MGP sites from its electric and natural gas utility customers through environmental adjustment rate riders. Costs are subject to annual review by the ICC. As of September 30, 2017, Ameren Illinois estimated the obligation related to these former MGP sites at $184 million to $255 million. Ameren and Ameren Illinois recorded a liability of $184 million to represent the estimated minimum obligation for these sites, as no other amount within the range was a better estimate.
The scope of the remediation activities at these former MGP sites may increase as remediation efforts continue. Considerable uncertainty remains in these estimates because many site-specific factors can influence the ultimate actual costs, including unanticipated underground structures, the degree to which groundwater is encountered, regulatory changes, local ordinances, and site accessibility. The actual costs and timing of completion may vary substantially from these estimates.
Ameren Missouri participated in the investigation of various sites known as Sauget Area 2, located in Sauget, Illinois. In 2000, the EPA notified Ameren Missouri and numerous other companies that former landfills and lagoons at those sites may contain soil and groundwater contamination. From about 1926 until 1976, Ameren Missouri operated an energy center adjacent to Sauget Area 2. Ameren Missouri currently owns a parcel of property at Sauget Area 2 that was once used by others as a landfill.
In 2013, the EPA issued its record of decision for Sauget Area 2, approving the investigation and the remediation actions recommended by the potentially responsible parties. Further negotiation among the potentially responsible parties will determine how to fund the implementation of the EPA-approved remedies. As of September 30, 2017, Ameren Missouri estimated its obligation related to Sauget Area 2 at $1 million to $2.5 million. Ameren Missouri recorded a liability of $1 million to represent its estimated minimum obligation for this site, as no other amount within the range was a better estimate.
Our operations or those of our predecessor companies involve the use of, disposal of, and, in appropriate circumstances, the cleanup of substances regulated under environmental laws. We are unable to determine whether such practices will result in future environmental commitments or will affect our results of operations, financial position, or liquidity.
Ameren Missouri Municipal Taxes
The cities of Creve Coeur and Winchester, Missouri, on behalf of themselves and other municipalities in Ameren Missouri’s service area, filed a class action lawsuit in 2011 against Ameren Missouri in the Circuit Court of St. Louis County, Missouri. The lawsuit alleges that Ameren Missouri failed to pay gross receipts taxes or license fees on certain revenues, including revenues from wholesale power and interchange sales. In the third quarter of 2017, the court issued an order preliminarily approving a settlement between Ameren Missouri and the plaintiffs, with final resolution of the case expected in the first quarter of 2018. Ameren and Ameren Missouri recorded immaterial liabilities on their respective balance sheets as of September 30, 2017, and December 31, 2016, representing their estimate of the probable loss due as a result of this lawsuit. Ameren and Ameren Missouri believe there is a remote possibility that a liability relating to this lawsuit could be material to Ameren's and Ameren Missouri’s results of operations, financial position, and liquidity.
Callaway Energy Center
CALLAWAY ENERGY CENTER
CALLAWAY ENERGY CENTER
Spent Nuclear Fuel
Under the NWPA, the DOE is responsible for disposing of spent nuclear fuel from the Callaway energy center and other commercial nuclear energy centers. The NWPA established the fee that Ameren Missouri and other utilities that own and operate those energy centers pay the federal government for disposing of the spent nuclear fuel at one mill, or one-tenth of one cent, for each kilowatthour generated and sold by those plants. The NWPA also requires the DOE to review the nuclear waste fee annually against the cost of the nuclear waste disposal program and to propose to the United States Congress any fee adjustment necessary to offset the costs of the program. As required by the NWPA, Ameren Missouri and other utilities have entered into standard contracts with the DOE. Consistent with the NWPA and its standard contract, which stated that the DOE would begin to dispose of spent nuclear fuel by 1998, Ameren Missouri had historically collected one mill from its electric customers for each kilowatthour of electricity that it generated and sold from its Callaway energy center. Because the federal government is not meeting its disposal obligation, the collection of this fee was suspended in May 2014. The DOE's delay in carrying out its obligation to dispose of spent nuclear fuel from the Callaway energy center is not expected to adversely affect the continued operations of the energy center.
As a result of the DOE's failure to fulfill its contractual obligations, Ameren Missouri and other nuclear energy center owners sued the DOE to recover costs incurred for ongoing storage of their spent fuel. The lawsuit resulted in a settlement agreement that provides for annual reimbursement of additional spent fuel storage and related costs. Ameren Missouri received reimbursements from the DOE of $3 million and $24 million in October 2017 and September 2016, respectively. Ameren Missouri will continue to apply for reimbursement from the DOE for allowable costs associated with the ongoing storage of spent fuel.
Decommissioning
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. An updated cost study and funding analysis was filed with the MoPSC in September 2017 and reflected within the ARO. Ameren Missouri’s filing supported no change in electric service rates for decommissioning costs. There is no deadline by which the MoPSC must issue an order regarding the filing.
The fair value of the trust fund for Ameren Missouri's Callaway energy center is reported as "Nuclear decommissioning trust fund" in Ameren's and Ameren Missouri's balance sheets. This amount is legally restricted and may be used only to fund the costs of nuclear decommissioning. Changes in the fair value of the trust fund are recorded as an increase or decrease to the nuclear decommissioning trust fund, with an offsetting adjustment to the related regulatory liability. If the assumed return on trust assets is not earned, Ameren Missouri believes that it is probable that any such earnings deficiency will be recovered in rates.
Supplier of Fuel Assemblies
Ameren Missouri received all necessary fuel assemblies for the fourth quarter 2017 refueling and maintenance outage. The Callaway energy center uses nuclear fuel assemblies fabricated by Westinghouse, which is the only NRC-licensed supplier authorized to provide fuel assemblies to the Callaway energy center. During the first quarter of 2017, Westinghouse filed voluntary petitions for a court-supervised restructuring process under Chapter 11 of the United States Bankruptcy Code. Westinghouse could petition the bankruptcy court to reject Ameren Missouri’s contracts as part of the restructuring process, and if the bankruptcy court agrees, this could result in Ameren Missouri not having access to the fuel assemblies necessary to refuel the Callaway energy center in future scheduled refueling and maintenance outages. At this time, Ameren and Ameren Missouri believe the restructuring proceeding will not affect Westinghouse’s performance under the terms of its existing contracts with Ameren Missouri, and therefore do not expect any material impact to Ameren Missouri’s operations as a result of this restructuring proceeding. However, Ameren and Ameren Missouri could incur material unexpected costs as a result of the Westinghouse bankruptcy, such as the loss of fuel inventory that is stored at Westinghouse’s facility and the cost of replacement power if nuclear fuel assemblies were not available for a future scheduled refueling and maintenance outage. A change of fuel suppliers or a change in the type of fuel assembly design that is currently licensed for use at the Callaway energy center could take an estimated three years of analysis and NRC licensing efforts to implement.
Insurance
The following table presents insurance coverage at Ameren Missouri’s Callaway energy center at September 30, 2017. The property coverage and the nuclear liability coverage renewal dates are April 1 and January 1, respectively, of each year. Both coverages were renewed in 2017.
Type and Source of Coverage
Maximum Coverages
 
Maximum Assessments
for Single Incidents
 
Public liability and nuclear worker liability:
 
 
 
 
American Nuclear Insurers
$
450

  
$
—

  
Pool participation
12,986

(a) 
127

(b) 
 
$
13,436

(c) 
$
127

  
Property damage:
 
 
 
 
NEIL and EMANI
$
3,200

(d) 
$
29

(e) 
Replacement power:
 
 
 
 
NEIL
$
490

(f) 
$
7

(e) 
(a)
Provided through mandatory participation in an industrywide retrospective premium assessment program.
(b)
Retrospective premium under the Price-Anderson Act. This is subject to retrospective assessment with respect to a covered loss in excess of $450 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. This limit is subject to change to account for the effects of inflation and changes in the number of licensed reactors.
(d)
NEIL provides $2.7 billion in property damage, stabilization, decontamination, and premature decommissioning insurance for radiation events and $2.3 billion in property damage insurance for nonradiation events. EMANI provides $490 million in property damage insurance for both radiation and nonradiation events.
(e)
All NEIL insured plants could be subject to assessments should losses exceed the accumulated funds from NEIL.
(f)
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 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 subject to industrywide aggregates, such that terrorist acts against one or more commercial nuclear power plants insured by NEIL or EMANI within a stated time period would be treated as a single event, and the owners of the nuclear power plants would share one full limit of liability. NEIL policies have an aggregate limit of $3.2 billion within a 12-month period for radiation events, or $1.8 billion for events not involving radiation contamination. The EMANI policies have an aggregate limit of €600 million for radiation and nonradiation events within a period of 72 hours.
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.
Retirement Benefits
RETIREMENT BENEFITS
RETIREMENT BENEFITS
The following table presents the components of the net periodic benefit cost (benefit), prior to capitalization, incurred for Ameren’s pension and postretirement benefit plans for the three and nine months ended September 30, 2017 and 2016:
  
Pension Benefits
 
Postretirement Benefits
 
 
Three Months
 
Nine Months
 
Three Months
 
Nine Months
 
  
2017
 
2016
 
2017
 
2016
 
2017
 
2016
 
2017
 
2016
 
Service cost
$
24

 
$
20

 
$
70

 
$
60

 
$
6

 
$
5

 
$
16

 
$
15

 
Interest cost
44

 
46

 
134

 
138

 
12

 
12

 
35

 
36

 
Expected return on plan assets
(65
)
 
(63
)
 
(196
)
 
(189
)
 
(19
)
 
(18
)
 
(56
)
 
(54
)
 
Amortization of:
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Prior service benefit
(1
)
 
—

 
(1
)
 
—

 
(2
)
 
(1
)
 
(4
)
 
(3
)
 
Actuarial loss (gain)
14

 
8

 
41

 
24

 
(2
)
 
(3
)
 
(5
)
 
(8
)
 
Net periodic benefit cost (benefit)
$
16

 
$
11

 
$
48

 
$
33

 
$
(5
)
 
$
(5
)
 
$
(14
)
 
$
(14
)
 

Ameren Missouri and Ameren Illinois are responsible for their respective shares of Ameren’s pension and postretirement costs. The following table presents the pension costs and the postretirement benefit costs (benefit) incurred for the three and nine months ended September 30, 2017 and 2016:
  
Pension Benefits
 
Postretirement Benefits
 
 
Three Months
 
Nine Months
 
Three Months
 
Nine Months
 
  
2017
 
2016
 
2017
 
2016
 
2017
 
2016
 
2017
 
2016
 
Ameren Missouri(a)
$
6

 
$
6

 
$
18

 
$
19

 
$
(1
)
 
$
(1
)
 
$
(3
)
 
$
(3
)
 
Ameren Illinois
10

 
6

 
30

 
17

 
(3
)
 
(3
)
 
(10
)
 
(10
)
 
Other
—

 
(1
)
 
—

 
(3
)
 
(1
)
 
(1
)
 
(1
)
 
(1
)
 
Ameren(a)(b)
$
16

 
$
11

 
$
48

 
$
33

 
$
(5
)
 
$
(5
)
 
$
(14
)
 
$
(14
)
 

(a)
Does not include the impact of the regulatory tracking mechanism for the difference between the level of pension and postretirement benefit costs incurred by Ameren Missouri under GAAP and the level of such costs included in rates.
(b)
Includes amounts for Ameren registrants and nonregistrant subsidiaries.
Segment Information
SEGMENT INFORMATION
SEGMENT INFORMATION
Ameren has four segments: Ameren Missouri, Ameren Illinois Electric Distribution, Ameren Illinois Natural Gas, and Ameren Transmission. The Ameren Missouri segment includes all of the operations of Ameren Missouri. Ameren Illinois Electric Distribution consists of the electric distribution business of Ameren Illinois. Ameren Illinois Natural Gas consists of the natural gas business of Ameren Illinois. Ameren Transmission is primarily composed of the aggregated electric transmission businesses of Ameren Illinois and ATXI. The category called Other primarily includes Ameren parent company activities and Ameren Services.
Ameren Missouri has one segment. Ameren Illinois has three segments: Ameren Illinois Electric Distribution, Ameren Illinois Natural Gas, and Ameren Illinois Transmission. See Note 1 – Summary of Significant Accounting Policies for additional information regarding the operations of Ameren Missouri, Ameren Illinois, and ATXI.
Segment operating revenues and a majority of operating expenses are directly recognized and incurred by Ameren Illinois to each Ameren Illinois segment. Common operating expenses, miscellaneous income and expenses, interest charges, and income tax expense are allocated by Ameren Illinois to each Ameren Illinois segment based on certain factors, which primarily relate to the nature of the cost. Additionally, Ameren Illinois Transmission earns revenue from transmission service provided to Ameren Illinois Electric Distribution. The transmission expense for Illinois customers who have elected to purchase their power from Ameren Illinois is recovered through a cost recovery mechanism with no net effect on Ameren Illinois Electric Distribution earnings, as costs are offset by corresponding revenues. Transmission revenues from these transactions are reflected at Ameren Transmission and Ameren Illinois Transmission. An intersegment elimination at Ameren and Ameren Illinois occurs to eliminate these transmission revenues and expenses.
The following tables present revenues, net income attributable to common shareholders, and capital expenditures by segment at Ameren and Ameren Illinois for the three and nine months ended September 30, 2017 and 2016. Ameren, Ameren Missouri, and Ameren Illinois management review segment capital expenditure information rather than any individual or total asset amount.
Ameren
Three Months
Ameren
Missouri
 
Ameren Illinois Electric Distribution
 
Ameren Illinois Natural Gas
 
Ameren Transmission
 
Other
 
Intersegment
Eliminations
 
Consolidated
 
2017
 
 
 
 
 
 
 
 
 
 
 
 
 
 
External revenues
$
1,104

 
$
405

 
$
111

 
$
105

 
$
(2
)
  
$
—

 
$
1,723

 
Intersegment revenues
11

 
—

 
1

 
14

(a) 
—

  
(26
)
 
—

 
Net income attributable to Ameren common shareholders
234

 
31

 
2

 
38

(b) 
(17
)
 
—

 
288

 
Capital expenditures
178

 
112

 
71

 
173

 
(2
)
 
(7
)
 
525

 
2016
 
 
 
 
 
 
 
 
 
 
 
 
 
 
External revenues
$
1,150

 
$
502

 
$
113

 
$
94

 
$
—

 
$
—

 
$
1,859

 
Intersegment revenues
15

 
1

 
1

 
14

(a) 
—

 
(31
)
 
—

 
Net income attributable to Ameren common shareholders
241

 
93

 
2

 
39

(b) 
(6
)
 
—

 
369

 
Capital expenditures
147

 
123

 
50

 
175

 
1

 
—

 
496

 
Nine Months
  
 
 
 
  
 
 
 
  
 
  
 
  
 
2017
 
 
 
 
 
 
 
 
 
 
 
 
 
 
External revenues
$
2,799

 
$
1,176

 
$
509

 
$
293

 
$
(2
)
 
$
—

 
$
4,775

 
Intersegment revenues
41

 
3

 
1

 
33

(a) 
—

 
(78
)
 
—

 
Net income attributable to Ameren common shareholders
359

 
94

 
40

 
106

(b) 
(16
)
 
—

 
583

 
Capital expenditures
533

 
354

 
180

 
463

 
3

 
(10
)
 
1,523

 
2016
 
 
 
 
 
 
 
 
 
 
 
 
 
 
External revenues
$
2,733

 
$
1,210

 
$
529

 
$
247

 
$
1

 
$
—

 
$
4,720

 
Intersegment revenues
40

 
3

 
1

 
36

(a) 
—

 
(80
)
 
—

 
Net income attributable to Ameren common shareholders
347

 
122

 
44

 
98

(b) 
10

 
—

 
621

 
Capital expenditures
500

 
359

 
130

 
503

 
4

 
—

 
1,496

 

(a)
Ameren Transmission earns revenue from transmission service provided to Ameren Illinois Electric Distribution. See discussion of transactions above.
(b)
Ameren Transmission earnings include an allocation of financing costs from Ameren (parent).

