Ameren (AEE) 10-Q 5 May 23 2023 Q1 Quarterly report Financial data

Cover Page

Cover Page - shares	3 Months Ended
	Mar. 31, 2023	Apr. 28, 2023
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2023
Document Transition Report	false
Entity File Number	1-14756
Entity Registrant Name	Ameren Corporation
Entity Tax Identification Number	43-1723446
Entity Incorporation, State or Country Code	MO
Entity Address, Address Line One	1901 Chouteau Avenue
Entity Address, City or Town	St. Louis
Entity Address, State or Province	MO
Entity Address, Postal Zip Code	63103
City Area Code	(314)
Local Phone Number	621-3222
Title of 12(b) Security	Common Stock, $0.01 par value per share
Trading Symbol(s)	AEE
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Emerging growth company	false
Entity Shell Company	false
Shares outstanding		262,609,472
Entity Central Index Key	0001002910
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q1
Amendment Flag	false
Union Electric Company
Entity Information [Line Items]
Entity File Number	1-2967
Entity Registrant Name	Union Electric Company
Entity Tax Identification Number	43-0559760
Entity Incorporation, State or Country Code	MO
Entity Address, Address Line One	1901 Chouteau Avenue
Entity Address, City or Town	St. Louis
Entity Address, State or Province	MO
Entity Address, Postal Zip Code	63103
City Area Code	(314)
Local Phone Number	621-3222
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Emerging growth company	false
Entity Shell Company	false
Shares outstanding		102,123,834
Entity Central Index Key	0000100826
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q1
Amendment Flag	false
Ameren Illinois Company
Entity Information [Line Items]
Entity File Number	1-3672
Entity Registrant Name	Ameren Illinois Company
Entity Tax Identification Number	37-0211380
Entity Incorporation, State or Country Code	IL
Entity Address, Address Line One	10 Richard Mark Way
Entity Address, City or Town	Collinsville
Entity Address, State or Province	IL
Entity Address, Postal Zip Code	62234
City Area Code	(618)
Local Phone Number	343-8150
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Emerging growth company	false
Entity Shell Company	false
Shares outstanding		25,452,373
Entity Central Index Key	0000018654
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q1
Amendment Flag	false

Consolidated Statement of Incom

Consolidated Statement of Income (Loss) and Comprehensive Income - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Operating Revenues:
Total operating revenues	$ 2,062	$ 1,879
Operating Expenses:
Fuel	113	176
Purchased power	495	177
Natural gas purchased for resale	208	293
Other operations and maintenance	448	461
Depreciation and amortization	320	299
Taxes other than income taxes	127	142
Total operating expenses	1,711	1,548
Operating Income	351	331
Other Income, Net	78	60
Interest Charges	127	104
Income Before Income Taxes	302	287
Income Taxes	37	34
Net Income	265	253
Less: Net Income Attributable to Noncontrolling Interests	1	1
Net Income Attributable to Ameren Common Shareholders	264	252
Pension and other postretirement benefit plan activity, net of income taxes (benefit)	(1)	1
Comprehensive Income	264	254
Less: Comprehensive Income Attributable to Noncontrolling Interests	1	1
Comprehensive Income Attributable to Ameren Common Shareholders	$ 263	$ 253
Earnings Per Share, Basic and Diluted [Abstract]
Earnings per Common Share – Basic	$ 1.01	$ 0.98
Earnings per Common Share – Diluted	$ 1	$ 0.97
Weighted-average Common Shares Outstanding – Basic	262.2	257.9
Weighted-average Common Shares Outstanding – Diluted	263.1	259
Electric
Operating Revenues:
Total operating revenues	$ 1,590	$ 1,318
Natural gas
Operating Revenues:
Total operating revenues	472	561
Union Electric Company
Operating Revenues:
Total operating revenues	923	818
Operating Expenses:
Fuel	113	176
Purchased power	208	50
Natural gas purchased for resale	47	46
Other operations and maintenance	239	232
Depreciation and amortization	176	164
Taxes other than income taxes	80	85
Total operating expenses	863	753
Operating Income	60	65
Other Income, Net	19	23
Interest Charges	51	39
Income Before Income Taxes	28	49
Income Taxes	(1)	(2)
Net Income	29	51
Preferred Stock Dividends	1	1
Net Income Attributable to Parent	28	50
Union Electric Company | Electric
Operating Revenues:
Total operating revenues	841	738
Union Electric Company | Natural gas
Operating Revenues:
Total operating revenues	82	80
Ameren Illinois Company
Operating Revenues:
Total operating revenues	1,101	1,024
Operating Expenses:
Purchased power	287	131
Natural gas purchased for resale	161	247
Other operations and maintenance	202	223
Depreciation and amortization	133	124
Taxes other than income taxes	42	53
Total operating expenses	825	778
Operating Income	276	246
Other Income, Net	37	24
Interest Charges	47	42
Income Before Income Taxes	266	228
Income Taxes	68	59
Net Income	198	169
Net Income Attributable to Parent	198	169
Ameren Illinois Company | Electric
Operating Revenues:
Total operating revenues	710	543
Ameren Illinois Company | Natural gas
Operating Revenues:
Total operating revenues	$ 391	$ 481

Consolidated Statement of Inc_2

Consolidated Statement of Income (Loss) and Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Income Statement [Abstract]
Pension and other postretirement benefit plan activity, tax	$ 0	$ 0