Ameren Illinois
Three Months
Ameren Illinois Electric Distribution
 
Ameren Illinois Natural Gas
 
Ameren Illinois Transmission
 
Intersegment
Eliminations
 
Consolidated
2017
 
 
 
 
 
 
 
 
 
External revenues
$
405

 
$
112

 
$
58

 
$
—

 
$
575

Intersegment revenues
—

 
—

 
14

(a) 
(14
)
 
—

Net income available to common shareholder
31

 
2

 
22

 
—

 
55

Capital expenditures
112

 
71

 
93

 
—

 
276

2016
 
 
 
 
 
 
 
 
 
External revenues
$
503

 
$
114

 
$
59

 
$
—

 
$
676

Intersegment revenues
—

 
—

 
14

(a) 
(14
)
 
—

Net income available to common shareholder
93

 
2

 
24

 
—

 
119

Capital expenditures
123

 
50

 
68

 
—

 
241

Nine Months
 
 
 
 
 
 
 
 
 
2017
 
 
 
 
 
 
 
 
 
External revenues
$
1,179

 
$
510

 
$
165

 
$
—

 
$
1,854

Intersegment revenues
—

 
—

 
32

(a) 
(32
)
 
—

Net income available to common shareholder
94

 
40

 
57

 
—

 
191

Capital expenditures
354

 
180

 
226

 
—

 
760

2016
 
 
 
 
 
 
 
 
 
External revenues
$
1,213

 
$
530

 
$
152

 
$
—

 
$
1,895

Intersegment revenues
—

 
—

 
35

(a) 
(35
)
 
—

Net income available to common shareholder
122

 
44

 
57

 
—

 
223

Capital expenditures
359

 
130

 
194

 
—

 
683


(a)
Ameren Illinois Transmission earns revenue from transmission service provided to Ameren Illinois Electric Distribution. See discussion of transactions above.
Summary Of Significant Accounting Policies (Policies)
9 Months Ended
Sep. 30, 2017
Accounting Policies [Abstract]
 
Consolidation
Text Block 
Revenue Recognition
The Ameren Companies record operating revenue for electric or natural gas service when it is delivered to customers. We accrue an estimate of electric and natural gas revenues for service rendered but unbilled at the end of each accounting period. For certain regulatory recovery mechanisms qualifying as alternative revenue programs, such as revenue requirement reconciliations, the Ameren Companies recognize revenues that have been authorized for rate recovery, are objectively determinable and probable of recovery, and are expected to be collected from customers within two years from the end of the year. 
Excise Taxes
Text Block 
Accounting and Reporting Developments
Text Block 
Consolidation 
Ameren’s financial statements are prepared on a consolidated basis and therefore include the accounts of its majority-owned subsidiaries. All intercompany transactions have been eliminated. Ameren Missouri and Ameren Illinois have no subsidiaries. All tabular dollar amounts are in millions, unless otherwise indicated. Also see the Glossary of Terms and Abbreviations at the front of this report and in the Form 10-K.
As of September 30, 2017 and December 31, 2016, Ameren had unconsolidated variable interests as a limited partner in various equity method investments, totaling $14 million and $9 million, respectively, included in “Other assets” on Ameren’s consolidated balance sheet. Ameren is not the primary beneficiary of these investments because it does not have the power to direct matters that most significantly impact the activities of these variable interest entities. As of September 30, 2017, the maximum exposure to loss related to these variable interests is limited to the investment in these partnerships of $14 million plus associated outstanding funding commitments of $23 million.
Our accounting policies conform to GAAP. Our financial statements reflect all adjustments (which include normal, recurring adjustments) that are necessary, in our opinion, for a fair statement of our results. The preparation of financial statements in conformity with GAAP requires management to make certain estimates and assumptions. Such estimates and assumptions affect reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the dates of financial statements, and the reported amounts of revenues and expenses during the reported periods. Actual results could differ from those estimates. The results of operations of an interim period may not give a true indication of results that may be expected for a full year. See Note 2 – Rate and Regulatory Matters for information regarding the 2017 change in Ameren Illinois' method used to recognize interim period revenue in connection with the revenue decoupling provisions of the FEJA. These financial statements should be read in conjunction with the financial statements and the notes thereto included in the Form 10-K.
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 – Natural 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 therefore are not included in Ameren Illinois’ revenues and expenses.
Accounting and Reporting Developments 
Below is a summary of updates related to our adoption of recently issued authoritative accounting standards. See Note 1 – Summary of Significant Accounting Policies under Part II, Item 8, of the Form 10-K for additional information about recently issued authoritative accounting standards relating to leases, financial instruments, and restricted cash.
Revenue from Contracts with Customers
In May 2014, the FASB issued authoritative guidance that changes the criteria for recognizing revenue from a contract with a customer. The underlying principle of the guidance is that an entity will recognize revenue for the transfer of promised goods or services to customers at an amount that the entity expects to be entitled to in exchange for those goods or services. The guidance 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, as well as separate presentation of alternative revenue programs on the income statement. Entities can apply the guidance to each reporting period presented (the full retrospective method) or by recording a cumulative effect adjustment to retained earnings in the period of initial adoption (the modified retrospective method).
We have substantially completed the evaluation of our contracts and do not expect material changes to the amount or timing of revenue recognition. We will finalize our contract assessments by the end of 2017. We will apply the guidance using the full retrospective method and include disaggregated revenue disclosures by segment and customer class in the combined notes to the financial statements in the first quarter of 2018.
Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost
In March 2017, the FASB issued authoritative guidance that requires an entity to retrospectively report the service cost component of net benefit cost in the same line item(s) as other compensation costs arising from services rendered by employees during the period and to present the other components of net benefit cost in the income statement separately from the service cost component and outside of operating income. The guidance also requires that an entity only capitalize the service cost component as part of an asset, such as inventory or property, plant, and equipment, on a prospective basis. Previously, all of the net benefit cost components were eligible for capitalization. This change in the capitalization of net benefit costs will not affect our ability to continue to obtain recovery of net benefit costs through customer rates. See Note 11 – Retirement Benefits for the components of net benefit cost. This guidance will be effective for the Ameren Companies in the first quarter of 2018. We are currently assessing the impacts of this guidance on our results of operations, financial position, and disclosures.
Derivative Financial Instruments Derivative Financial Instruments (Policies)
Derivatives
•
an unrealized appreciation or depreciation of our contracted commitments to purchase or sell when purchase or sale prices under the commitments are compared with current commodity prices;
•
market values of natural gas and uranium inventories that differ from the cost of those commodities in inventory; and
•
actual cash outlays for the purchase of these commodities that differ from anticipated cash outlays.
The derivatives that we use to hedge these risks are governed by our risk management policies for forward contracts, futures, options, and swaps. Our net positions are continually assessed within our structured hedging programs to determine whether new or offsetting transactions are required. The goal of the hedging program is generally to mitigate financial risks while ensuring that sufficient volumes are available to meet our requirements. Contracts we enter into as part of our risk management program may be settled financially, settled by physical delivery, or net settled with the counterparty.
Summary Of Significant Accounting Policies (Tables)
Asset Retirement Obligation Disclosure 
The following table provides a reconciliation of the beginning and ending carrying amount of AROs for the nine months ended September 30, 2017:
 
Ameren
Missouri
 
Ameren
Illinois(a)
 
Ameren
 
Balance at December 31, 2016
$
644

(b) 
$
6

 
$
650

(b) 
Liabilities settled
(4
)
 
(1
)
 
(5
)
 
Accretion(c)
20

 
(d)

 
20

 
Change in estimates(e)
(18
)
 
(1
)
 
(19
)
 
Balance at September 30, 2017
$
642

(b) 
$
4

 
$
646

(b) 
(a)
Included in “Other deferred credits and liabilities” on the balance sheet.
(b)
Balance included $15 million in “Other current liabilities” on the balance sheet as of both December 31, 2016 and September 30, 2017, respectively.
(c)
Accretion expense was recorded as a decrease to regulatory liabilities.
(d)
Less than $1 million.
(e)
Ameren Missouri changed its fair value estimate primarily due to an extension of the remediation period of certain CCR storage facilities, an update to the decommissioning of the Callaway energy center to reflect the cost study and funding analysis filed with the MoPSC in 2017, and an increase in the discount rate assumption.
Summary Of Nonvested Shares Related To Long-Term Incentive Plan 
A summary of nonvested performance share units at September 30, 2017, and changes during the nine months ended September 30, 2017, under the 2014 Incentive Plan are presented below:
 
Performance Share Units
 
Share Units
 
Weighted-average Fair Value per Share Unit
Nonvested at January 1, 2017
1,059,639

 
$
48.04

Granted(a)
500,943

 
59.16

Forfeitures
(48,661
)
 
52.54

Vested(b)
(27,446
)
 
52.88

Nonvested at September 30, 2017
1,484,475

 
$
51.55

(a)
Performance share units granted to certain executive and nonexecutive officers and other eligible employees under the 2014 Incentive Plan.
(b)
Performance share units vested due to the attainment of retirement eligibility by certain employees. Actual shares issued for retirement-eligible employees vary depending on actual performance over the three-year measurement period.
Schedule of Excise Taxes 
The following table presents excise taxes recorded in “Operating Revenues – Electric,” “Operating Revenues – Natural gas” and “Operating Expenses – Taxes other than income taxes” for the three and nine months ended September 30, 2017 and 2016:
 
Three Months
 
 
Nine Months
 
2017
 
2016
 
 
2017
 
2016
Ameren Missouri
$
51

 
$
52

 
 
$
122

 
$
122

Ameren Illinois
10

 
9

 
 
40

 
40

Ameren
$
61

 
$
61

 
 
$
162

 
$
162

Short-Term Debt And Liquidity Short-Term Debt and Liquidity (Tables)
Schedule of Short-term Debt
The following table presents commercial paper outstanding as of September 30, 2017, and December 31, 2016:
  
2017
 
2016
Ameren (parent)
$
277

 
$
507

Ameren Missouri
—

 
—

Ameren Illinois
169

 
51

Ameren Consolidated
$
446

 
$
558

The following table summarizes the borrowing activity and relevant interest rates under Ameren’s (parent), Ameren Missouri’s, and Ameren Illinois’ commercial paper programs for the nine months ended September 30, 2017 and 2016:
 
 
Ameren
(parent)
Ameren
Missouri
Ameren
Illinois
Ameren Consolidated
2017
 
 
 
 
 
 
Average daily commercial paper outstanding
 
$
669

 
$
7

$
78

$
754

Weighted-average interest rate
 
1.27
%
 
1.20
%
1.28
%
1.27
%
Peak commercial paper during period(a)
 
$
841

 
$
64

$
193

$
948

Peak interest rate
 
1.50
%
 
1.41
%
1.50
%
1.50
%
2016
 
 
 
 
 
 
Average daily commercial paper outstanding
 
$
435

 
$
80

$
48

$
563

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

 
$
208

$
195

$
839

Peak interest rate
 
0.95
%
 
0.85
%
0.85
%
0.95
%

(a)
The timing of peak commercial paper issuances varies by company. Therefore, the sum of peak commercial paper issuances presented by company does not equal the Ameren Consolidated peak commercial paper issuances for the period.
Long-Term Debt And Equity Financings Long Term Debt and Equity Financings (Tables)
Schedule of Maturities of Long-term Debt
The following table presents the principal maturities schedule for the notes:
Payment Date
 
Principal Payment

August 2022
$
49.5

August 2024
 
49.5

August 2027
 
49.5

August 2030
 
49.5

August 2032
 
49.5

August 2038
 
49.5

August 2043
 
76.5

August 2050
 
76.5

Total Principal Amount of Notes
$
450.0

Other Income and Expenses (Tables)
Other Income And Expenses
The following table presents the components of “Other Income and Expenses” in the Ameren Companies’ statements of income for the three and nine months ended September 30, 2017 and 2016:
 
Three Months
 
Nine Months
 
 
2017
 
2016
 
2017
 
2016
 
Ameren:(a)
 
 
 
 
 
 
 
 
Miscellaneous income:
 
 
 
 
 
 
 
 
Allowance for equity funds used during construction
$
6

 
$
7

 
$
16

 
$
20

 
Interest income on industrial development revenue bonds
7

 
7

 
20

 
20

 
Interest income
—

 
3

 
5

 
11

 
Other
—

 
1

 
1

 
3

 
Total miscellaneous income
$
13

 
$
18

 
$
42

 
$
54

 
Miscellaneous expense:
 
 
 
 
 
 
 
 
Donations
$
—

 
$
1

 
$
7

 
$
8

 
Other
2

 
7

 
9

 
13

 
Total miscellaneous expense
$
2

 
$
8

 
$
16

 
$
21

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

 
$
6

 
$
15

 
$
16

 
Interest income on industrial development revenue bonds
7

 
7

 
20

 
20

 
Interest income
—

 
1

 
—

 
1

 
Other
—

 
—

 
1

  
1

 
Total miscellaneous income
$
13

 
$
14

 
$
36

 
$
38

 
Miscellaneous expense:
 
 
 
 
 
 
 
 
Donations
$
—

 
$
—

 
$
2

 
$
2

 
Other
2

 
2

 
4

 
4

 
Total miscellaneous expense
$
2

 
$
2

 
$
6

 
$
6

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

 
$
1

 
$
1

 
$
4

 
Interest income
1

 
2

 
5

 
9

 
Other
—

 
1

 
1

 
2

 
Total miscellaneous income
$
1

 
$
4

 
$
7

 
$
15

 
Miscellaneous expense:
 
 
 
 
 
 
 
 
Donations
$
—

 
$
1

 
$
5

 
$
6

 
Other
—

 
2

 
3

 
5

 
Total miscellaneous expense
$
—

 
$
3

 
$
8

 
$
11

 
(a)
Includes amounts for Ameren registrant and nonregistrant subsidiaries and intercompany eliminations.
Derivative Financial Instruments (Tables)
Open Gross Derivative Volumes By Commodity Type 
The following table presents open gross commodity contract volumes by commodity type for derivative assets and liabilities as of September 30, 2017, and December 31, 2016. As of September 30, 2017, these contracts extended through October 2019, March 2023, May 2032, and March 2020 for fuel oils, natural gas, power, and uranium, respectively.
  
Quantity (in millions, except as indicated)
 
2017
2016
Commodity
Ameren Missouri
Ameren Illinois
Ameren
Ameren Missouri
Ameren Illinois
Ameren
Fuel oils (in gallons)(a)
30

(b)

30

30

(b)

30

Natural gas (in mmbtu)
24

145

169

25

129

154

Power (in megawatthours)
2

9

11

1

9

10

Uranium (pounds in thousands)
370

(b)

370

345

(b)

345

(a)
Consists of ultra-low-sulfur diesel products.
(b)
Not applicable.
Derivative Instruments Carrying Value 
The following table presents the carrying value and balance sheet location of all derivative commodity contracts, none of which were designated as hedging instruments, as of September 30, 2017, and December 31, 2016:
 
Balance Sheet Location
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
 
2017
 
 
 
 
 
 
 
Fuel oils
Other current assets
 
$
2

 
$
—

 
$
2

 
 
Other assets
 
1

 
—

 
1

 
Natural gas
Other current assets
 
—

 
1

 
1

 
 
Other assets
 
—

 
1

 
1

 
Power
Other current assets
 
10

 
—

 
10

 
 
Other assets
 
1

 
—

 
1

 
 
Total assets (a)
 
$
14

 
$
2

 
$
16

 
Fuel oils
Other current liabilities
 
$
2

 
$
—

 
$
2

 
Natural gas
Other current liabilities
 
3

 
8

 
11

 
 
Other deferred credits and liabilities
 
4

 
6

 
10

 
Power
Other current liabilities
 
1

 
13

 
14

 
 
Other deferred credits and liabilities
 
—

 
179

 
179

 
Uranium
Other deferred credits and liabilities
 
—

(b) 
—

 
—

(b) 
 
Total liabilities (c)
 
$
10

 
$
206

 
$
216

 
2016
 
 
 
 
 
 
 
Fuel oils
Other current assets
 
$
2

 
$
—

 
$
2

 
 
Other assets
 
1

 
—

 
1

 
Natural gas
Other current assets
 
1

 
11

 
12

 
 
Other assets
 
1

 
2

 
3

 
Power
Other current assets
 
9

 
—

 
9

 
 
Total assets (a)
 
$
14

 
$
13

 
$
27

 
Fuel oils
Other current liabilities
 
$
5

 
$
—

 
$
5

 
Natural gas
Other current liabilities
 
1

 
3

 
4

 
 
Other deferred credits and liabilities
 
5

 
5

 
10

 
Power
Other current liabilities
 
3

 
12

 
15

 
 
Other deferred credits and liabilities
 
—

 
173

 
173

 
Uranium
Other deferred credits and liabilities
 
4

 
—

 
4

 
 
Total liabilities (c)
 
$
18

 
$
193

 
$
211

 

(a)
The cumulative amount of pretax net gains on all derivative instruments is deferred as a regulatory liability.
(b)
Beginning in 2017, as a result of rulebook amendments at the Chicago Mercantile Exchange, the fair value of uranium derivative liabilities are offset by certain settlement payments made to the exchange previously characterized as collateral and included within “Other assets” on Ameren’s and Ameren Missouri’s balance sheet.
(c)
The cumulative amount of pretax net losses on all derivative instruments is deferred as a regulatory asset.
Derivative Instruments With Credit Risk-Related Contingent Features 
The following table presents, as of September 30, 2017, the aggregate fair value of all derivative instruments with credit risk-related contingent features in a gross liability position, the cash collateral posted, and the aggregate amount of additional collateral that counterparties could require. The additional collateral required is the net liability position allowed under the master netting arrangements or similar agreements, assuming (1) the credit risk-related contingent features underlying these arrangements were triggered on September 30, 2017, 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)
2017
 
 
 
 
 
Ameren Missouri
$
59

 
$
3

 
$
48

Ameren Illinois
48

 
—

 
41

Ameren
$
107

 
$
3

 
$
89

(a)
Before consideration of master netting arrangements or similar agreements and including NPNS and other accrual contract exposures.
(b)
As collateral requirements with certain counterparties are based on master netting arrangements or similar agreements, the aggregate amount of additional collateral required to be posted is determined after consideration of the effects of such arrangements.
Fair Value Measurements (Tables)
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis, Valuation Techniques 
The following table describes the valuation techniques and unobservable inputs utilized by the Ameren Companies for the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the periods ended September 30, 2017 and December 31, 2016:
 
 
Fair Value
 
 
 
Weighted Average
 
 
Assets
Liabilities

Valuation Technique(s)
Unobservable Input
Range
Level 3 Derivative asset and liability – commodity contracts(a):
 
 
 
2017
 
 
 
 
 
 
 
 
Fuel oils
$
1

$
(1
)
Option model
Volatilities(%)(b)
24 – 32
26
 
 
 
 
Discounted cash flow
Counterparty credit risk(%)(c)(d)
0.12 – 0.22
0.17
 
 
 
 
 
Ameren Missouri credit risk(%)(c)(d)
0.37
(e)
 
Natural gas
—

(2
)
Discounted cash flow
Nodal basis ($/mmbtu)(b)
(1.10) – (0.10)
(0.80)
 
 
 
 
 
Counterparty credit risk (%)(c)(d)
0.34 – 6
0.73
 
 
 
 
 
Ameren Illinois credit risk (%)(c)(d)
0.37
(e)
 
Power(g)
$
11

$
(193
)
Discounted cash flow
Average forward peak and off-peak pricing – forwards/swaps ($/MWh)(h)
25 – 41
28
 
 
 
 
 
Estimated auction price for FTRs ($/MW)(b)
(324) – 1,194
269
 
 
 
 
 
Nodal basis ($/MWh)(h)
(3) – 0
(2)
 
 
Fair Value
 
 
 
Weighted Average
 
 
Assets
Liabilities

Valuation Technique(s)
Unobservable Input
Range
 
 
 
 
 
Counterparty credit risk (%)(c)(d)
0.28
(e)
 
 
 
 
 
Ameren Illinois credit risk (%)(c)(d)
0.37
(e)
 
 
 
 
Fundamental energy production model
Estimated future natural gas prices ($/mmbtu)(b)
3 – 4
3
 
 
 
 
 
Escalation rate (%)(b)(i)
3
(e)
 
 
 
 
Contract price allocation
Estimated renewable energy credit costs ($/credit)(b)
5 – 7
6
2016
 
 
 
 
 
 
 
 
Fuel oils
$
1

$
—

Option model
Volatilities (%)(b)
24 – 66
28
 
 
 
 
Discounted cash flow
Counterparty credit risk (%)(c)(d)
0.13 – 0.22
0.15
 
 
 
 
 
Ameren Missouri credit risk (%)(c)(d)
0.38
(e)
 
 
 
 
 
Escalation rate (%)(b)(f)
(2) – 2
0
 
Natural gas
1

(1
)
Option model
Volatilities (%)(b)
31 – 66
36
 
 
 
 
 
Nodal basis ($/mmbtu)(b)
(0.40) – (0.10)
(0.20)
 
 
 
 
Discounted cash flow
Nodal basis ($/mmbtu)(b)
(0.80) – 0
(0.50)
 
 
 
 
 
Counterparty credit risk (%)(c)(d)
0.13 – 8
1
 
 
 
 
 
Ameren Illinois credit risk (%)(c)(d)
0.38
(e)
 
Power(g)
9

(187
)
Discounted cash flow
Average forward peak and off-peak pricing – forwards/swaps ($/MWh)(h)
26 – 44
29
 
 
 
 
 
Estimated auction price for FTRs ($/MW)(b)
(71) – 5,270
125
 
 
 
 
 
Nodal basis ($/MWh)(h)
(6) – 0
(2)
 
 
 
 
 
Ameren Illinois credit risk (%)(c)(d)
0.38
(e)
 
 
 
 
Fundamental energy production model
Estimated future natural gas prices ($/mmbtu)(b)
3 – 4
3
 
 
 
 
 
Escalation rate (%)(b)(i)
5
(e)
 
 
 
 
Contract price allocation
Estimated renewable energy credit costs ($/credit)(b)
5 – 7
6
 
Uranium
—

(4
)
Option model
Volatilities (%)(b)
24
(e)
 
 
 
 
Discounted cash flow
Average forward uranium pricing ($/pound)(b)
22 – 24
22
 
 
 
 
 
Ameren Missouri credit risk (%)(c)(d)
0.38
(e)

(a)
The derivative asset and liability balances are presented net of counterparty credit considerations.
(b)
Generally, significant increases (decreases) in this input in isolation would result in a significantly higher (lower) fair value measurement.
(c)
Generally, significant increases (decreases) in this input in isolation would result in a significantly lower (higher) fair value measurement.
(d)
Counterparty credit risk is applied only to counterparties with derivative asset balances. Ameren Missouri and Ameren Illinois credit risk is applied only to counterparties with derivative liability balances.
(e)
Not applicable.
(f)
Escalation rate applies to fuel oil prices 2019 and beyond.
(g)
Power valuations use visible third-party pricing evaluated by month for peak and off-peak demand through 2021 for September 30, 2017, and through 2020 for December 31, 2016. Valuations beyond 2021 for September 30, 2017, and 2020 for December 31, 2016 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.
(i)
Escalation rate applies to power prices in 2031 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 September 30, 2017:
 
 
 
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

 
$
—

 
$
1

 
$
3

 
 
Natural gas
 
1

 
1

 
—

 
2

 
 
Power
 
—

 
—

 
11

 
11

 
 
Total derivative assets – commodity contracts
 
$
3

 
$
1

 
$
12

 
$
16

 
 
Nuclear decommissioning trust fund:
 
 
 
 
 
 
 
 
 
 
Cash and cash equivalents
 
$
2

 
$
—

 
$
—

 
$
2

 
 
Equity securities:
 
 
 
 
 
 
 
 
 
 
U.S. large capitalization
 
445

 
—

 
—

 
445

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

 
119

 
—

 
119

 
 
Corporate bonds
 
—

 
82

 
—

 
82

 
 
Other
 
—

 
24

 
—

 
24

 
 
Total nuclear decommissioning trust fund
 
$
447

 
$
225

 
$
—

 
$
672

 
 
Total Ameren
 
$
450

 
$
226

 
$
12

 
$
688

 
Ameren Missouri
Derivative assets – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
2

 
$
—

 
$
1

 
$
3

 
 
Power
 
—

 
—

 
11

 
11

 
 
Total derivative assets – commodity contracts
 
$
2

 
$
—

 
$
12

 
$
14

 
 
Nuclear decommissioning trust fund:
 
 
 
 
 
 
 
 
 
 
Cash and cash equivalents
 
$
2

 
$
—

 
$
—

 
$
2

 
 
Equity securities:
 
 
 
 
 
 
 
 
 
 
U.S. large capitalization
 
445

 
—

 
—

 
445

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

 
119

 
—

 
119

 
 
Corporate bonds
 
—

 
82

 
—

 
82

 
 
Other
 
—

 
24

 
—

 
24

 
 
Total nuclear decommissioning trust fund
 
$
447

 
$
225

 
$
—

 
$
672

 
 
Total Ameren Missouri
 
$
449

 
$
225

 
$
12

 
$
686

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

 
$
1

 
$
—

 
$
2

 
Liabilities:
 
 
 
 
 
 
 
 
 
 
Ameren
Derivative liabilities – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
1

 
$
—

 
$
1

 
$
2

 
 
Natural gas
 
—

 
19

 
2

 
21

 
 
Power
 
—

 
—

 
193

 
193

 
 
Total Ameren
 
$
1

 
$
19

 
$
196

 
$
216

 
Ameren Missouri
Derivative liabilities – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
1

 
$
—

 
$
1

 
$
2

 
 
Natural gas
 
—

 
7

 
—

 
7

 
 
Power
 
—

 
—

 
1

 
1

 
 
Total Ameren Missouri
 
$
1

 
$
7

 
$
2

 
$
10

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

 
$
12

 
$
2

 
$
14

 
 
Power
 
—

 
—

 
192

 
192

 
 
Total Ameren Illinois
 
$
—

 
$
12

 
$
194

 
$
206

 
(a)
The derivative asset and liability balances are presented net of counterparty credit considerations.