Consolidated Balance Sheet

Consolidated Balance Sheet - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Current Assets:
Cash and cash equivalents	$ 10	$ 10
Accounts receivable - trade (less allowance for doubtful accounts)	625	600
Unbilled revenue	299	446
Miscellaneous accounts receivable	62	54
Inventories	630	667
Current regulatory assets	292	354
Current collateral assets	29	142
Other current assets	115	155
Total current assets	2,062	2,668
Property, Plant, and Equipment, Net	31,735	31,262
Investments and Other Assets:
Nuclear decommissioning trust fund	1,019	958
Goodwill	411	411
Regulatory assets	1,599	1,426
Pension and other postretirement benefits	423	411
Other assets	815	768
Total investments and other assets	4,267	3,974
TOTAL ASSETS	38,064	37,904
Current Liabilities:
Current maturities of long-term debt	100	340
Short-term debt	1,248	1,070
Accounts and wages payable	664	1,159
Other current liabilities	745	797
Total current liabilities	2,757	3,366
Long-term Debt, Net	14,181	13,685
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes and tax credits, net	3,856	3,804
Regulatory liabilities	5,395	5,309
Asset retirement obligations	769	763
Other deferred credits and liabilities	370	340
Total deferred credits and other liabilities	10,390	10,216
Commitments and Contingencies
Shareholders’ Equity:
Common Stock	3	3
Other paid-in capital, principally premium on common stock	6,861	6,860
Retained earnings	3,745	3,646
Accumulated other comprehensive loss	(2)	(1)
Total shareholders’ equity	10,607	10,508
Noncontrolling Interests	129	129
Total equity	10,736	10,637
TOTAL LIABILITIES AND EQUITY	38,064	37,904
Investments in industrial development revenue bonds	0	240
Union Electric Company
Current Assets:
Cash and cash equivalents	3	0
Accounts receivable - trade (less allowance for doubtful accounts)	205	244
Accounts receivable – affiliates	70	51
Unbilled revenue	148	184
Miscellaneous accounts receivable	18	18
Inventories	475	434
Current regulatory assets	194	254
Current collateral assets	29	101
Other current assets	40	66
Total current assets	1,182	1,592
Property, Plant, and Equipment, Net	16,326	16,124
Investments and Other Assets:
Nuclear decommissioning trust fund	1,019	958
Regulatory assets	628	594
Pension and other postretirement benefits	102	98
Other assets	136	140
Total investments and other assets	1,885	1,790
TOTAL ASSETS	19,393	19,506
Current Liabilities:
Current maturities of long-term debt	0	240
Short-term debt	197	329
Accounts and wages payable	294	606
Accounts payable – affiliates	36	43
Taxes accrued	76	29
Interest accrued	50	63
Other current liabilities	187	260
Total current liabilities	840	1,570
Long-term Debt, Net	6,341	5,846
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes and tax credits, net	2,003	1,982
Regulatory liabilities	2,934	2,871
Asset retirement obligations	765	759
Other deferred credits and liabilities	55	51
Total deferred credits and other liabilities	5,757	5,663
Commitments and Contingencies
Shareholders’ Equity:
Common Stock	511	511
Other paid-in capital, principally premium on common stock	2,725	2,725
Preferred stock	80	80
Retained earnings	3,139	3,111
Total shareholders’ equity	6,455	6,427
TOTAL LIABILITIES AND EQUITY	19,393	19,506
Investments in industrial development revenue bonds	0	240
Ameren Illinois Company
Current Assets:
Cash and cash equivalents	0	0
Accounts receivable - trade (less allowance for doubtful accounts)	406	341
Accounts receivable – affiliates	14	12
Unbilled revenue	151	262
Miscellaneous accounts receivable	32	23
Inventories	155	233
Current regulatory assets	89	87
Other current assets	36	98
Total current assets	883	1,056
Property, Plant, and Equipment, Net	13,602	13,353
Investments and Other Assets:
Goodwill	411	411
Regulatory assets	954	821
Pension and other postretirement benefits	324	318
Other assets	510	482
Total investments and other assets	2,199	2,032
TOTAL ASSETS	16,684	16,441
Current Liabilities:
Current maturities of long-term debt	100	100
Short-term debt	324	264
Accounts and wages payable	304	451
Accounts payable – affiliates	117	93
Other current liabilities	398	383
Total current liabilities	1,243	1,291
Long-term Debt, Net	4,736	4,735
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes and tax credits, net	1,744	1,699
Regulatory liabilities	2,334	2,313
Other deferred credits and liabilities	261	235
Total deferred credits and other liabilities	4,339	4,247
Commitments and Contingencies
Shareholders’ Equity:
Common Stock	0	0
Other paid-in capital, principally premium on common stock	2,929	2,929
Preferred stock	49	49
Retained earnings	3,388	3,190
Total shareholders’ equity	6,366	6,168
TOTAL LIABILITIES AND EQUITY	$ 16,684	$ 16,441

Consolidated Balance Sheet (Par

Consolidated Balance Sheet (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Accounts Receivable, Allowance for Credit Loss, Current	$ 34	$ 31
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	400,000,000	400,000,000
Common Stock, Shares, Outstanding	262,600,000	262,000,000
Union Electric Company
Accounts Receivable, Allowance for Credit Loss, Current	$ 12	$ 13
Common stock, par value (in dollars per share)	$ 5	$ 5
Common stock, shares authorized (in shares)	150,000,000	150,000,000
Common Stock, Shares, Outstanding	102,100,000	102,100,000
Ameren Illinois Company
Accounts Receivable, Allowance for Credit Loss, Current	$ 22	$ 18
Common stock, no par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized (in shares)	45,000,000	45,000,000
Common Stock, Shares, Outstanding	25,500,000	25,500,000

Consolidated Statement of Cash

Consolidated Statement of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Cash Flows From Operating Activities:
Net income	$ 265	$ 253
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	350	324
Amortization of nuclear fuel	19	22
Amortization of debt issuance costs and premium/discounts	3	4
Deferred income taxes and investment tax credits, net	35	31
Allowance for equity funds used during construction	(9)	(8)
Stock-based compensation costs	8	4
Other	(6)	11
Changes in assets and liabilities:
Receivables	112	(117)
Inventories	37	72
Accounts and wages payable	(362)	(235)
Taxes accrued	50	47
Regulatory assets and liabilities	(40)	75
Assets, other	(14)	(10)
Liabilities, other	(6)	(39)
Pension and other postretirement benefits	(58)	(15)
Counterparty collateral, net	112	(31)
Net cash provided by operating activities	496	388
Cash Flows From Investing Activities:
Capital expenditures	(931)	(774)
Nuclear fuel expenditures	(20)	(16)
Purchases of securities – nuclear decommissioning trust fund	(29)	(97)
Sales and maturities of securities – nuclear decommissioning trust fund	17	92
Other	(1)	15
Net cash used in investing activities	(964)	(780)
Cash Flows From Financing Activities:
Dividends on common stock	(165)	(152)
Dividends paid to noncontrolling interest holders	(1)	(1)
Short-term debt, net	179	555
Issuances of long-term debt	499	0
Issuances of common stock	5	5
Employee payroll taxes related to stock-based compensation	(20)	(16)
Debt issuance costs	(5)	0
Other	(3)	0
Net cash provided by financing activities	489	391
Net change in cash, cash equivalents, and restricted cash	21	(1)
Cash, cash equivalents, and restricted cash at beginning of year	216	155
Cash, cash equivalents, and restricted cash at end of period	237	154
Union Electric Company
Cash Flows From Operating Activities:
Net income	29	51
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	205	189
Amortization of nuclear fuel	19	22
Amortization of debt issuance costs and premium/discounts	2	1
Deferred income taxes and investment tax credits, net	15	4
Allowance for equity funds used during construction	(4)	(4)
Other	(3)	0
Changes in assets and liabilities:
Receivables	74	7
Inventories	(41)	5
Accounts and wages payable	(238)	(201)
Taxes accrued	38	41
Regulatory assets and liabilities	14	(3)
Assets, other	2	10
Liabilities, other	(11)	(23)
Pension and other postretirement benefits	(21)	(4)
Counterparty collateral, net	73	(39)
Net cash provided by operating activities	153	56
Cash Flows From Investing Activities:
Capital expenditures	(481)	(414)
Nuclear fuel expenditures	(20)	(16)
Purchases of securities – nuclear decommissioning trust fund	(29)	(97)
Sales and maturities of securities – nuclear decommissioning trust fund	17	92
Other	0	18
Net cash used in investing activities	(513)	(417)
Cash Flows From Financing Activities:
Dividends on preferred stock	(1)	(1)
Short-term debt, net	(132)	363
Issuances of long-term debt	499	0
Debt issuance costs	(5)	0
Other	(3)	0
Net cash provided by financing activities	358	362
Net change in cash, cash equivalents, and restricted cash	(2)	1
Cash, cash equivalents, and restricted cash at beginning of year	13	8
Cash, cash equivalents, and restricted cash at end of period	11	9
Ameren Illinois Company
Cash Flows From Operating Activities:
Net income	198	169
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	133	124
Amortization of debt issuance costs and premium/discounts	1	3
Deferred income taxes and investment tax credits, net	37	27
Allowance for equity funds used during construction	(4)	(4)
Other	6	2
Changes in assets and liabilities:
Receivables	26	(126)
Inventories	78	67
Accounts and wages payable	(112)	(18)
Taxes accrued	25	32
Regulatory assets and liabilities	(52)	79
Assets, other	(8)	(18)
Liabilities, other	30	5
Pension and other postretirement benefits	(24)	(8)
Counterparty collateral, net	39	8
Net cash provided by operating activities	373	342
Cash Flows From Investing Activities:
Capital expenditures	(407)	(342)
Net cash used in investing activities	(407)	(342)
Cash Flows From Financing Activities:
Short-term debt, net	60	4
Net cash provided by financing activities	60	4
Net change in cash, cash equivalents, and restricted cash	26	4
Cash, cash equivalents, and restricted cash at beginning of year	191	133
Cash, cash equivalents, and restricted cash at end of period	$ 217	$ 137