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, 2016:
 
 
 
Quoted Prices in
Active Markets for
Identical Assets
or Liabilities
(Level 1)
 
Significant Other
Observable 
Inputs
(Level 2)
 
Significant Other
Unobservable
Inputs
(Level 3)
 
Total
 
Assets:
 
 
 
 
 
 
 
 
 
 
Ameren
Derivative assets – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
2

 
$
—

 
$
1

 
$
3

 
 
Natural gas
 
2

 
12

 
1

 
15

 
 
Power
 
—

 
—

 
9

 
9

 
 
Total derivative assets – commodity contracts
 
$
4

 
$
12

 
$
11

 
$
27

 
 
Nuclear decommissioning trust fund:
 
 
 
 
 
 
 
 
 
 
Cash and cash equivalents
 
$
1

 
$
—

 
$
—

 
$
1

 
 
Equity securities:
 
 
 
 
 
 
 
 
 
 
U.S. large capitalization
 
408

 
—

 
—

 
408

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

 
112

 
—

 
112

 
 
Corporate bonds
 
—

 
67

 
—

 
67

 
 
Other
 
—

 
17

 
—

 
17

 
 
Total nuclear decommissioning trust fund
 
$
409

 
$
196

 
$
—

 
$
605

(b) 
 
Total Ameren
 
$
413

 
$
208

 
$
11

 
$
632

 
Ameren Missouri
Derivative assets – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
2

 
$
—

 
$
1

 
$
3

 
 
Natural gas
 
—

 
1

 
1

 
2

 
 
Power
 
—

 
—

 
9

 
9

 
 
Total derivative assets – commodity contracts
 
$
2

 
$
1

 
$
11

 
$
14

 
 
Nuclear decommissioning trust fund:
 
 
 
 
 
 
 
 
 
 
Cash and cash equivalents
 
$
1

 
$
—

 
$
—

 
$
1

 
 
Equity securities:
 
 
 
 
 
 
 
 
 
 
U.S. large capitalization
 
408

 
—

 
—

 
408

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

 
112

 
—

 
112

 
 
Corporate bonds
 
—

 
67

 
—

 
67

 
 
Other
 
—

 
17

 
—

 
17

 
 
Total nuclear decommissioning trust fund
 
$
409

 
$
196

 
$
—

 
$
605

(b) 
 
Total Ameren Missouri
 
$
411

 
$
197

 
$
11

 
$
619

 
Ameren Illinois
Derivative assets – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Natural gas
 
$
2

 
$
11

 
$
—

 
$
13

 
Liabilities:
 
 
 
 
 
 
 
 
 
 
Ameren
Derivative liabilities – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
5

 
$
—

 
$
—

 
$
5

 
 
Natural gas
 
—

 
13

 
1

 
14

 
 
Power
 
—

 
1

 
187

 
188

 
 
Uranium
 
—

 
—

 
4

 
4

 
 
Total Ameren
 
$
5

 
$
14

 
$
192

 
$
211

 
Ameren Missouri
Derivative liabilities – commodity contracts(a):
 
 
 
 
 
 
 
 
 
 
Fuel oils
 
$
5

 
$
—

 
$
—

 
$
5

 
 
Natural gas
 
—

 
6

 
—

 
6

 
 
Power
 
—

 
1

 
2

 
3

 
 
Uranium
 
—

 
—

 
4

 
4

 
 
Total Ameren Missouri
 
$
5

 
$
7

 
$
6

 
$
18

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

 
$
7

 
$
1

 
$
8

 
 
Power
 
—

 
—

 
185

 
185

 
 
Total Ameren Illinois
 
$
—

 
$
7

 
$
186

 
$
193

 
(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 power financial assets and liabilities classified as Level 3 in the fair value hierarchy:
  
 
Net derivative commodity contracts
 
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
For the three months ended September 30, 2017
 
 
 
 
 
 
Beginning balance at July 1, 2017
$
14

$
(192
)
$
(178
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities
 
(2
)
 
(3
)
 
(5
)
Sales
 
1

 
—

 
1

Settlements
 
(3
)
 
3

 
—

Ending balance at September 30, 2017
$
10

$
(192
)
$
(182
)
Change in unrealized gains (losses) related to assets/liabilities held at September 30, 2017
$
—

$
(2
)
$
(2
)
For the three months ended September 30, 2016
 
 
 
 
 
 
Beginning balance at July 1, 2016
$
14

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

 
(6
)
 
(6
)
Settlements
 
(5
)
 
3

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

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

$
(2
)
$
(2
)
For the nine months ended September 30, 2017
 
 
 
 
 
 
Beginning balance at January 1, 2017
$
7

$
(185
)
$
(178
)
Realized and unrealized gains (losses) included in regulatory assets/liabilities
 
(3
)
 
(14
)
 
(17
)
Purchases
 
15

 
—

 
15

Sales
 
1

 
—

 
1

Settlements
 
(10
)
 
7

 
(3
)
Ending balance at September 30, 2017
$
10

$
(192
)
$
(182
)
Change in unrealized gains (losses) related to assets/liabilities held at September 30, 2017
$
—

$
(15
)
$
(15
)
For the nine months ended September 30, 2016
 
 
 
 
 
 
Beginning balance at January 1, 2016
$
16

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

 
—

 
13

Settlements
 
(16
)
 
11

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

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

$
(7
)
$
(7
)

Schedule Of Carrying Amounts And Estimated Fair Values Of Long-Term Debt, Capital Lease Obligations And Preferred Stock 
The following table presents the carrying amounts and estimated fair values of our long-term debt, capital lease obligations and preferred stock at September 30, 2017, and December 31, 2016:
 
September 30, 2017
 
December 31, 2016
 
Carrying
Amount
 
Fair
Value
 
Carrying
Amount
 
Fair
Value
Ameren:
 
 
 
 
 
 
 
Long-term debt and capital lease obligations (including current portion)
$
7,699

 
$
8,234

 
$
7,276

 
$
7,772

Preferred stock(a)
142

 
131

 
142

 
131

Ameren Missouri:
 
 
 
 
 
 
 
Long-term debt and capital lease obligations (including current portion)
$
3,967

 
$
4,312

 
$
3,994

 
$
4,304

Preferred stock
80

 
79

 
80

 
79

Ameren Illinois:
 
 
 
 
 
 
 
Long-term debt (including current portion)
$
2,590

 
$
2,759

 
$
2,588

 
$
2,765

Preferred stock
62

 
52

 
62

 
52

(a)
Preferred stock is recorded in “Noncontrolling Interests” on the consolidated balance sheet.
Related Party Transactions (Tables)
Schedule of Related Party Transactions
The following table presents the impact on Ameren Missouri and Ameren Illinois of related party transactions for the three and nine months ended September 30, 2017 and 2016:
 
 
 
 
Three Months
 
Nine Months
Agreement
Income Statement
Line Item
 
 
Ameren
Missouri
 
Ameren
Illinois
 
Ameren
Missouri
 
Ameren
Illinois
Ameren Missouri power supply
Operating Revenues
2017
$
4

$
(a)

$
21

$
(a)

agreements with Ameren Illinois
 
2016
 
9

 
(a)

 
21

 
(a)

Ameren Missouri and Ameren Illinois
Operating Revenues
2017
 
7

 
1

 
20

 
3

rent and facility services
 
2016
 
5

 
1

 
18

 
3

Ameren Missouri and Ameren Illinois
Operating Revenues
2017
 
(b)

 
(b)

 
(b)

 
1

miscellaneous support services
 
2016
 
1

 
(b)

 
1

 
(b)

Total Operating Revenues
 
2017
$
11

$
1

$
41

$
4

 
 
2016
 
15

 
1

 
40

 
3

Ameren Illinois power supply
Purchased Power
2017
$
(a)

$
4

$
(a)

$
21

agreements with Ameren Missouri
 
2016
 
(a)

 
9

 
(a)

 
21

Ameren Illinois transmission
Purchased Power
2017
 
(a)

 
(b)

 
(a)

 
1

services with ATXI
 
2016
 
(a)

 
1

 
(a)

 
2

Total Purchased Power
 
2017
$
(a)

$
4

$
(a)

$
22

 
 
2016
 
(a)

 
10

 
(a)

 
23

Ameren Services support services
Other Operations and Maintenance
2017
$
34

$
33

$
103

$
99

agreement
 
2016
 
30

 
29

 
96

 
90

Money pool borrowings (advances)
Interest Charges/ Miscellaneous Income
2017
$
(b)

$
(b)

$
(b)

$
(b)

 
 
2016
 
(b)

 
(b)

 
(b)

 
(b)

(a)
Not applicable.
(b)
Amount less than $1 million.
Commitments And Contingencies Commitments and Contingencies (Tables)
Long-term Purchase Commitment
The table below presents our estimated minimum fuel, purchased power, and other commitments for fuel at September 30, 2017. Ameren’s and Ameren Illinois’ purchased power commitments include the Ameren Illinois agreements entered into as part of the IPA-administered power procurement process. Included in the Other column are minimum purchase commitments under contracts for equipment, design and construction, and meter reading services, among other agreements, at September 30, 2017.
 
Coal
 
Natural
Gas(a)
 
Nuclear
Fuel
 
Purchased
Power(b)(c)
 
Methane
Gas
 
Other
 
Total
Ameren:(d)
 
 
 
 
 
 
 
 
 
 
 
 
 
2017
$
162

 
$
65

 
$
19

 
$
59

 
$
1

 
$
33

 
$
339

2018
453

 
200

 
67

 
170

 
4

 
57

 
951

2019
356

 
148

 
27

 
63

 
4

 
39

 
637

2020
79

 
94

 
39

 
13

 
5

 
39

 
269

2021
27

 
36

 
45

 
2

 
5

 
26

 
141

Thereafter
—

 
47

 
58

 
20

 
64

 
123

 
312

Total
$
1,077

 
$
590

 
$
255

 
$
327

 
$
83

 
$
317

 
$
2,649

Ameren Missouri:
 
 
 
 
 
 
 
 
 
 
 
 
 
2017
$
162

 
$
14

 
$
19

 
$
—

 
$
1

 
$
20

 
$
216

2018
453

 
42

 
67

 
—

 
4

 
44

 
610

2019
356

 
34

 
27

 
—

 
4

 
25

 
446

2020
79

 
26

 
39

 
—

 
5

 
25

 
174

2021
27

 
13

 
45

 
—

 
5

 
26

 
116

Thereafter
—

 
22

 
58

 
—

 
64

 
100

 
244

Total
$
1,077

 
$
151

 
$
255

 
$
—

 
$
83

 
$
240

 
$
1,806

Ameren Illinois:
 
 
 
 
 
 
 
 
 
 
 
 
 
2017
$
—

 
$
51

 
$
—

 
$
59

 
$
—

 
$
13

 
$
123

2018
—

 
158

 
—

 
170

 
—

 
13

 
341

2019
—

 
114

 
—

 
63

 
—

 
14

 
191

2020
—

 
68

 
—

 
13

 
—

 
14

 
95

2021
—

 
23

 
—

 
2

 
—

 
—

 
25

Thereafter
—

 
25

 
—

 
20

 
—

 
—

 
45

Total
$
—

 
$
439

 
$
—

 
$
327

 
$
—

 
$
54

 
$
820

(a)
Includes amounts for generation and for distribution.
(b)
The purchased power amounts for Ameren and Ameren Illinois exclude agreements for renewable energy credits through 2032 with various renewable energy suppliers due to the contingent nature of the payment amounts.
(c)
The purchased power amounts for Ameren and Ameren Missouri exclude a 102-megawatt power purchase agreement with a wind farm operator, which expires in 2024, due to the contingent nature of the payment amounts.
(d)
Includes amounts for Ameren registrant and nonregistrant subsidiaries.
Callaway Energy Center (Tables)
Schedule of Insurance Coverage at Callaway Energy Center
The following table presents insurance coverage at Ameren Missouri’s Callaway energy center at September 30, 2017. The property coverage and the nuclear liability coverage renewal dates are April 1 and January 1, respectively, of each year. Both coverages were renewed in 2017.
Type and Source of Coverage
Maximum Coverages
 
Maximum Assessments
for Single Incidents
 
Public liability and nuclear worker liability:
 
 
 
 
American Nuclear Insurers
$
450

  
$
—

  
Pool participation
12,986

(a) 
127

(b) 
 
$
13,436

(c) 
$
127

  
Property damage:
 
 
 
 
NEIL and EMANI
$
3,200

(d) 
$
29

(e) 
Replacement power:
 
 
 
 
NEIL
$
490

(f) 
$
7

(e) 
(a)
Provided through mandatory participation in an industrywide retrospective premium assessment program.
(b)
Retrospective premium under the Price-Anderson Act. This is subject to retrospective assessment with respect to a covered loss in excess of $450 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. This limit is subject to change to account for the effects of inflation and changes in the number of licensed reactors.
(d)
NEIL provides $2.7 billion in property damage, stabilization, decontamination, and premature decommissioning insurance for radiation events and $2.3 billion in property damage insurance for nonradiation events. EMANI provides $490 million in property damage insurance for both radiation and nonradiation events.
(e)
All NEIL insured plants could be subject to assessments should losses exceed the accumulated funds from NEIL.
(f)
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 limited to $328 million.
Retirement Benefits (Tables)
Components Of Net Periodic Benefit Cost 
The following table presents the components of the net periodic benefit cost (benefit), prior to capitalization, incurred for Ameren’s pension and postretirement benefit plans for the three and nine months ended September 30, 2017 and 2016:
  
Pension Benefits
 
Postretirement Benefits
 
 
Three Months
 
Nine Months
 
Three Months
 
Nine Months
 
  
2017
 
2016
 
2017
 
2016
 
2017
 
2016
 
2017
 
2016
 
Service cost
$
24

 
$
20

 
$
70

 
$
60

 
$
6

 
$
5

 
$
16

 
$
15

 
Interest cost
44

 
46

 
134

 
138

 
12

 
12

 
35

 
36

 
Expected return on plan assets
(65
)
 
(63
)
 
(196
)
 
(189
)
 
(19
)
 
(18
)
 
(56
)
 
(54
)
 
Amortization of:
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Prior service benefit
(1
)
 
—

 
(1
)
 
—

 
(2
)
 
(1
)
 
(4
)
 
(3
)
 
Actuarial loss (gain)
14

 
8

 
41

 
24

 
(2
)
 
(3
)
 
(5
)
 
(8
)
 
Net periodic benefit cost (benefit)
$
16

 
$
11

 
$
48

 
$
33

 
$
(5
)
 
$
(5
)
 
$
(14
)
 
$
(14
)
 

Summary Of Benefit Plan Costs Incurred 
Ameren Missouri and Ameren Illinois are responsible for their respective shares of Ameren’s pension and postretirement costs. The following table presents the pension costs and the postretirement benefit costs (benefit) incurred for the three and nine months ended September 30, 2017 and 2016:
  
Pension Benefits
 
Postretirement Benefits
 
 
Three Months
 
Nine Months
 
Three Months
 
Nine Months
 
  
2017
 
2016
 
2017
 
2016
 
2017
 
2016
 
2017
 
2016
 
Ameren Missouri(a)
$
6

 
$
6

 
$
18

 
$
19

 
$
(1
)
 
$
(1
)
 
$
(3
)
 
$
(3
)
 
Ameren Illinois
10

 
6

 
30

 
17

 
(3
)
 
(3
)
 
(10
)
 
(10
)
 
Other
—

 
(1
)
 
—

 
(3
)
 
(1
)
 
(1
)
 
(1
)
 
(1
)
 
Ameren(a)(b)
$
16

 
$
11

 
$
48

 
$
33

 
$
(5
)
 
$
(5
)
 
$
(14
)
 
$
(14
)
 

(a)
Does not include the impact of the regulatory tracking mechanism for the difference between the level of pension and postretirement benefit costs incurred by Ameren Missouri under GAAP and the level of such costs included in rates.
(b)
Includes amounts for Ameren registrants and nonregistrant subsidiaries.
Segment Information (Tables)
Schedule Of Segment Reporting Information By Segment
The following tables present revenues, net income attributable to common shareholders, and capital expenditures by segment at Ameren and Ameren Illinois for the three and nine months ended September 30, 2017 and 2016. Ameren, Ameren Missouri, and Ameren Illinois management review segment capital expenditure information rather than any individual or total asset amount.
Ameren
Three Months
Ameren
Missouri
 
Ameren Illinois Electric Distribution
 
Ameren Illinois Natural Gas
 
Ameren Transmission
 
Other
 
Intersegment
Eliminations
 
Consolidated
 
2017
 
 
 
 
 
 
 
 
 
 
 
 
 
 
External revenues
$
1,104

 
$
405

 
$
111

 
$
105

 
$
(2
)
  
$
—

 
$
1,723

 
Intersegment revenues
11

 
—

 
1

 
14

(a) 
—

  
(26
)
 
—

 
Net income attributable to Ameren common shareholders
234

 
31

 
2

 
38

(b) 
(17
)
 
—

 
288

 
Capital expenditures
178

 
112

 
71

 
173

 
(2
)
 
(7
)
 
525

 
2016
 
 
 
 
 
 
 
 
 
 
 
 
 
 
External revenues
$
1,150

 
$
502

 
$
113

 
$
94

 
$
—

 
$
—

 
$
1,859

 
Intersegment revenues
15

 
1

 
1

 
14

(a) 
—

 
(31
)
 
—

 
Net income attributable to Ameren common shareholders
241

 
93

 
2

 
39

(b) 
(6
)
 
—

 
369

 
Capital expenditures
147

 
123

 
50

 
175

 
1

 
—

 
496

 
Nine Months
  
 
 
 
  
 
 
 
  
 
  
 
  
 
2017
 
 
 
 
 
 
 
 
 
 
 
 
 
 
External revenues
$
2,799

 
$
1,176

 
$
509

 
$
293

 
$
(2
)
 
$
—

 
$
4,775

 
Intersegment revenues
41

 
3

 
1

 
33

(a) 
—

 
(78
)
 
—

 
Net income attributable to Ameren common shareholders
359

 
94

 
40

 
106

(b) 
(16
)
 
—

 
583

 
Capital expenditures
533

 
354

 
180

 
463

 
3

 
(10
)
 
1,523

 
2016
 
 
 
 
 
 
 
 
 
 
 
 
 
 
External revenues
$
2,733

 
$
1,210

 
$
529

 
$
247

 
$
1

 
$
—

 
$
4,720

 
Intersegment revenues
40

 
3

 
1

 
36

(a) 
—

 
(80
)
 
—

 
Net income attributable to Ameren common shareholders
347

 
122

 
44

 
98

(b) 
10

 
—

 
621

 
Capital expenditures
500

 
359

 
130

 
503

 
4

 
—

 
1,496

 

(a)
Ameren Transmission earns revenue from transmission service provided to Ameren Illinois Electric Distribution. See discussion of transactions above.
(b)
Ameren Transmission earnings include an allocation of financing costs from Ameren (parent).

Ameren Illinois
Three Months
Ameren Illinois Electric Distribution
 
Ameren Illinois Natural Gas
 
Ameren Illinois Transmission
 
Intersegment
Eliminations
 
Consolidated
2017
 
 
 
 
 
 
 
 
 
External revenues
$
405

 
$
112

 
$
58

 
$
—

 
$
575

Intersegment revenues
—

 
—

 
14

(a) 
(14
)
 
—

Net income available to common shareholder
31

 
2

 
22

 
—

 
55

Capital expenditures
112

 
71

 
93

 
—

 
276

2016
 
 
 
 
 
 
 
 
 
External revenues
$
503

 
$
114

 
$
59

 
$
—

 
$
676

Intersegment revenues
—

 
—

 
14

(a) 
(14
)
 
—

Net income available to common shareholder
93

 
2

 
24

 
—

 
119

Capital expenditures
123

 
50

 
68

 
—

 
241

Nine Months
 
 
 
 
 
 
 
 
 
2017
 
 
 
 
 
 
 
 
 
External revenues
$
1,179

 
$
510

 
$
165

 
$
—

 
$
1,854

Intersegment revenues
—

 
—

 
32

(a) 
(32
)
 
—

Net income available to common shareholder
94

 
40

 
57

 
—

 
191

Capital expenditures
354

 
180

 
226

 
—

 
760

2016
 
 
 
 
 
 
 
 
 
External revenues
$
1,213

 
$
530

 
$
152

 
$
—

 
$
1,895

Intersegment revenues
—

 
—

 
35

(a) 
(35
)
 
—

Net income available to common shareholder
122

 
44

 
57

 
—

 
223

Capital expenditures
359

 
130

 
194

 
—

 
683


(a)
Ameren Illinois Transmission earns revenue from transmission service provided to Ameren Illinois Electric Distribution. See discussion of transactions above.
Summary Of Significant Accounting Policies Summary of Significant Accounting Policies (Schedule of Asset Retirement Obligations) (Details) (USD $)
In Millions, unless otherwise specified
9 Months Ended
Sep. 30, 2017
Dec. 31, 2016
Asset Retirement Obligation [Line Items]
 
 
Balance
$ 646 1
$ 650 1
Liabilities settled
(5)
 
Accretion
20 2
 
Change of estimates
(19)3
 
Other current liabilities
318 
274 
Union Electric Company
 
 
Asset Retirement Obligation [Line Items]
 
 
Balance
642 1
644 1
Liabilities settled
(4)
 
Accretion
20 2
 
Change of estimates
(18)3
 
Other current liabilities
118 
123 
Ameren Illinois Company
 
 
Asset Retirement Obligation [Line Items]
 
 
Balance
4 4
6 4
Liabilities settled
(1)
 
Accretion
1 2 5
 
Change of estimates
(1)3 4
 
Other current liabilities
153 
109 
Asset Retirement Obligation Balance
 
 
Asset Retirement Obligation [Line Items]
 
 
Other current liabilities
15 
15 
Asset Retirement Obligation Balance |
Union Electric Company
 
 
Asset Retirement Obligation [Line Items]
 
 
Other current liabilities
$ 15 
$ 15 
Summary Of Significant Accounting Policies (Schedule Of Excise Taxes) (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Accounting Policies [Line Items]
 
 
 
 
Excise tax expense
$ 61 
$ 61 
$ 162 
$ 162 
Union Electric Company
 
 
 
 
Accounting Policies [Line Items]
 
 
 
 
Excise tax expense
51 
52 
122 
122 
Ameren Illinois Company
 
 
 
 
Accounting Policies [Line Items]
 
 
 
 
Excise tax expense
$ 10 
$ 9 
$ 40 
$ 40 
Summary Of Significant Accounting Policies Summary of Significant Accounting Policies (Narrative) (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2016
Basis Of Presentation And Significant Accounting Policies [Line Items]
 
 
 
 
 
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements
2.1 
0.3 
1.4 
0.4 
 
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net
$ 14 
 
$ 14 
 
$ 9 
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount
23 
 
23 
 
 
State and Local Jurisdiction [Member]
 
 
 
 
 
Basis Of Presentation And Significant Accounting Policies [Line Items]
 
 
 
 
 
State Income Tax Statutory Rate
 
 
7.75% 
 
 
Deferred Tax Liabilities, Net
97 
 
97 
 
 
Other Affiliated Entities and Intercompany Eliminations |
State and Local Jurisdiction [Member]
 
 
 
 
 
Basis Of Presentation And Significant Accounting Policies [Line Items]
 
 
 
 
 
Increase (Decrease) in Income Taxes
 
 
14 
 
 
Ameren Illinois Company |
State and Local Jurisdiction [Member]
 
 
 
 
 
Basis Of Presentation And Significant Accounting Policies [Line Items]
 
 
 
 
 
Increase (Decrease) in Income Taxes
 
 
1 
 
 
Deferred Tax Liabilities, Net
$ 79 
 
$ 79 
 
 
Maximum |
State and Local Jurisdiction [Member]
 
 
 
 
 
Basis Of Presentation And Significant Accounting Policies [Line Items]
 
 
 
 
 
State Income Tax Statutory Rate
 
 
9.50% 
 
 
Minimum |
State and Local Jurisdiction [Member]
 
 
 
 
 
Basis Of Presentation And Significant Accounting Policies [Line Items]
 
 
 
 
 
State Income Tax Statutory Rate
 
 
7.30% 
 
 
Rate And Regulatory Matters (Narrative-Missouri) (Detail) (Electric Distribution, Union Electric Company, USD $)
9 Months Ended
Sep. 30, 2017
Final Rate Order
 
Rate And Regulatory Matters [Line Items]
 
Revenue Requirement
$ 3,400,000,000 
Public Utilities, Requested Rate Increase (Decrease), Amount
92,000,000 
Components of Rate Increase - Net Energy Costs
 
Rate And Regulatory Matters [Line Items]
 
Public Utilities, Requested Rate Increase (Decrease), Amount
54,000,000 
Components of Rate Increase - Regulatory Amortizations
 
Rate And Regulatory Matters [Line Items]
 
Public Utilities, Requested Rate Increase (Decrease), Amount
$ 26,000,000 
Rate And Regulatory Matters (Narrative-Illinois) (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2016
Rate And Regulatory Matters [Line Items]
 
 
 
 
 
Regulatory assets
$ 1,509 
 
$ 1,509 
 
$ 1,437 
Current regulatory assets
75 
 
75 
 
149 
Regulatory liabilities
2,045 
 
2,045 
 
1,985 
Electric
1,594 
1,725 
4,183 
4,101 
 
Ameren Illinois Company
 
 
 
 
 
Rate And Regulatory Matters [Line Items]
 
 
 
 
 
Regulatory assets
921 
 
921 
 
816 
Current regulatory assets
51 
 
51 
 
108 
Regulatory liabilities
766 
 
766 
 
768 
Electric
463 
562 
1,343 
1,365 
 
Ameren Transmission Company of Illinois
 
 
 
 
 
Rate And Regulatory Matters [Line Items]
 
 
 
 
 
Estimated Capital Project Costs
 
 
85 
 
 
Property, Plant and Equipment, Additions
 
 
32 
 
 
IEIMA |
Ameren Illinois Company |
Electric Distribution
 
 
 
 
 
Rate And Regulatory Matters [Line Items]
 
 
 
 
 
Electric
76 
11 
1 
24 
 
2016 IEIMA Revenue Requirement Reconciliation |
IEIMA |
Ameren Illinois Company |
Electric Distribution
 
 
 
 
 
Rate And Regulatory Matters [Line Items]
 
 
 
 
 
Regulatory assets
24 
 
24 
 
 
2015 IEIMA Revenue Requirement Reconciliation |
IEIMA |
Ameren Illinois Company |
Electric Distribution
 
 
 
 
 
Rate And Regulatory Matters [Line Items]
 
 
 
 
 
Current regulatory assets
16 
 
16 
 
 
2017 IEIMA Revenue Requirement Reconciliation |
IEIMA |
Ameren Illinois Company |
Electric Distribution
 
 
 
 
 
Rate And Regulatory Matters [Line Items]
 
 
 
 
 
Regulatory liabilities
1 
 
1 
 
 
Pending Rate Case |
IEIMA |
Ameren Illinois Company |
Electric Distribution
 
 
 
 
 
Rate And Regulatory Matters [Line Items]
 
 
 
 
 
Public Utilities, Requested Rate Increase (Decrease), Amount
 
 
17 
 
 
FEJA |
Ameren Illinois Company |
Electric Distribution
 
 
 
 
 
Rate And Regulatory Matters [Line Items]
 
 
 
 
 
Public Utilities, Requested Equity Capital Structure, Percentage
 
 
50.00% 
 
 
FEJA 2018 through 2021 |
Ameren Illinois Company |
Electric Distribution
 
 
 
 
 
Rate And Regulatory Matters [Line Items]
 
 
 
 
 
FEJA Energy Efficiency Investments
 
 
$ 99 
 
 
Rate And Regulatory Matters (Narrative-Federal) (Detail) (USD $)
In Millions, unless otherwise specified
9 Months Ended 9 Months Ended
Sep. 30, 2017
Dec. 31, 2016
Sep. 30, 2017
Ameren Illinois Company
Dec. 31, 2016
Ameren Illinois Company
Sep. 30, 2017
Midwest Independent Transmission System Operator, Inc
Sep. 30, 2017
Midwest Independent Transmission System Operator, Inc
Final Rate Order
Sep. 30, 2017
Midwest Independent Transmission System Operator, Inc
Final Rate Order
Ameren Illinois Company
Sep. 30, 2017
Midwest Independent Transmission System Operator, Inc
Administrative Law Judge
Sep. 30, 2017
Midwest Independent Transmission System Operator, Inc
Pending Ferc Case
Sep. 30, 2017
Midwest Independent Transmission System Operator, Inc
Pending Ferc Case
Ameren Illinois Company
Sep. 30, 2017
Maximum
Midwest Independent Transmission System Operator, Inc
Final Rate Order
Sep. 30, 2017
Maximum
Midwest Independent Transmission System Operator, Inc
Administrative Law Judge
Rate And Regulatory Matters [Line Items]
 
 
 
 
 
 
 
 
 
 
 
 
Public Utilities, Approved Return on Equity, Percentage
 
 
 
 
12.38% 
10.32% 
 
9.70% 
 
 
10.82% 
10.20% 
Customer Requested Rate on Equity
 
 
 
 
 
9.15% 
 
 
 
 
 
 
Payments for Legal Settlements
 
 
 
 
 
$ 21 
$ 17 
 
 
 
 
 
Incentive adder to FERC allowed base return on common equity
 
 
 
 
 
0.50% 
 
 
 
 
 
 
Current regulatory liabilities
$ 119 
$ 110 
$ 85 
$ 78 
 
 
 
 
$ 41 
$ 24 
 
 
Short-Term Debt And Liquidity (Narrative) (Detail) (USD $)
In Billions, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Utilities
 
 
 
 
Line of Credit Facility [Line Items]
 
 
 
 
Short Term Debt, Weighted Average Interest Rate During Period
1.24% 
0.53% 
1.18% 
0.54% 
Credit Agreements
 
 
 
 
Line of Credit Facility [Line Items]
 
 
 
 
Line of credit facility, maximum borrowing capacity
$ 1.7 
 
$ 1.7 
 
Actual debt-to-capital ratio
0.51 
 
0.51 
 
Missouri Credit Agreement |
Union Electric Company
 
 
 
 
Line of Credit Facility [Line Items]
 
 
 