Consolidated Statement of Stock

Consolidated Statement of Stockholders' Equity - USD ($) $ in Millions	Total	Common Stock	Other Paid-in Capital	Retained Earnings	Deferred Retirement Benefit Costs	Accumulated Other Comprehensive Income	Total Ameren Corporation Shareholders' Equity	Noncontrolling Interests	Union Electric Company	Union Electric Company Common Stock	Union Electric Company Other Paid-in Capital	Union Electric Company Preferred Stock	Union Electric Company Retained Earnings	Ameren Illinois Company	Ameren Illinois Company Common Stock	Ameren Illinois Company Other Paid-in Capital	Ameren Illinois Company Preferred Stock	Ameren Illinois Company Retained Earnings
Beginning of year at Dec. 31, 2021			$ 6,502	$ 3,182	$ 13			$ 129			$ 2,725		$ 2,595			$ 2,914	$ 49	$ 2,677
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under the DRPlus and 401(k) plan			13
Stock-based compensation activity			(8)
Net income	$ 253								$ 51				51	$ 169				169
Net income attributable to Ameren common shareholders	252			252
Dividends on common stock				(152)
Preferred stock dividends													(1)
Change in deferred retirement benefit costs	1				1
Net income attributable to noncontrolling interest holders	$ (1)							1
Dividends paid to noncontrolling interest holders								(1)
Common stock shares outstanding at beginning of year (in shares) at Dec. 31, 2021	257,700,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under the DRPlus and 401(k) plan	100,000
Shares issued for stock-based compensation (in shares)	400,000
Common stock shares outstanding at end of period (in shares) at Mar. 31, 2022	258,200,000
End of period at Mar. 31, 2022	$ 9,935	$ 3	6,507	3,282	14	$ 14		129		$ 511		$ 80	2,645		$ 0			2,846
Shareholders' equity, end of year at Mar. 31, 2022							$ 9,806		5,961					5,809
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per common share (in dollars per share)	$ 0.59
Beginning of year at Dec. 31, 2022	$ 10,637		6,860	3,646	(1)			129			$ 2,725		3,111			$ 2,929	$ 49	3,190
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under the DRPlus and 401(k) plan			12
Stock-based compensation activity			(11)
Net income	265								$ 29				29	$ 198				198
Net income attributable to Ameren common shareholders	264			264
Dividends on common stock				(165)
Preferred stock dividends													(1)
Change in deferred retirement benefit costs	(1)				(1)
Net income attributable to noncontrolling interest holders	$ (1)							1
Dividends paid to noncontrolling interest holders								(1)
Common stock shares outstanding at beginning of year (in shares) at Dec. 31, 2022	262,000,000								102,100,000					25,500,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under the DRPlus and 401(k) plan	100,000
Shares issued for stock-based compensation (in shares)	500,000
Common stock shares outstanding at end of period (in shares) at Mar. 31, 2023	262,600,000								102,100,000					25,500,000
End of period at Mar. 31, 2023	$ 10,736	$ 3	$ 6,861	$ 3,745	$ (2)	$ (2)		$ 129		$ 511		$ 80	$ 3,139		$ 0			$ 3,388
Shareholders' equity, end of year at Mar. 31, 2023	$ 10,607						$ 10,607		$ 6,455					$ 6,366
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per common share (in dollars per share)	$ 0.63

Summary Of Significant Accounti

Summary Of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2023
Accounting Policies [Abstract]
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 are listed below. Ameren has other subsidiaries that conduct other activities, such as providing shared services. • 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 in the MISO. Ameren’s and Ameren Missouri’s financial statements are prepared on a consolidated basis and therefore include the accounts of their majority-owned subsidiaries. All intercompany transactions have been eliminated. Ameren Missouri’s subsidiaries were created for the ownership of renewable generation projects. Ameren Illinois has no subsidiaries. All tabular dollar amounts are in millions, unless otherwise indicated. Our accounting policies conform to GAAP. Our financial statements reflect all adjustments (which include normal, recurring adjustments) that are necessary, in our opinion, for a fair presentation of our results. The preparation of financial statements in conformity with GAAP requires management to make certain estimates and assumptions. Such estimates and assumptions affect reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the dates of financial statements, and reported amounts of revenues and expenses during the reporting periods. Actual results could differ from those estimates. The results of operations for an interim period may not give a true indication of results that may be expected for a full year. These financial statements should be read in conjunction with the financial statements and accompanying notes included in the Form 10-K. Variable Interest Entities As of March 31, 2023, and December 31, 2022, Ameren had unconsolidated variable interests as a limited partner in various equity method investments, primarily to advance clean and resilient energy technologies, totaling $72 million and $68 million, respectively, included in “Other assets” on Ameren’s consolidated balance sheet. Any earnings or losses related to these investments are included in “Other Income, Net” on Ameren’s consolidated statement of income and comprehensive income. Ameren is not the primary beneficiary of these investments because it does not have the power to direct matters that most significantly affect the activities of these variable interest entities. As of March 31, 2023, the maximum exposure to loss related to these variable interests is limited to the investment in these partnerships of $72 million plus associated outstanding funding commitments of $17 million. COLI Ameren and Ameren Illinois have COLI, which is recorded at the net cash surrender value. The net cash surrender value is the amount that can be realized under the insurance policies at the balance sheet date. As of March 31, 2023, the cash surrender value of COLI at Ameren and Ameren Illinois was $254 million (December 31, 2022 – $246 million) and $120 million (December 31, 2022 – $118 million), respectively, while total borrowings against the policies were $110 million (December 31, 2022 – $110 million) at both Ameren and Ameren Illinois. Ameren and Ameren Illinois have the right to offset the borrowings against the cash surrender value of the policies and, consequently, present the net asset in “Other assets” on their respective balance sheets. The net cash surrender value of Ameren’s COLI is affected by the investment performance of a separate account in which Ameren holds a beneficial interest.