 
Actual debt-to-capital ratio
0.47 
 
0.47 
 
Illinois Credit Agreement |
Ameren Illinois Company
 
 
 
 
Line of Credit Facility [Line Items]
 
 
 
 
Actual debt-to-capital ratio
0.46 
 
0.46 
 
Short-Term Debt And Liquidity Short-Term Debt and Liquidity (Commercial Paper outstanding) (Details) (USD $)
In Millions, unless otherwise specified
Sep. 30, 2017
Dec. 31, 2016
Short-term Debt [Line Items]
 
 
Commercial paper outstanding
$ 446 
$ 558 
Ameren (parent)
 
 
Short-term Debt [Line Items]
 
 
Commercial paper outstanding
277 
507 
Union Electric Company
 
 
Short-term Debt [Line Items]
 
 
Commercial paper outstanding
0 
0 
Ameren Illinois Company
 
 
Short-term Debt [Line Items]
 
 
Commercial paper outstanding
$ 169 
$ 51 
Short-Term Debt And Liquidity Short-Term Debt and Liquidity (Commercial Paper) (Details) (USD $)
In Millions, unless otherwise specified
9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Short-term Debt [Line Items]
 
 
Average Daily Commercial Paper Borrowings Outstanding
$ 754 
$ 563 
Weighted-average interest rate
1.27% 
0.79% 
Peak commercial paper during period
948 1
839 1
Peak interest rate
1.50% 
0.95% 
Ameren (parent)
 
 
Short-term Debt [Line Items]
 
 
Average Daily Commercial Paper Borrowings Outstanding
669 
435 
Weighted-average interest rate
1.27% 
0.81% 
Peak commercial paper during period
841 1
574 1
Peak interest rate
1.50% 
0.95% 
Union Electric Company
 
 
Short-term Debt [Line Items]
 
 
Average Daily Commercial Paper Borrowings Outstanding
7 
80 
Weighted-average interest rate
1.20% 
0.74% 
Peak commercial paper during period
64 1
208 1
Peak interest rate
1.41% 
0.85% 
Ameren Illinois Company
 
 
Short-term Debt [Line Items]
 
 
Average Daily Commercial Paper Borrowings Outstanding
78 
48 
Weighted-average interest rate
1.28% 
0.72% 
Peak commercial paper during period
$ 193 1
$ 195 1
Peak interest rate
1.50% 
0.85% 
Long-Term debt and Equity Financings (Narrative) (Details) (USD $)
9 Months Ended
Sep. 30, 2017
Union Electric Company |
Senior Secured Notes, 2.95%, Due 2027 - $400 Issuance |
Secured Debt
 
Long-Term Debt And Equity Financings [Line Items]
 
Total principal amount of notes
$ 400,000,000 
State interest rate
2.95% 
Proceeds from Issuance of Secured Debt
396,000,000 
Union Electric Company |
Senior Secured Notes640 Due2017
 
Long-Term Debt And Equity Financings [Line Items]
 
State interest rate
6.40% 
Repayments of other long-term debt
425,000,000 
Ameren Transmission Company of Illinois
 
Long-Term Debt And Equity Financings [Line Items]
 
Redemption price, percentage
100.00% 
Ameren Transmission Company of Illinois |
Senior Unsecured Notes, 3.43%, Due 2050 |
Unsecured Debt
 
Long-Term Debt And Equity Financings [Line Items]
 
Total principal amount of notes
300,000,000 
State interest rate
3.43% 
Proceeds from issuance of unsecured debt
449,000,000 
Ratio of indebtedness to net capital
0.70 
Ratio of indebtedness to total assets
0.10 
Maximum |
Ameren Transmission Company of Illinois |
Senior Unsecured Notes, 3.43%, Due 2050 |
Unsecured Debt
 
Long-Term Debt And Equity Financings [Line Items]
 
Total principal amount of notes
450,000,000 
Minimum |
Ameren Transmission Company of Illinois
 
Long-Term Debt And Equity Financings [Line Items]
 
Redemption price, percentage
5.00% 
Minimum |
Ameren Transmission Company of Illinois |
Senior Unsecured Notes, 3.43%, Due 2050 |
Unsecured Debt
 
Long-Term Debt And Equity Financings [Line Items]
 
Total principal amount of notes
$ 150,000,000 
Long-Term Debt and Equity Financings (Schedule of Maturities of Long-Term Debt) (Details) (Ameren Transmission Company of Illinois, Unsecured Debt, USD $)
Sep. 30, 2017
August 2022
 
Debt Instrument [Line Items]
 
Repayments of principal in year five
$ 49,500,000 
August 2024
 
Debt Instrument [Line Items]
 
Repayments of principal after year five
49,500,000 
August 2027
 
Debt Instrument [Line Items]
 
Repayments of principal after year five
49,500,000 
August 2030
 
Debt Instrument [Line Items]
 
Repayments of principal after year five
49,500,000 
August 2032
 
Debt Instrument [Line Items]
 
Repayments of principal after year five
49,500,000 
August 2038
 
Debt Instrument [Line Items]
 
Repayments of principal after year five
49,500,000 
August 2043
 
Debt Instrument [Line Items]
 
Repayments of principal after year five
76,500,000 
August 2050
 
Debt Instrument [Line Items]
 
Repayments of principal after year five
76,500,000 
Senior Unsecured Notes, 3.43%, Due 2050
 
Debt Instrument [Line Items]
 
Total principal amount of notes
300,000,000 
Senior Unsecured Notes, 3.43%, Due 2050 |
Maximum
 
Debt Instrument [Line Items]
 
Total principal amount of notes
$ 450,000,000 
Other Income and Expenses (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Other Nonoperating Income (Expense) [Line Items]
 
 
 
 
Allowance for equity funds used during construction
$ 6 1
$ 7 1
$ 16 1
$ 20 1
Interest income on industrial development revenue bonds
7 1
7 1
20 1
20 1
Interest income
0 1
3 1
5 1
11 1
Other
0 1
1 1
1 1
3 1
Total miscellaneous income
13 1
18 1
42 1
54 1
Donations
0 1
1 1
7 1
8 1
Other
2 1
7 1
9 1
13 1
Total miscellaneous expense
2 1
8 1
16 1
21 1
Union Electric Company
 
 
 
 
Other Nonoperating Income (Expense) [Line Items]
 
 
 
 
Allowance for equity funds used during construction
6 
6 
15 
16 
Interest income on industrial development revenue bonds
7 
7 
20 
20 
Interest income
0 
1 
0 
1 
Other
0 
0 
1 
1 
Total miscellaneous income
13 
14 
36 
38 
Donations
0 
0 
2 
2 
Other
2 
2 
4 
4 
Total miscellaneous expense
2 
2 
6 
6 
Ameren Illinois Company
 
 
 
 
Other Nonoperating Income (Expense) [Line Items]
 
 
 
 
Allowance for equity funds used during construction
0 
1 
1 
4 
Interest income
1 
2 
5 
9 
Other
0 
1 
1 
2 
Total miscellaneous income
1 
4 
7 
15 
Donations
0 
1 
5 
6 
Other
0 
2 
3 
5 
Total miscellaneous expense
$ 0 
$ 3 
$ 8 
$ 11 
Derivative Financial Instruments (Open Gross Derivative Volumes By Commodity Type) (Detail)
Sep. 30, 2017
gal
Dec. 31, 2016
gal
Fuel Oils
 
 
Derivative [Line Items]
 
 
Quantity
30,000,000 1
30,000,000 1
Natural Gas
 
 
Derivative [Line Items]
 
 
Quantity
169,000,000 
154,000,000 
Power
 
 
Derivative [Line Items]
 
 
Quantity
11,000,000 
10,000,000 
Uranium
 
 
Derivative [Line Items]
 
 
Quantity
370,000 
345,000 
Union Electric Company |
Fuel Oils
 
 
Derivative [Line Items]
 
 
Quantity
30,000,000 1
30,000,000 1
Union Electric Company |
Natural Gas
 
 
Derivative [Line Items]
 
 
Quantity
24,000,000 
25,000,000 
Union Electric Company |
Power
 
 
Derivative [Line Items]
 
 
Quantity
2,000,000 
1,000,000 
Union Electric Company |
Uranium
 
 
Derivative [Line Items]
 
 
Quantity
370,000 
345,000 
Ameren Illinois Company |
Natural Gas
 
 
Derivative [Line Items]
 
 
Quantity
145,000,000 
129,000,000 
Ameren Illinois Company |
Power
 
 
Derivative [Line Items]
 
 
Quantity
9,000,000 
9,000,000 
Derivative Financial Instruments (Derivative Instruments Carrying Value) (Detail) (Not Designated As Hedging Instrument, USD $)
In Millions, unless otherwise specified
Sep. 30, 2017
Dec. 31, 2016
Derivative [Line Items]
 
 
Derivative assets
$ 16 1
$ 27 1
Derivative liabilities
216 2
211 2
Fuel Oils |
Other Current Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
2 
2 
Fuel Oils |
Other Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
1 
1 
Fuel Oils |
Other Current Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
2 
5 
Natural Gas |
Other Current Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
1 
12 
Natural Gas |
Other Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
1 
3 
Natural Gas |
Other Current Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
11 
4 
Natural Gas |
Other Deferred Credits And Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
10 
10 
Power |
Other Current Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
10 
9 
Power |
Other Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
1 
 
Power |
Other Current Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
14 
15 
Power |
Other Deferred Credits And Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
179 
173 
Uranium |
Other Deferred Credits And Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
0 3
4 
Union Electric Company
 
 
Derivative [Line Items]
 
 
Derivative assets
14 1
14 1
Derivative liabilities
10 2
18 2
Union Electric Company |
Fuel Oils |
Other Current Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
2 
2 
Union Electric Company |
Fuel Oils |
Other Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
1 
1 
Union Electric Company |
Fuel Oils |
Other Current Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
2 
5 
Union Electric Company |
Natural Gas |
Other Current Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
0 
1 
Union Electric Company |
Natural Gas |
Other Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
0 
1 
Union Electric Company |
Natural Gas |
Other Current Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
3 
1 
Union Electric Company |
Natural Gas |
Other Deferred Credits And Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
4 
5 
Union Electric Company |
Power |
Other Current Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
10 
9 
Union Electric Company |
Power |
Other Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
1 
 
Union Electric Company |
Power |
Other Current Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
1 
3 
Union Electric Company |
Power |
Other Deferred Credits And Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
0 
0 
Union Electric Company |
Uranium |
Other Deferred Credits And Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
0 3
4 
Ameren Illinois Company
 
 
Derivative [Line Items]
 
 
Derivative assets
2 1
13 1
Derivative liabilities
206 2
193 2
Ameren Illinois Company |
Fuel Oils |
Other Current Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
0 
0 
Ameren Illinois Company |
Fuel Oils |
Other 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 |
Natural Gas |
Other Current Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
1 
11 
Ameren Illinois Company |
Natural Gas |
Other Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
1 
2 
Ameren Illinois Company |
Natural Gas |
Other Current Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
8 
3 
Ameren Illinois Company |
Natural Gas |
Other Deferred Credits And Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
6 
5 
Ameren Illinois Company |
Power |
Other Current Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
0 
0 
Ameren Illinois Company |
Power |
Other Assets
 
 
Derivative [Line Items]
 
 
Derivative assets
0 
 
Ameren Illinois Company |
Power |
Other Current Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
13 
12 
Ameren Illinois Company |
Power |
Other Deferred Credits And Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
179 
173 
Ameren Illinois Company |
Uranium |
Other Deferred Credits And Liabilities
 
 
Derivative [Line Items]
 
 
Derivative liabilities
$ 0 
$ 0 
Fair Value Measurements (Schedule Of Valuation Process And Unobservable Inputs) (Detail) (USD $)
In Millions, unless otherwise specified
9 Months Ended 12 Months Ended
Sep. 30, 2017
Dec. 31, 2016
Natural Gas
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative assets
$ 0 1
 
Natural Gas |
Discounted Cash Flow |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
0.34% 2 3
0.13% 2 3
Nodal basis
(1.1)4
(0.8)4
Credit risk
0.37% 2 3
0.38% 2 3
Natural Gas |
Discounted Cash Flow |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
6.00% 2 3
8.00% 2 3
Nodal basis
(0.1)4
0 4
Credit risk
0.37% 2 3
0.38% 2 3
Natural Gas |
Discounted Cash Flow |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
0.73% 2 3
1.00% 2 3
Nodal basis
(0.8)4
(0.5)4
Credit risk
0.37% 2 3
0.38% 2 3
Natural Gas |
Option Model |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
 
31.00% 4
Nodal basis
 
(0.40)4
Natural Gas |
Option Model |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
 
66.00% 4
Nodal basis
 
(0.1)4
Natural Gas |
Option Model |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
 
36.00% 4
Nodal basis
 
(0.20)4
Natural Gas |
Derivative Assets
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative assets
0 1
1 1
Natural Gas |
Derivative Liabilities
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative liabilities
(2)1
(1)1
Fuel Oils |
Discounted Cash Flow |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Escalation rate
 
(2.00%)4 5
Counterparty credit risk
0.12% 2 3
0.13% 2 3
Credit risk
0.37% 2 3
0.38% 2 3
Fuel Oils |
Discounted Cash Flow |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Escalation rate
 
2.00% 4 5
Counterparty credit risk
0.22% 2 3
0.22% 2 3
Credit risk
0.37% 2 3
0.38% 2 3
Fuel Oils |
Discounted Cash Flow |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Escalation rate
 
0.00% 4 5
Counterparty credit risk
0.17% 2 3
0.15% 2 3
Credit risk
0.37% 2 3
0.38% 2 3
Fuel Oils |
Option Model |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
24.00% 4
24.00% 4
Fuel Oils |
Option Model |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
32.00% 4
66.00% 4
Fuel Oils |
Option Model |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
26.00% 4
28.00% 4
Fuel Oils |
Derivative Assets
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative assets
1 1
1 1
Fuel Oils |
Derivative Liabilities
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative liabilities
(1)1
0 1
Power |
Discounted Cash Flow |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
0.28% 2 3
 
Nodal basis
(3)6
(6)6
Credit risk
0.37% 2 3
0.38% 2 3
Average forward peak and off-peak pricing
25 6
26 6
Estimated auction price
(324)4
(71)4
Power |
Discounted Cash Flow |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
0.28% 2 3
 
Nodal basis
0 6
0 6
Credit risk
0.37% 2 3
0.38% 2 3
Average forward peak and off-peak pricing
41 6
44 6
Estimated auction price
1,194 4
5,270 4
Power |
Discounted Cash Flow |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Counterparty credit risk
0.28% 2 3
 