Rate And Regulatory Matters

Rate And Regulatory Matters	3 Months Ended
	Mar. 31, 2023
Public Utilities, General Disclosures [Abstract]
RATE AND REGULATORY MATTERS	RATE AND REGULATORY MATTERSBelow is a summary of updates to significant regulatory proceedings and related legal proceedings. See Note 2 – Rate and Regulatory Matters under Part II, Item 8, of the Form 10-K for additional information and a summary of our regulatory frameworks. We are unable to predict the ultimate outcome of these matters, the timing of final decisions of the various agencies and courts, or the impact on our results of operations, financial position, or liquidity. Missouri 2022 Electric Service Regulatory Rate Review In August 2022, Ameren Missouri filed a request with the MoPSC seeking approval to increase its annual revenues for electric service by $316 million. In April 2023, Ameren Missouri, the MoPSC staff, the MoOPC, and certain intervenors filed a nonunanimous stipulation and agreement with the MoPSC to increase Ameren Missouri’s annual revenues for electric service by $140 million. The remaining intervenors did not object to the agreement. The stipulation and agreement, which is subject to MoPSC approval, did not specify an allowed ROE, capital structure, rate base, or any rate base disallowances. The stipulation and agreement includes the continued use of the FAC and trackers for pension and postretirement benefits, uncertain income tax positions, certain excess deferred income taxes, and renewable energy standard costs that the MoPSC previously authorized in earlier electric rate orders, as well as the use of an electric property tax tracker. It also includes a tracker for future production and investment tax credits and proceeds from the sale of tax credits allowed under the IRA. For additional information regarding the property tax tracker and the IRA, see Note 2 – Rate and Regulatory Matters and Note 12 – Income Taxes under Part II, Item 8, in the Form 10-K. A decision by the MoPSC on the nonunanimous stipulation and agreement is expected by June 2023, with new rates expected to take effect on July 1, 2023. Ameren Missouri cannot predict whether the MoPSC will approve the stipulation and agreement, or, if approved, whether any application for rehearing or appeal will be filed, or the outcome if so filed. In addition, if the MoPSC does not approve the stipulation and agreement, Ameren Missouri cannot predict the level of any electric service rate change the MoPSC may approve, whether the requested regulatory recovery mechanisms will be approved, or whether any rate change that may eventually be approved will be sufficient for Ameren Missouri to recover its costs and earn a reasonable return on its investments when the rate change goes into effect. Solar Generation Facilities In 2022, Ameren Missouri, through its subsidiaries, entered into build-transfer agreements to acquire, after construction, the solar facilities below. The following table provides information with respect to each build-transfer agreement: Boomtown Solar Project (a) Huck Finn Solar Project (b) Agreement date February 2022 June 2022 Developer Invenergy Renewables, LLC EDF Renewables, Inc. Facility size 150-MW 200-MW Location Southeastern Illinois Central Missouri Status of MoPSC CCN Approved April 2023 Approved February 2023 Status of FERC approval of acquisition Expect to request by mid-2023 Received March 2023 Expected completion date (c) As early as fourth quarter 2024 As early as fourth quarter 2024 (a) The Boomtown Solar Project is expected to support Ameren Missouri’s transition to renewable energy generation and serve customers under the Renewable Solutions Program discussed below. (b) The Huck Finn Solar Project represents approximately $0.35 billion of capital expenditures and is expected to support Ameren Missouri’s compliance with the state of Missouri’s requirement of achieving 15% of retail sales from renewable energy sources, of which 2% must be derived from solar energy sources. (c) The expected completion dates may be impacted by the timing of FERC approval for the Boomtown Solar Project and potential sourcing issues resulting from a United States Department of Commerce investigation of solar panel components imported from four Southeast Asian countries initiated in March 2022 and the detention of certain solar panel components sourced from China as a result of the Uyghur Forced Labor Prevention Act that became effective in June 2022. Renewable Solutions Program The April 2023 MoPSC order approving the CCN for the Boomtown Solar Project also approved Ameren Missouri’s Renewable Solutions Program and a tariff related to participation in the program. The program will allow certain commercial, industrial, and governmental customers who enroll in the program to receive up to 100% of their energy from renewable resources. MoPSC Staff Review of Planned Rush Island Energy Center Retirement In February 2022, the MoPSC issued an order directing the MoPSC staff to review Ameren Missouri’s planned accelerated retirement of the Rush Island Energy Center as a result of the NSR and Clean Air Act Litigation discussed in Note 9 – Commitments and Contingencies. The MoPSC staff’s review includes potential impacts on the reliability and cost of Ameren Missouri’s service to its customers; Ameren Missouri’s plans to mitigate the customer impacts of the accelerated retirement; and the prudence of Ameren Missouri’s actions and decisions with regard to the Rush Island Energy Center, among other things. In April 2022, the MoPSC staff filed an initial report with the MoPSC in which the staff concluded early retirement of the Rush Island Energy Center may cause reliability concerns. The MoPSC staff is under no deadline to complete this review. Ameren Missouri is unable to predict the results of this matter. Results of the review could be used in other MoPSC proceedings, which could have a material adverse effect on the results of operations, financial position, and liquidity of Ameren and Ameren Missouri. MEEIA In March 2023, Ameren Missouri filed a proposed customer energy-efficiency plan with the MoPSC under the MEEIA. This filing proposed a three-year plan, which includes a portfolio of customer energy-efficiency programs, along with the continued use of the MEEIA rider, which allows Ameren Missouri to collect from, or refund to, customers any difference in actual MEEIA program costs and related lost electric margins and the amounts collected from customers. If the plan is approved, Ameren Missouri intends to invest $122 million annually in the proposed customer energy-efficiency programs from 2024 to 2026. In addition, Ameren Missouri requested performance incentives applicable to each plan year to earn additional revenues by achieving certain customer energy-efficiency and target spending goals. If 100% of the goals are achieved, Ameren Missouri would earn additional revenues totaling $55 million over the three-year plan. Ameren Missouri also requested additional performance incentives applicable to each plan year totaling up to $14 million over the three-year plan, if Ameren Missouri exceeds 100% of the goals. The MoPSC is under no deadline to issue an order in this proceeding. Illinois MYRP In January 2023, Ameren Illinois filed an MYRP with the ICC to be used in setting electric distribution service rates for 2024 through 2027. Under the MYRP, the ICC would approve base rates for electric distribution service to be charged to customers for each calendar year of the four-year period. The following table includes the forecasted revenue requirement, the requested ROE, the requested capital structure common equity percentage, and the forecasted average annual rate base for 2024 through 2027, as reflected in Ameren Illinois’ MYRP: Year Forecasted Revenue Requirement (in millions) Requested ROE Requested Capital Structure Common Equity Percentage (a) Forecasted Average Annual Rate Base (in billions) 2024 $1,282 10.5% 53.99% $4.3 2025 $1,373 10.5% 53.97% $4.6 2026 $1,477 10.5% 54.02% $5.0 2027 $1,556 10.5% 54.03% $5.3 (a) A capital structure of up to and including 50% common equity is deemed prudent and reasonable by law. A higher equity ratio requires specific ICC approval. Under an MYRP, the IETL permits any initial rate increase to be phased in, with at least 50% of the first annual period’s approved rate increase reflected in rates in the first annual period, with the remaining portion deferred as a regulatory asset that earns a return at the applicable WACC and is collected from customers over a period not to exceed two years beginning within one year after the second annual period’s rates are effective. Ameren Illinois’ MYRP filing utilizes this phase-in provision and proposes to defer 50% of the requested 2024 rate increase of $171 million as a regulatory asset to be collected from customers in 2026. Ameren Illinois recognizes revenues when amounts are expected to be collected from customers within two years from the end of an applicable year. An ICC decision in this proceeding is required by December 2023, with new rates effective starting in January 2024. Ameren Illinois cannot predict the level of any electric distribution service rate change the ICC may approve, or whether any rate change that may eventually be approved will be sufficient for Ameren Illinois to recover its costs to the extent those costs are subject to and exceed the reconciliation cap discussed below and earn a reasonable return on its investments when the rate change goes into effect. The MYRP also allows Ameren Illinois to reconcile its actual revenue requirement, as adjusted for certain cost variations, to ICC-approved electric distribution service rates on an annual basis, subject to a reconciliation cap. The reconciliation cap limits the annual adjustment to 105% of the annual revenue requirement approved by the ICC. Certain variations from forecasted costs would be excluded from the reconciliation cap, including those associated with major storms; new business and facility relocations; changes in the timing of certain expenditures or investments into or out of the applicable calendar year; and changes in interest rates, income taxes, taxes other than income taxes, pension and other post-retirement benefits costs, and amortization of certain assets. The reconciliation cap also excludes costs recovered through riders outside of base rates, such as riders for electric energy-efficiency investments, power procurement and transmission services, renewable energy credit compliance, zero emission credits, certain environmental costs, and bad debt write-offs, among others. Ameren Illinois’ existing riders will remain effective and electric distribution service revenues will continue to be decoupled from sales volumes under the MYRP. The actual revenue requirement for a particular year would incorporate Ameren Illinois’ year-end rate base and actual capital structure for such year, provided that the common equity ratio in such capital structure may not exceed that approved by the ICC in the MYRP. Excluding the phase-in of the initial rate increase discussed above, and subject to the reconciliation cap, if a given year’s revenue amount collected from customers varies from the approved revenue requirement, an adjustment would be made to electric operating revenues with an offset to a regulatory asset or liability to reflect that year’s actual revenue requirement, independent of actual sales volumes. The regulatory balance would then be collected from, or refunded to, customers within two years from the end of the applicable annual period. Under the MYRP, the ROE approved by the ICC will be subject to annual adjustments during the four-year period based on seven performance metrics. In 2022, the ICC issued an order approving total ROE incentives and penalties of 24 basis points, allocated among the seven performance metrics. These performance metrics include improvements in service reliability in both the frequency and duration of outages, a reduction in peak loads, an increased percentage of spend with diverse suppliers, a reduction in disconnections for certain customers, and improved timeliness in response to customer requests for interconnection of distributed energy resources. These performance metrics will apply annually from 2024 through 2027 under the MYRP, and the impact of any incentives and penalties will be excluded from the reconciliation cap described above. 2022 Electric Distribution Revenue Requirement Reconciliation Adjustment Request In April 2023, Ameren Illinois filed for a reconciliation adjustment to its 2022 electric distribution service revenue requirement with the ICC, requesting recovery of $127 million. The reconciliation adjustment reflects Ameren Illinois’ actual 2022 recoverable costs, year-end rate base, and capital structure, which was composed of 53.99% common equity. An ICC decision in this proceeding is required by December 2023, and any approved adjustment would be collected from customers in 2024. 2023 Natural Gas Delivery Service Regulatory Rate Review In January 2023, Ameren Illinois filed a request with the ICC seeking approval to increase its annual revenues for natural gas delivery service by $160 million, which included an estimated $77 million of annual revenues that would otherwise be recovered under the QIP and other riders. The request is based on a 10.7% allowed ROE, a capital structure composed of 53.99% common equity, and a rate base of $2.9 billion. In an attempt to reduce regulatory lag, Ameren Illinois used a 2024 future test year in this proceeding. A decision by the ICC in this proceeding is required by late November 2023, with new rates expected to be effective in early December 2023. Ameren Illinois cannot predict the level of any delivery service rate change the ICC may approve, nor whether any rate change that may eventually be approved will be sufficient to enable Ameren Illinois to recover its costs and to earn a reasonable return on investments when the rate changes go into effect. Federal FERC Complaint Cases Since November 2013, the allowed base ROE for FERC-regulated transmission rate base under the MISO tariff has been subject to customer complaint cases and has been changed by various FERC orders. In May 2020, the FERC issued an order, which set the allowed base ROE to 10.02%, and required refunds, with interest, for the periods November 2013 to February 2015 and from late September 2016 forward. Ameren and Ameren Illinois paid these refunds, including interest, by March 31, 2022. In June and July 2020, Ameren Missouri, Ameren Illinois, and ATXI, as well as various customers, petitioned the United States Court of Appeals for the District of Columbia Circuit for review of the May 2020 order, challenging certain aspects of the new ROE methodology established. The petition filed by Ameren Missouri, Ameren Illinois, and ATXI challenged the refunds required for the period from September 2016 to May 2020. In August 2022, the court issued a ruling that granted the customers’ petition for review, vacated the FERC’s previous MISO ROE-determining orders, and remanded the proceedings to the FERC. The court elected not to rule on the issues raised by Ameren Missouri, Ameren Illinois, and ATXI; however, they may raise the issues again in the future. The currently allowed base ROE of 10.02% will remain effective for customer billings, but is subject to refund if the base ROE is changed by the FERC in a future order. The FERC is under no deadline to issue an order related to these proceedings. A 50 basis point change in the FERC-allowed ROE would affect Ameren’s and Ameren Illinois’ annual revenue by an estimated $19 million and $13 million, respectively, based on each company’s 2023 projected rate base.