Nodal basis
(2)6
(2)6
Credit risk
0.37% 2 3
0.38% 2 3
Average forward peak and off-peak pricing
28 6
29 6
Estimated auction price
269 4
125 4
Power |
Fundamental Energy Production Model |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Escalation rate
3.00% 4 7
5.00% 4 7
Estimated future gas prices
3 4
3 4
Power |
Fundamental Energy Production Model |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Escalation rate
3.00% 4 7
5.00% 4 7
Estimated future gas prices
4 4
4 4
Power |
Fundamental Energy Production Model |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Escalation rate
3.00% 4 7
5.00% 4 7
Estimated future gas prices
3 4
3 4
Power |
Contract Price Allocation |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Estimated renewable energy credit costs
5 4
5 4
Power |
Contract Price Allocation |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Estimated renewable energy credit costs
7 4
7 4
Power |
Contract Price Allocation |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Estimated renewable energy credit costs
6 4
6 4
Power |
Derivative Assets
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative assets
11 1 8
9 1 8
Power |
Derivative Liabilities
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative liabilities
(193)1 8
(187)1 8
Uranium |
Discounted Cash Flow |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Credit risk
 
0.38% 2 3
Average forward pricing
 
22 4
Uranium |
Discounted Cash Flow |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Credit risk
 
0.38% 2 3
Average forward pricing
 
24 4
Uranium |
Discounted Cash Flow |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Credit risk
 
0.38% 2 3
Average forward pricing
 
22 4
Uranium |
Option Model |
Minimum
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
 
24.00% 4
Uranium |
Option Model |
Maximum
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
 
24.00% 4
Uranium |
Option Model |
Weighted Average
 
 
Fair Value Inputs [Abstract]
 
 
Volatilities
 
24.00% 4
Uranium |
Derivative Assets
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative assets
 
0 1
Uranium |
Derivative Liabilities
 
 
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
 
 
Derivative liabilities
 
$ (4)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
Sep. 30, 2017
Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
$ 672 
$ 605 1
Assets fair value
688 2
632 2
Excluded receivables, payables, and accrued income, net
 
2 
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
672 
605 1
Assets fair value
686 2
619 2
Excluded receivables, payables, and accrued income, net
2 
(1)
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
16 2
27 2
Derivative liabilities
216 2
211 2
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
14 2
14 2
Derivative liabilities
10 2
18 2
Commodity Contract |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
206 2
193 2
Natural Gas
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 2
 
Cash and cash equivalents
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
2 
1 
Cash and cash equivalents |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
2 
1 
Equity Securities |
U.S. large capitalization
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
445 
408 
Equity Securities |
U.S. large capitalization |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
445 
408 
Debt Securities |
Corporate bonds
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
82 
67 
Debt Securities |
Corporate bonds |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
82 
67 
Debt Securities |
US treasury and government securities
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
119 
112 
Debt Securities |
US treasury and government securities |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
119 
112 
Debt Securities |
Other Debt Securities
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
24 
17 
Debt Securities |
Other Debt Securities |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
24 
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
447 
409 
Assets fair value
450 2
413 2
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
447 
409 
Assets fair value
449 2
411 2
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
3 2
4 2
Derivative liabilities
1 2
5 2
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
2 2
2 2
Derivative liabilities
1 2
5 2
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 2
0 2
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
2 
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
2 
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
445 
408 
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
445 
408 
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
225 
196 
Assets fair value
226 2
208 2
Significant Other Observable Inputs (Level 2) |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
225 
196 
Assets fair value
225 2
197 2
Significant Other Observable Inputs (Level 2) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
1 2
12 2
Derivative liabilities
19 2
14 2
Significant Other Observable Inputs (Level 2) |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 2
1 2
Derivative liabilities
7 2
7 2
Significant Other Observable Inputs (Level 2) |
Commodity Contract |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
12 2
7 2
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
82 
67 
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
82 
67 
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
119 
112 
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
119 
112 
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
24 
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
24 
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
12 2
11 2
Significant Other Unobservable Inputs (Level 3) |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Assets fair value
12 2
11 2
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
12 2
11 2
Derivative liabilities
196 2
192 2
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
12 2
11 2
Derivative liabilities
2 2
6 2
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
194 2
186 2
Significant Other Unobservable Inputs (Level 3) |
Cash and cash equivalents
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Significant Other Unobservable Inputs (Level 3) |
Cash and cash equivalents |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Significant Other Unobservable Inputs (Level 3) |
Equity Securities |
U.S. large capitalization
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Significant Other Unobservable Inputs (Level 3) |
Equity Securities |
U.S. large capitalization |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Significant Other Unobservable Inputs (Level 3) |
Debt Securities |
Corporate bonds
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Significant Other Unobservable Inputs (Level 3) |
Debt Securities |
Corporate bonds |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Significant Other Unobservable Inputs (Level 3) |
Debt Securities |
US treasury and government securities
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Significant Other Unobservable Inputs (Level 3) |
Debt Securities |
US treasury and government securities |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Significant Other Unobservable Inputs (Level 3) |
Debt Securities |
Other Debt Securities
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Significant Other Unobservable Inputs (Level 3) |
Debt Securities |
Other Debt Securities |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Nuclear Decommissioning Trust Fund
0 
0 
Uranium |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
 
4 2
Uranium |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
 
4 2
Uranium |
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
 
0 2
Uranium |
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
 
0 2
Uranium |
Significant Other Observable Inputs (Level 2) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
 
0 2
Uranium |
Significant Other Observable Inputs (Level 2) |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
 
0 2
Uranium |
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
 
4 2
Uranium |
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
 
4 2
Fuel Oils |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
3 2
3 2
Derivative liabilities
2 2
5 2
Fuel Oils |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
3 2
3 2
Derivative liabilities
2 2
5 2
Fuel Oils |
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
2 2
2 2
Derivative liabilities
1 2
5 2
Fuel Oils |
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
2 2
2 2
Derivative liabilities
1 2
5 2
Fuel Oils |
Significant Other Observable Inputs (Level 2) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 2
0 2
Derivative liabilities
0 2
0 2
Fuel Oils |
Significant Other Observable Inputs (Level 2) |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 2
0 2
Derivative liabilities
0 2
0 2
Fuel Oils |
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
1 2
1 2
Derivative liabilities
1 2
0 2
Fuel Oils |
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
1 2
1 2
Derivative liabilities
1 2
0 2
Power |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
11 2
9 2
Derivative liabilities
193 2
188 2
Power |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
11 2
9 2
Derivative liabilities
1 2
3 2
Power |
Commodity Contract |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
192 2
185 2
Power |
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 2
0 2
Derivative liabilities
0 2
0 2
Power |
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 2
0 2
Derivative liabilities
0 2
0 2
Power |
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
0 2
0 2
Power |
Significant Other Observable Inputs (Level 2) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 2
0 2
Derivative liabilities
0 2
1 2
Power |
Significant Other Observable Inputs (Level 2) |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 2
0 2
Derivative liabilities
0 2
1 2
Power |
Significant Other Observable Inputs (Level 2) |
Commodity Contract |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
0 2
0 2
Power |
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
11 2
9 2
Derivative liabilities
193 2
187 2
Power |
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
11 2
9 2
Derivative liabilities
1 2
2 2
Power |
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative liabilities
192 2
185 2
Natural Gas |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
2 2
15 2
Derivative liabilities
21 2
14 2
Natural Gas |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
 
2 2
Derivative liabilities
7 2
6 2
Natural Gas |
Commodity Contract |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
2 2
13 2
Derivative liabilities
14 2
8 2
Natural Gas |
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
1 2
2 2
Derivative liabilities
0 2
0 2
Natural Gas |
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
 
0 2
Derivative liabilities
0 2
0 2
Natural Gas |
Quoted Prices In Active Markets For Identical Assets or Liabilities (Level 1) |
Commodity Contract |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
1 2
2 2
Derivative liabilities
0 2
0 2
Natural Gas |
Significant Other Observable Inputs (Level 2) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
1 2
12 2
Derivative liabilities
19 2
13 2
Natural Gas |
Significant Other Observable Inputs (Level 2) |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
 
1 2
Derivative liabilities
7 2
6 2
Natural Gas |
Significant Other Observable Inputs (Level 2) |
Commodity Contract |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
1 2
11 2
Derivative liabilities
12 2
7 2
Natural Gas |
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
 
1 2
Derivative liabilities
2 2
1 2
Natural Gas |
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
 
1 2
Derivative liabilities
0 2
0 2
Natural Gas |
Significant Other Unobservable Inputs (Level 3) |
Commodity Contract |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Derivative assets
0 2
0 2
Derivative liabilities
$ 2 2
$ 1 2
Fair Value Measurements (Schedule Of Changes In The Fair Value Of Financial Assets And Liabilities Classified As Level Three In The Fair Value Hierarchy) (Detail) (Power, USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Jun. 30, 2017
Dec. 31, 2016
Jun. 30, 2016
Dec. 31, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
 
 
 
 
 
 
 
 
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs
$ (182)
$ (163)
$ (182)
$ (163)
$ (178)
$ (178)
$ (155)
$ (154)
Included in regulatory assets/liabilities
(5)
(6)
(17)
(17)
 
 
 
 
Purchases
 
 
15 
13 
 
 
 
 
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales
1 
 
1 
 
 
 
 
 
Settlements
0 
(2)
(3)
(5)
 
 
 
 
Change in unrealized gains (losses) related to assets/liabilities held at period end
(2)
(2)
(15)
(7)
 
 
 
 
Union Electric Company
 
 
 
 
 
 
 
 
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
 
 
 
 
 
 
 
 
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs
10 
9 
10 
9 
14 
7 
14 
16 
Included in regulatory assets/liabilities
(2)
0 
(3)
(4)
 
 
 
 
Purchases
 
 
15 
13 
 
 
 
 
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales
1 
 
1 
 
 
 
 
 
Settlements
(3)
(5)
(10)
(16)
 
 
 
 
Change in unrealized gains (losses) related to assets/liabilities held at period end
0 
0 
0 
0 
 
 
 
 
Ameren Illinois Company
 
 
 
 
 
 
 
 
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
 
 
 
 
 
 
 
 
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs
(192)
(172)
(192)
(172)
(192)
(185)
(169)
(170)
Included in regulatory assets/liabilities
(3)
(6)
(14)
(13)
 
 
 
 
Purchases
 
 
0 
0 
 
 
 
 
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales
0 
 
0 
 
 
 
 
 
Settlements
3 
3 
7 
11 
 
 
 
 
Change in unrealized gains (losses) related to assets/liabilities held at period end
$ (2)
$ (2)
$ (15)
$ (7)
 
 
 
 
Fair Value Measurements (Schedule Of Carrying Amounts And Estimated Fair Values Of Long-Term Debt And Preferred Stock) (Detail) (USD $)
In Millions, unless otherwise specified
Sep. 30, 2017
Dec. 31, 2016
Fair Value
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Long-term debt (including current portion)
$ 8,234 1
$ 7,772 1
Preferred stock
131 1
131 1
Fair Value |
Union Electric Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Long-term debt (including current portion)
4,312 
4,304 
Preferred stock
79 
79 
Fair Value |
Ameren Illinois Company
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Long-term debt (including current portion)
2,759 
2,765 
Preferred stock
52 
52 
Carrying Amount
 
 
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
 
 
Long-term debt (including current portion)
7,699 1
7,276 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)
3,967 
3,994 
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)
2,590 
2,588 
Preferred stock
$ 62 
$ 62 
Related Party Transactions Narrative (Details) (April 2017 Procurement, Ameren Illinois Company, Ameren Illinois Power Supply Agreements with Ameren Missouri)
9 Months Ended
Sep. 30, 2017
MWh
April 2017 Procurement |
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
85,600 
Long-term Contract for Purchase of Electric Power, Related Party Contract, Fixed Power, Rate
34 
Commitments And Contingencies (Other Obligations) (Detail) (USD $)
In Millions, unless otherwise specified
9 Months Ended
Sep. 30, 2017
MWh
Long-term Purchase Commitment [Line Items]
 
2017
$ 339 1
2018
951 1
2019
637 1
2020
269 1
2021
141 1
Thereafter
312 1
Total
2,649 1
Union Electric Company
 
Long-term Purchase Commitment [Line Items]
 
2017
216 
2018
610 
2019
446 
2020
174 
2021
116 
Thereafter
244 
Total
1,806 
Ameren Illinois Company
 
Long-term Purchase Commitment [Line Items]
 
2017
123 
2018
341 
2019
191 
2020
95 
2021
25 
Thereafter
45 
Total
820 
Coal
 
Long-term Purchase Commitment [Line Items]
 
2017
162 1
2018
453 1
2019
356 1
2020
79 1
2021
27 1
Thereafter
0 1
Total
1,077 1
Coal |
Union Electric Company
 
Long-term Purchase Commitment [Line Items]
 
2017
162 
2018
453 
2019
356 
2020
79 
2021
27 
Thereafter
0 
Total
1,077 
Natural Gas
 
Long-term Purchase Commitment [Line Items]
 
2017
65 1 2
2018
200 1 2
2019
148 1 2
2020
94 1 2
2021
36 1 2
Thereafter
47 1 2
Total
590 1 2
Natural Gas |
Union Electric Company
 
Long-term Purchase Commitment [Line Items]
 
2017
14 2
2018
42 2
2019
34 2
2020
26 2
2021
13 2
Thereafter
22 2
Total
151 2
Natural Gas |
Ameren Illinois Company
 
Long-term Purchase Commitment [Line Items]
 
2017
51 2
2018
158 2
2019
114 2
2020
68 2
2021
23 2
Thereafter
25 2
Total
439 2
Nuclear Fuel
 
Long-term Purchase Commitment [Line Items]
 
2017
19 1
2018
67 1
2019
27 1
2020
39 1
2021
45 1
Thereafter
58 1
Total
255 1
Nuclear Fuel |
Union Electric Company
 
Long-term Purchase Commitment [Line Items]
 
2017
19 
2018
67 
2019
27 
2020
39 
2021
45 
Thereafter
58 
Total
255 
Purchased Power
 
Long-term Purchase Commitment [Line Items]
 
2017
59 1 3 4
2018
170 1 3 4
2019
63 1 3 4
2020
13 1 3 4
2021
2 1 3 4
Thereafter
20 1 3 4
Total
327 1 3 4
Purchased Power |
Union Electric Company
 
Long-term Purchase Commitment [Line Items]
 
2017
0 3 4
2018
0 3 4
2019
0 3 4
2020
0 3 4
2021
0 3 4
Thereafter
0 3 4
Total
0 3 4
Purchased Power |
Ameren Illinois Company
 