Short-Term Debt And Liquidity

Short-Term Debt And Liquidity	3 Months Ended
	Mar. 31, 2023
Debt Disclosure [Abstract]
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, and, in the case of Ameren Missouri and Ameren Illinois, short-term affiliate 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. Short-term Borrowings The Missouri Credit Agreement and the Illinois Credit Agreement are available to support issuances under Ameren (parent)’s, Ameren Missouri’s, and Ameren Illinois’ commercial paper programs, respectively, subject to borrowing sublimits, and the issuance of letters of credit. As of March 31, 2023, based on commercial paper outstanding and letters of credit issued under the Credit Agreements, along with cash and cash equivalents, the net liquidity available to Ameren (parent), Ameren Missouri, and Ameren Illinois, collectively, was $1.4 billion. The Ameren Companies were in compliance with the covenants in their Credit Agreements as of March 31, 2023. As of March 31, 2023, the ratios of consolidated indebtedness to consolidated total capitalization, calculated in accordance with the provisions of the Credit Agreements, were 59%, 51%, and 45% for Ameren, Ameren Missouri, and Ameren Illinois, respectively. The following table presents commercial paper outstanding, net of issuance discounts, as of March 31, 2023, and December 31, 2022. There were no borrowings outstanding under the Credit Agreements as of March 31, 2023, or December 31, 2022. March 31, 2023 December 31, 2022 Ameren (parent) $ 727 $ 477 Ameren Missouri 197 329 Ameren Illinois 324 264 Ameren consolidated $ 1,248 $ 1,070 The following table summarizes the activity and relevant interest rates for Ameren (parent)’s, Ameren Missouri’s, and Ameren Illinois’ commercial paper issuances and borrowings under the Credit Agreements in the aggregate for the three months ended March 31, 2023 and 2022: Ameren Ameren Ameren Ameren 2023 Average daily amount outstanding $ 506 $ 436 $ 233 $ 1,175 Weighted-average interest rate 4.89 % 4.86 % 4.89 % 4.88 % Peak amount outstanding during period (a) $ 728 $ 592 $ 325 $ 1,381 Peak interest rate 5.55 % 5.55 % 5.60 % 5.60 % 2022 Average daily amount outstanding $ 282 $ 408 $ 99 $ 789 Weighted-average interest rate 0.41 % 0.44 % 0.33 % 0.41 % Peak amount outstanding during period (a) $ 466 $ 539 $ 142 $ 1,101 Peak interest rate 1.05 % 1.06 % 1.15 % 1.15 % (a) The timing of peak outstanding commercial paper issuances and borrowings under the Credit Agreements varies by company. Therefore, the sum of individual company peak amounts may not equal the Ameren consolidated peak for the period. Money Pools Ameren has money pool agreements with and among its subsidiaries to coordinate and provide for certain short-term cash and working capital requirements. The average interest rate for borrowings under the utility money pool for the three months ended March 31, 2023, was 4.80% (2022 – 0.39%). See Note 8 – Related-party Transactions for the amount of interest income and expense from the utility money pool arrangements recorded by Ameren Missouri and Ameren Illinois for the three months ended March 31, 2023 and 2022.

Long-Term Debt And Equity Finan

Long-Term Debt And Equity Financings	3 Months Ended
	Mar. 31, 2023
Long-Term Debt And Equity Financings [Abstract]
LONG-TERM DEBT AND EQUITY FINANCINGS	LONG-TERM DEBT AND EQUITY FINANCINGS Ameren For the three months ended March 31, 2023, Ameren issued a total of 0.1 million shares of common stock under its DRPlus and 401(k) plan, and received proceeds of $5 million and had a receivable of $7 million. In addition, in the first quarter of 2023, Ameren issued 0.5 million shares of common stock valued at $37 million upon the settlement of stock-based compensation awards. There were no shares issued under the ATM program for the three months ended March 31, 2023. As of March 31, 2023, Ameren had approximately $980 million of common stock available for sale under the ATM program, which takes into account the forward sale agreements in effect as of March 31, 2023, discussed below. As of April 30, 2023, Ameren had multiple forward sale agreements that could be settled under the ATM program with various counterparties relating to 3.8 million shares of common stock. The forward sale agreements outstanding as of March 31, 2023, can be settled at Ameren’s discretion on or prior to dates ranging from January 10, 2024 to October 3, 2024. On a settlement date or dates, if Ameren elects to physically settle a forward sale agreement, Ameren will issue shares of common stock to the counterparties at the then-applicable forward sale price. The initial forward sale price for the agreements ranged from $89.31 to $94.80, with an average initial forward sale price of $92.66. Each initial forward sale price is subject to adjustment based on a floating interest rate factor equal to the overnight bank funding rate less a spread of 75 basis points, and will be subject to decrease on certain dates specified in the forward sale agreements by specified amounts related to expected dividends on shares of the common stock during the term of the forward sale agreements. If the overnight bank funding rate is less than the spread on any day, the interest rate factor will result in a reduction of the forward sale price. The forward sale agreements will be physically settled unless Ameren elects to settle in cash or to net share settle. At March 31, 2023, Ameren could have settled the forward sale agreements with physical delivery of 3.4 million shares of common stock to the respective counterparties in exchange for cash of $317 million. Alternatively, the forward sale agreements could have also been settled at March 31, 2023, with the counterparties delivering approximately $21 million of cash or approximately 0.2 million shares of common stock to Ameren. In connection with the forward sale agreements, the various counterparties, or their affiliates, borrowed from third parties and sold 3.4 million shares of common stock. The gross sales price of these shares totaled $321 million. In connection with such sales, the counterparties were deemed to have received commissions of $3 million. Ameren has not received any proceeds from such sales of borrowed shares. The forward sale agreements have been classified as equity transactions. In April 2023, Ameren entered into a forward sale agreement under the ATM program relating to 0.4 million shares of common stock. The April 2023 forward sale agreement can be settled at Ameren’s discretion on or prior to January 14, 2025. The initial forward sale price was $89.11. Ameren Missouri In January 2023, Ameren Missouri and Audrain County mutually agreed to terminate a financing obligation agreement related to the CT energy center in Audrain County, which was scheduled to expire in December 2023. No cash was exchanged in connection with the termination of the agreement as the $240 million principal amount of the financing obligation due from Ameren Missouri was equal to the amount of bond service payments due to Ameren Missouri. Ownership of the energy center was transferred to Ameren Missouri in January 2023, at which time the property, plant, and equipment became subject to the lien of the Ameren Missouri mortgage bond indenture. In March 2023, Ameren Missouri issued $500 million of 5.45% first mortgage bonds due March 2053, with interest payable semiannually on March 15 and September 15 of each year, beginning September 15, 2023. Ameren Missouri received net proceeds of $495 million, which were used for capital expenditures and to repay short-term debt. Indenture Provisions and Other Covenants 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. At March 31, 2023, 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 agreements. Off-balance-sheet Arrangements At March 31, 2023, none of the Ameren Companies had any material off-balance-sheet financing arrangements, other than Ameren’s investment in variable interest entities and the multiple forward sale agreements under the ATM program relating to common stock. See Note 1 – Summary of Significant Accounting Policies for further detail concerning variable interest entities.

Other Income, Net

Other Income, Net	3 Months Ended
	Mar. 31, 2023
Other Nonoperating Income (Expense) [Abstract]
OTHER INCOME, NET	OTHER INCOME, NET The following table presents the components of “Other Income, Net” in the Ameren Companies’ statements of income for the three months ended March 31, 2023 and 2022: Three Months 2023 2022 Ameren: Allowance for equity funds used during construction $ 9 $ 8 Interest income on industrial development revenue bonds 1 6 Non-service cost components of net periodic benefit income (a) 64 46 Miscellaneous income 9 4 Earnings related to equity method investments 2 3 Donations (2) (2) Miscellaneous expense (5) (5) Total Other Income, Net $ 78 $ 60 Ameren Missouri: Allowance for equity funds used during construction $ 4 $ 4 Interest income on industrial development revenue bonds 1 6 Non-service cost components of net periodic benefit income (a) 14 14 Miscellaneous income 4 2 Donations (1) (1) Miscellaneous expense (3) (2) Total Other Income, Net $ 19 $ 23 Ameren Illinois: Allowance for equity funds used during construction $ 4 $ 4 Non-service cost components of net periodic benefit income 31 21 Miscellaneous income 5 2 Donations (1) (1) Miscellaneous expense (2) (2) Total Other Income, Net $ 37 $ 24 (a) For the three months ended March 31, 2023 and 2022, the non-service cost components of net periodic benefit income were adjusted by amounts deferred of $17 million and $6 million, respectively, due to a regulatory tracking mechanism for the difference between the level of such costs incurred by Ameren Missouri under GAAP and the level of such costs included in rates. See Note 11– Retirement Benefits for additional information.