Long-term Purchase Commitment [Line Items]
 
2017
59 3 4
2018
170 3 4
2019
63 3 4
2020
13 3 4
2021
2 3 4
Thereafter
20 3 4
Total
327 3 4
Methane Gas
 
Long-term Purchase Commitment [Line Items]
 
2017
1 1
2018
4 1
2019
4 1
2020
5 1
2021
5 1
Thereafter
64 1
Total
83 1
Methane Gas |
Union Electric Company
 
Long-term Purchase Commitment [Line Items]
 
2017
1 
2018
4 
2019
4 
2020
5 
2021
5 
Thereafter
64 
Total
83 
Other Purchased Fuel
 
Long-term Purchase Commitment [Line Items]
 
2017
33 1
2018
57 1
2019
39 1
2020
39 1
2021
26 1
Thereafter
123 1
Total
317 1
Other Purchased Fuel |
Union Electric Company
 
Long-term Purchase Commitment [Line Items]
 
2017
20 
2018
44 
2019
25 
2020
25 
2021
26 
Thereafter
100 
Total
240 
Other Purchased Fuel |
Ameren Illinois Company
 
Long-term Purchase Commitment [Line Items]
 
2017
13 
2018
13 
2019
14 
2020
14 
2021
0 
Thereafter
0 
Total
54 
April 2017 Procurement |
Ameren Illinois Company
 
Long-term Purchase Commitment [Line Items]
 
Amount of Megawatthours
4,249,800 
Long-term Purchase Commitment, Amount
128 
September 2017 Procurement |
Ameren Illinois Company
 
Long-term Purchase Commitment [Line Items]
 
Amount of Megawatthours
1,950,200 
Long-term Purchase Commitment, Amount
$ 57 
Commitments And Contingencies (Environmental Matters) (Detail) (USD $)
In Millions, unless otherwise specified
Sep. 30, 2017
scrubber
Dec. 31, 2016
Loss Contingencies [Line Items]
 
 
Percentage of Rate Base Related to Carbon Dioxide Energy Centers
 
18.00% 
Minimum
 
 
Loss Contingencies [Line Items]
 
 
Estimated capital costs to comply with existing and known federal and state air emissions regulations
$ 425 
 
Maximum
 
 
Loss Contingencies [Line Items]
 
 
Estimated capital costs to comply with existing and known federal and state air emissions regulations
525 
 
Union Electric Company
 
 
Loss Contingencies [Line Items]
 
 
Percentage of Rate Base Related to Carbon Dioxide Energy Centers
 
34.00% 
Number of Energy Center Scrubbers
2 
 
Manufactured Gas Plant
 
 
Loss Contingencies [Line Items]
 
 
Accrual for environmental loss contingencies
184 
 
Manufactured Gas Plant |
Ameren Illinois Company
 
 
Loss Contingencies [Line Items]
 
 
Number of remediation sites
44 
 
Accrual for environmental loss contingencies
184 
 
Manufactured Gas Plant |
Ameren Illinois Company |
Minimum
 
 
Loss Contingencies [Line Items]
 
 
Estimate of possible loss
184.0 
 
Manufactured Gas Plant |
Ameren Illinois Company |
Maximum
 
 
Loss Contingencies [Line Items]
 
 
Estimate of possible loss
255.0 
 
Sauget Area Two |
Union Electric Company
 
 
Loss Contingencies [Line Items]
 
 
Accrual for environmental loss contingencies
1 
 
Sauget Area Two |
Union Electric Company |
Minimum
 
 
Loss Contingencies [Line Items]
 
 
Estimate of possible loss
1.0 
 
Sauget Area Two |
Union Electric Company |
Maximum
 
 
Loss Contingencies [Line Items]
 
 
Estimate of possible loss
$ 2.5 
 
Callaway Energy Center (Narrative) (Detail) (USD $)
In Millions, unless otherwise specified
9 Months Ended 3 Months Ended
Sep. 30, 2016
Sep. 30, 2017
Nuclear Plant
mill
Dec. 31, 2017
Subsequent Event
Nuclear Waste Matters [Line Items]
 
 
 
Number of mills charged for NWF fee
 
1 
 
Litigation Settlement, Amount
$ 24 
 
$ 3 
Annual decommissioning costs included in costs of service
 
$ 7 
 
Callaway Energy Center (Insurance Disclosure) (Detail)
9 Months Ended 9 Months Ended 9 Months Ended
Sep. 30, 2017
USD ($)
Sep. 30, 2017
EUR (€)
Sep. 30, 2017
Public Liability And Nuclear Worker Liability - American Nuclear Insurers
USD ($)
Sep. 30, 2017
Public Liability And Nuclear Worker Liability - Pool Participation
USD ($)
Sep. 30, 2017
Public Liability
USD ($)
Sep. 30, 2017
Property Damage - Nuclear Electric Insurance Ltd
USD ($)
Sep. 30, 2017
Replacement Power - Nuclear Electric Insurance Ltd
USD ($)
Sep. 30, 2017
Property Damage European Mutual Association for Nuclear Insurance
USD ($)
Sep. 30, 2017
Radiation Event
USD ($)
Sep. 30, 2017
Non-radiation event
USD ($)
Nuclear Waste Matters [Line Items]
 
 
 
 
 
 
 
 
 
 
Number of weeks of coverage after the first eight weeks of an outage
1 year 
1 year 
 
 
 
 
 
 
 
 
Maximum Coverages
 
 
$ 450,000,000 
$ 12,986,000,000 1
$ 13,436,000,000 2
$ 3,200,000,000 3
$ 490,000,000 4
$ 490,000,000 
$ 2,700,000,000 
$ 2,300,000,000 
Maximum Assessments for Single Incidents
 
 
0 
127,000,000 5
127,000,000 
29,000,000 6
7,000,000 6
 
 
 
Threshold for which a retrospective assessment for a covered loss is necessary
450,000,000 
 
 
 
 
 
 
 
 
 
Annual payment in the event of an incident at any licensed commercial reactor
19,000,000 
 
 
 
 
 
 
 
 
 
Amount of weekly indemnity coverage commencing eight weeks after power outage
4,500,000 
 
 
 
 
 
 
 
 
 
Amount of additional weekly indemnity coverage commencing after initial indemnity coverage
3,600,000 
 
 
 
 
 
 
 
 
 
Amount of weekly indemnity coverage thereafter not exceeding policy limit
 
 
 
 
 
 
490,000,000 
 
 
 
Sub-limit of for non-nuclear events
 
 
 
 
 
 
328,000,000 
 
 
 
Inflationary adjustment prescribed by most recent Price-Anderson Act renewal, in years
5 years 
5 years 
 
 
 
 
 
 
 
 
Aggregate nuclear power industry insurance policy limit for losses from terrorist attacks within twelve month period
$ 3,200,000,000 
€ 600,000,000 
 
 
 
 
 
 
 
$ 1,800,000,000 
Number Of Additional Weeks After Initial Indemnity Coverage For Power Outage
1 year 4 months 10 days 
1 year 4 months 10 days 
 
 
 
 
 
 
 
 
Retirement Benefits (Components Of Net Periodic Benefit Cost) (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Pension Plan
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Service cost
$ 24 
$ 20 
$ 70 
$ 60 
Interest cost
44 
46 
134 
138 
Expected return on plan assets
(65)
(63)
(196)
(189)
Prior service cost (benefit)
(1)
0 
(1)
0 
Actuarial loss
14 
8 
41 
24 
Net periodic benefit cost
16 1 2
11 1 2
48 1 2
33 1 2
Other Postretirement Benefit Plan, Defined Benefit
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Service cost
6 
5 
16 
15 
Interest cost
12 
12 
35 
36 
Expected return on plan assets
(19)
(18)
(56)
(54)
Prior service cost (benefit)
(2)
(1)
(4)
(3)
Actuarial loss
(2)
(3)
(5)
(8)
Net periodic benefit cost
(5)1 2
(5)1 2
(14)1 2
(14)1 2
Union Electric Company |
Pension Plan
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Net periodic benefit cost
6 1
6 1
18 1
19 1
Union Electric Company |
Other Postretirement Benefit Plan, Defined Benefit
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Net periodic benefit cost
(1)1
(1)1
(3)1
(3)1
Ameren Illinois Company |
Pension Plan
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Net periodic benefit cost
10 
6 
30 
17 
Ameren Illinois Company |
Other Postretirement Benefit Plan, Defined Benefit
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Net periodic benefit cost
$ (3)
$ (3)
$ (10)
$ (10)
Retirement Benefits (Summary Of Benefit Plan Costs Incurred) (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Pension Plan
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Defined Benefit Plan, Net Periodic Benefit Cost
$ 16 1 2
$ 11 1 2
$ 48 1 2
$ 33 1 2
Pension Plan |
Union Electric Company
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Defined Benefit Plan, Net Periodic Benefit Cost
6 1
6 1
18 1
19 1
Pension Plan |
Ameren Illinois Company
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Defined Benefit Plan, Net Periodic Benefit Cost
10 
6 
30 
17 
Pension Plan |
Other Affiliated Entities and Intercompany Eliminations
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Defined Benefit Plan, Net Periodic Benefit Cost
0 
(1)
0 
(3)
Other Postretirement Benefit Plan, Defined Benefit
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Defined Benefit Plan, Net Periodic Benefit Cost
(5)1 2
(5)1 2
(14)1 2
(14)1 2
Other Postretirement Benefit Plan, Defined Benefit |
Union Electric Company
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Defined Benefit Plan, Net Periodic Benefit Cost
(1)1
(1)1
(3)1
(3)1
Other Postretirement Benefit Plan, Defined Benefit |
Ameren Illinois Company
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Defined Benefit Plan, Net Periodic Benefit Cost
(3)
(3)
(10)
(10)
Other Postretirement Benefit Plan, Defined Benefit |
Other Affiliated Entities and Intercompany Eliminations
 
 
 
 
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
 
 
 
 
Defined Benefit Plan, Net Periodic Benefit Cost
$ (1)
$ (1)
$ (1)
$ (1)
Segment Information (Schedule Of Segment Reporting Information By Segment) (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
segment
Sep. 30, 2016
Segment Reporting Information [Line Items]
 
 
 
 
Number of Reportable Segments
 
 
4 
 
External revenues
$ 1,723 
$ 1,859 
$ 4,775 
$ 4,720 
Intersegment revenues
0 
0 
0 
0 
Net Income Attributable to Ameren Common Shareholders
288 
369 
583 
621 
Capital expenditures
525 
496 
1,523 
1,496 
Union Electric Company
 
 
 
 
Segment Reporting Information [Line Items]
 
 
 
 
Number of Reportable Segments
 
 
1 
 
Ameren Illinois Company
 
 
 
 
Segment Reporting Information [Line Items]
 
 
 
 
Number of Reportable Segments
 
 
3 
 
Ameren Illinois Company
 
 
 
 
Segment Reporting Information [Line Items]
 
 
 
 
External revenues
575 
676 
1,854 
1,895 
Intersegment revenues
0 
0 
0 
 
Net Income Available to Common Shareholder
55 
119 
191 
223 
Capital expenditures
276 
241 
760 
683 
Intersegment Eliminations
 
 
 
 
Segment Reporting Information [Line Items]
 
 
 
 
External revenues
0 
0 
0 
0 
Intersegment revenues
(26)
(31)
(78)
(80)
Net Income Available to Common Shareholder
0 
0 
0 
0 
Capital expenditures
(7)
0 
(10)
0 
Intersegment Eliminations |
Ameren Illinois Company
 
 
 
 
Segment Reporting Information [Line Items]
 
 
 
 
External revenues
0 
0 
0 
 
Intersegment revenues
(14)
(14)
(32)
(35)
Net Income Available to Common Shareholder
0 
0 
0 
 
Capital expenditures
0 
0 
0 
 
Operating Segments |
Union Electric Company
 
 
 
 
Segment Reporting Information [Line Items]
 
 
 
 
External revenues
1,104 
1,150 
2,799 
2,733 
Intersegment revenues
11 
15 
41 
40 
Net Income Available to Common Shareholder
234 
241 
359 
347 
Capital expenditures
178 
147 
533 
500 
Operating Segments |
Ameren Illinois Electric Distribution
 
 
 
 
Segment Reporting Information [Line Items]
 
 
 
 
External revenues
405 
502 
1,176 
1,210 
Intersegment revenues
0 
1 
3 
3 
Net Income Available to Common Shareholder
31 
93 
94 
122 
Capital expenditures
112 
123 
354 
359 
Operating Segments |
Ameren Illinois Gas
 
 
 
 
Segment Reporting Information [Line Items]
 
 
 
 
External revenues
111 
113 
509 
529 
Intersegment revenues
1 
1 
1 
1 
Net Income Available to Common Shareholder
2 
2 
40 
44 
Capital expenditures
71 
50 
180 
130 
Operating Segments |
Ameren Transmission
 
 
 
 
Segment Reporting Information [Line Items]
 
 
 
 
External revenues
105 
94 
293 
247 
Intersegment revenues
14 1
14 1
33 1
36 1
Net Income Available to Common Shareholder
38 2
39 2
106 2
98 2
Capital expenditures
173 
175 
463 
503 
Operating Segments |
Other
 
 
 
 
Segment Reporting Information [Line Items]
 
 
 
 
External revenues
(2)
0 
(2)
1 
Intersegment revenues
0 
0 
0 
0 
Net Income Available to Common Shareholder
(17)
(6)
(16)
10 
Capital expenditures
(2)
1 
3 
4 
Operating Segments |
Ameren Illinois Company |
Ameren Illinois Electric Distribution
 
 
 
 
Segment Reporting Information [Line Items]
 
 
 
 
External revenues
405 
503 
1,179 
1,213 
Intersegment revenues
0 
0 
0 
 
Net Income Available to Common Shareholder
31 
93 
94 
122 
Capital expenditures
112 
123 
354 
359 
Operating Segments |
Ameren Illinois Company |
Ameren Illinois Gas
 
 
 
 
Segment Reporting Information [Line Items]
 
 
 
 
External revenues
112 
114 
510 
530 
Intersegment revenues
0 
0 
0 
 
Net Income Available to Common Shareholder
2 
2 
40 
44 
Capital expenditures
71 
50 
180 
130 
Operating Segments |
Ameren Illinois Company |
Ameren Illinois Transmission
 
 
 
 
Segment Reporting Information [Line Items]
 
 
 
 
External revenues
58 
59 
165 
152 
Intersegment revenues
14 3
14 3
32 3
35 3
Net Income Available to Common Shareholder
22 
24 
57 
57 
Capital expenditures
$ 93 
$ 68 
$ 226 
$ 194