Derivative Financial Instrument

Derivative Financial Instruments	3 Months Ended
	Mar. 31, 2023
Derivative Instruments and Hedging Activities Disclosure [Abstract]
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; • actual cash outlays for the purchase of these commodities that differ from anticipated cash outlays; and • actual off-system sales revenues that differ from anticipated revenues. 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. 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. 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. The following disclosures exclude NPNS contracts and other non-derivative commodity contracts that are accounted for under the accrual method of accounting. 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 March 31, 2023, and December 31, 2022, all contracts that met the definition of a derivative and were not eligible for the NPNS exception received regulatory deferral. Cash flows for all derivative financial instruments are classified in cash flows from operating activities. The following table presents open gross commodity contract volumes by commodity type for derivative assets and liabilities as of March 31, 2023, and December 31, 2022. As of March 31, 2023, these contracts extended through October 2025, October 2029, May 2032 and March 2024 for fuel oils, natural gas, power and uranium, respectively. Quantity (in millions) March 31, 2023 December 31, 2022 Commodity Ameren Missouri Ameren Illinois Ameren Ameren Missouri Ameren Illinois Ameren Fuel oils (in gallons) 18 — 18 18 — 18 Natural gas (in mmbtu) 60 185 245 48 157 205 Power (in MWhs) 1 6 7 1 6 7 Uranium (pounds in thousands) 186 — 186 514 — 514 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 March 31, 2023, and December 31, 2022: March 31, 2023 December 31, 2022 Balance Sheet Location Ameren Ameren Ameren Ameren Ameren Ameren Fuel oils Other current assets $ 8 $ — $ 8 $ 13 $ — $ 13 Other assets 2 — 2 3 — 3 Natural gas Other current assets 1 5 6 7 23 30 Other assets 8 8 16 9 11 20 Power Other current assets 5 — 5 14 2 16 Other assets — 1 1 — 4 4 Uranium Other current assets 1 — 1 2 — 2 Other assets — — — 1 — 1 Total assets $ 25 $ 14 $ 39 $ 49 $ 40 $ 89 Fuel oils Other deferred credits and liabilities $ 1 $ — $ 1 $ — $ — $ — Natural gas Other current liabilities 9 33 42 7 20 27 Other deferred credits and liabilities 5 12 17 2 9 11 Power Other current liabilities 17 10 27 59 2 61 Other deferred credits and liabilities — 43 43 — 37 37 Total liabilities $ 32 $ 98 $ 130 $ 68 $ 68 $ 136 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. Th e following table p rovides the recognized gross derivative balances and the net amounts of those derivatives subject to an enforceable master netting arrangement or similar agreement as of March 31, 2023, and December 31, 2022: Gross Amounts Not Offset in the Balance Sheet Commodity Contracts Eligible to be Offset Gross Amounts Recognized in the Balance Sheet Derivative Instruments Cash Collateral Received/Posted (a) Net March 31, 2023 Assets: Ameren Missouri $ 25 $ 9 $ — $ 16 Ameren Illinois 14 11 — 3 Ameren $ 39 $ 20 $ — $ 19 Liabilities: Ameren Missouri $ 32 $ 9 $ 16 $ 7 Ameren Illinois 98 11 — 87 Ameren $ 130 $ 20 $ 16 $ 94 December 31, 2022 Assets: Ameren Missouri $ 49 $ 9 $ — $ 40 Ameren Illinois 40 20 — 20 Ameren $ 89 $ 29 $ — $ 60 Liabilities: Ameren Missouri $ 68 $ 9 $ 56 $ 3 Ameren Illinois 68 20 — 48 Ameren $ 136 $ 29 $ 56 $ 51 (a) Cash collateral received reduces gross asset balances and is included in “Other current liabilities” and “Other deferred credits and liabilities” on the balance sheet. Cash collateral posted reduces gross liability balances and is included in “Current collateral assets” and “Other assets” on the balance sheet for Ameren and Ameren Missouri and “Other current assets” and “Other assets” for Ameren Illinois. 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. As of March 31, 2023, if counterparty groups were to fail completely to perform on contracts, the Ameren Companies’ maximum exposure related to derivative assets, predominantly from financial institutions, would have been immaterial with or without consideration of the application of master netting arrangements or similar agreements and collateral held. Certain of our derivative instruments contain collateral provisions tied to the Ameren Companies’ credit ratings. If our credit ratings were downgraded below investment grade, 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 additional collateral required is the net liability position allowed under master netting arrangements or similar agreements, assuming (1) the credit risk-related contingent features underlying these arrangements were triggered and (2) those counterparties with rights to do so requested collateral. The following table presents, as of March 31, 2023, 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: Aggregate Fair Value of Derivative Liabilities (a) Cash Potential Aggregate Amount of Additional Collateral Required (b) Ameren Missouri $ 16 $ — $ 7 Ameren Illinois 45 — 36 Ameren $ 61 $ — $ 43 (a) Before consideration of master netting arrangements or similar agreements.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2023
Fair Value Disclosures [Abstract]
Fair Value Disclosures	FAIR VALUE MEASUREMENTSFair 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. Fair value measurements are classified in three levels based on the fair value hierarchy as defined by GAAP. See Note 8 – Fair Value Measurements under Part II, Item 8, of the Form 10-K for information related to hierarchy levels and valuation techniques. We consider nonperformance risk in our valuation of derivative instruments by analyzing our own credit standing and the credit standing of our counterparties, and by considering any credit enhancements (e.g., collateral). 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 material gains or losses related to valuation adjustments for counterparty default risk were recorded at Ameren, Ameren Missouri, or Ameren Illinois in the three months ended March 31, 2023 or 2022. At March 31, 2023, and December 31, 2022, 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 March 31, 2023, and December 31, 2022: March 31, 2023 December 31, 2022 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets: Ameren Missouri Derivative assets – commodity contracts: Fuel oils $ 10 $ — $ — $ 10 $ 16 $ — $ — $ 16 Natural gas — 9 — 9 1 15 — 16 Power — — 5 5 — — 14 14 Uranium — — 1 1 — — 3 3 Total derivative assets – commodity contracts $ 10 $ 9 $ 6 $ 25 $ 17 $ 15 $ 17 $ 49 Nuclear decommissioning trust fund: Equity securities: U.S. large capitalization $ 668 $ — $ — $ 668 $ 618 $ — $ — $ 618 Debt securities: U.S. Treasury and agency securities — 149 — 149 — 137 — 137 Corporate bonds — 123 — 123 — 122 — 122 Other — 74 — 74 — 70 — 70 Total nuclear decommissioning trust fund $ 668 $ 346 $ — $ 1,014 (a) $ 618 $ 329 $ — $ 947 (a) Total Ameren Missouri $ 678 $ 355 $ 6 $ 1,039 $ 635 $ 344 $ 17 $ 996 Ameren Illinois Derivative assets – commodity contracts: Natural gas $ — $ 10 $ 3 $ 13 $ 1 $ 28 $ 5 $ 34 Power — — 1 1 — — 6 6 Total Ameren Illinois $ — $ 10 $ 4 $ 14 $ 1 $ 28 $ 11 $ 40 Ameren Derivative assets – commodity contracts (b) $ 10 $ 19 $ 10 $ 39 $ 18 $ 43 $ 28 $ 89 Nuclear decommissioning trust fund (c) 668 346 — 1,014 (a) 618 329 — 947 (a) Total Ameren $ 678 $ 365 $ 10 $ 1,053 $ 636 $ 372 $ 28 $ 1,036 Liabilities: Ameren Missouri Derivative liabilities – commodity contracts: Fuel oils $ 1 $ — $ — $ 1 $ — $ — $ — $ — Natural gas — 11 3 14 — 6 3 9 Power 17 — — 17 57 — 2 59 Total Ameren Missouri $ 18 $ 11 $ 3 $ 32 $ 57 $ 6 $ 5 $ 68 Ameren Illinois Derivative liabilities – commodity contracts: Natural gas $ 1 $ 36 $ 8 $ 45 $ — $ 19 $ 10 $ 29 Power — — 53 53 — — 39 39 Total Ameren Illinois $ 1 $ 36 $ 61 $ 98 $ — $ 19 $ 49 $ 68 Ameren Derivative liabilities – commodity contracts (b) $ 19 $ 47 $ 64 $ 130 $ 57 $ 25 $ 54 $ 136 (a) Balance excludes $5 million and $11 million of cash and cash equivalents, receivables, payables, and accrued income, net, for March 31, 2023, and December 31, 2022, respectively. (b) See the Ameren Missouri and Ameren Illinois sections of the table for a breakout of the fair value of Ameren’s derivative assets and liabilities by type of commodity. (c) See the Ameren Missouri section of the table for a breakout of the fair value of Ameren’s nuclear decommissioning trust fund by investment type. Level 3 fuel oils, natural gas, and uranium derivative contract assets and liabilities measured at fair value on a recurring basis were immaterial for all periods presented. The following table presents the fair value reconciliation of Level 3 power derivative contract assets and liabilities measured at fair value on a recurring basis for the three months ended March 31, 2023 and 2022: 2023 2022 Ameren Missouri Ameren Illinois Ameren Ameren Missouri Ameren Illinois Ameren For the three months ended March 31: Beginning balance at January 1 $ 12 $ (33) $ (21) $ (15) $ (117) $ (132) Realized and unrealized gains/(losses) included in regulatory assets/liabilities (6) (20) (26) (41) 42 1 Settlements (1) 1 — 3 1 4 Ending balance at March 31 $ 5 $ (52) $ (47) $ (53) $ (74) $ (127) Change in unrealized gains/(losses) related to assets/liabilities held at March 31 $ (2) $ (18) $ (20) $ (38) $ 42 $ 4 All gains or losses related to our Level 3 derivative commodity contracts are expected to be recovered or returned through customer rates; therefore, there is no impact to either net income or other comprehensive income resulting from changes in the fair value of these instruments. The following table describes the valuation techniques and significant unobservable inputs utilized for the fair value of our Level 3 power derivative contract assets and liabilities as of March 31, 2023, and December 31, 2022: Fair Value Weighted Average (b) Commodity Assets Liabilities Valuation Technique(s) Unobservable Input (a) Range 2023 Power (c) $ 6 $ (53) Discounted cash flow Average forward peak and off-peak pricing – forwards/swaps ($/MWh) 22 – 74 46 Nodal basis ($/MWh) (9) – (1) (4) 2022 Power (d) $ 20 $ (41) Discounted cash flow Average forward peak and off-peak pricing – forwards/swaps ($/MWh) 38 – 89 51 Nodal basis ($/MWh) (10) – (1) (4) Trend rate (%) 0 1 0 (a) Generally, significant increases (decreases) in these inputs in isolation would result in a significantly higher (lower) fair value measurement. (b) Unobservable inputs were weighted by relative fair value. (c) Valuations use visible forward prices adjusted for nodal-to-hub basis differentials. (d) Valuations through 2031 use visible forward prices adjusted for nodal-to-hub basis differentials. Valuations beyond 2031 use a trend rate factor and are similarly adjusted for nodal-to-hub basis differentials. The following table sets forth the carrying amount and, by level within the fair value hierarchy, the fair value of financial assets and liabilities disclosed, but not recorded, at fair value as of March 31, 2023, and December 31, 2022: Carrying Fair Value Level 1 Level 2 Level 3 Total March 31, 2023 Ameren: Cash, cash equivalents, and restricted cash $ 237 $ 237 $ — $ — $ 237 Short-term debt 1,248 — 1,248 — 1,248 Long-term debt (including current portion) 14,281 (a) — 12,408 473 (b) 12,881 Ameren Missouri: Cash, cash equivalents, and restricted cash $ 11 $ 11 $ — $ — $ 11 Short-term debt 197 — 197 — 197 Long-term debt (including current portion) 6,341 (a) — 5,706 — 5,706 Ameren Illinois: Cash, cash equivalents, and restricted cash $ 217 $ 217 $ — $ — $ 217 Short-term debt 324 — 324 — 324 Long-term debt (including current portion) 4,836 (a) — 4,368 — 4,368 December 31, 2022 Ameren: Cash, cash equivalents, and restricted cash $ 216 $ 216 $ — $ — $ 216 Investment in industrial development revenue bonds (c) 240 — 240 — 240 Short-term debt 1,070 — 1,070 — 1,070 Long-term debt (including current portion) (c) 14,025 (a) — 11,989 464 (b) 12,453 Ameren Missouri: Cash, cash equivalents, and restricted cash $ 13 $ 13 $ — $ — $ 13 Investment in industrial development revenue bonds (c) 240 — 240 — 240 Short-term debt 329 — 329 — 329 Long-term debt (including current portion) (c) 6,086 (a) — 5,365 — 5,365 Ameren Illinois: Cash, cash equivalents, and restricted cash $ 191 $ 191 $ — $ — $ 191 Short-term debt 264 — 264 — 264 Long-term debt (including current portion) 4,835 (a) — 4,320 — 4,320 (a) Included unamortized debt issuance costs, which were excluded from the fair value measurement, of $103 million, $45 million, and $44 million for Ameren, Ameren Missouri, and Ameren Illinois, respectively, as of March 31, 2023. Included unamortized debt issuance costs, which were excluded from the fair value measurement, of $99 million, $41 million, and $44 million for Ameren, Ameren Missouri, and Ameren Illinois, respectively, as of December 31, 2022. (b) The Level 3 fair value amount consists of ATXI’s senior unsecured notes. (c) Ameren and Ameren Missouri had an investment in industrial development revenue bonds, classified as held-to-maturity and recorded in “Other Assets,” that were equal to the finance obligation for the Audrain CT energy center. As of December 31, 2022, the carrying amount of the investment in industrial development revenue bonds and the finance obligation approximated fair value.

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2023
Related Party Transactions [Abstract]
RELATED PARTY TRANSACTIONS	RELATED-PARTY TRANSACTIONS In the ordinary course of business, Ameren Missouri and Ameren Illinois have engaged in, and may in the future engage in, affiliate transactions. These transactions primarily consist of natural gas and power purchases and sales, services received or rendered, and borrowings and lendings. Transactions between Ameren’s subsidiaries are reported as affiliate transactions on their individual financial statements, but those transactions are eliminated in consolidation for Ameren’s consolidated financial statements. For a discussion of material related-party agreements and money pool arrangements, see Note 13 – Related-party Transactions and Note 4 – Short-term Debt and Liquidity under Part II, Item 8, of the Form 10-K. Support Services Agreements Ameren Missouri and Ameren Illinois had long-term receivables included in “Other assets” from Ameren Services of $36 million and $39 million, respectively, as of March 31, 2023, and $41 million and $43 million, respectively, as of December 31, 2022, related to Ameren Services’ allocated portion of Ameren’s pension and postretirement benefit plans. Tax Allocation Agreement See Note 1 – Summary of Significant Accounting Policies under Part II, Item 8, of the Form 10-K for a discussion of the tax allocation agreement. The following table presents the affiliate balances related to income taxes for Ameren Missouri and Ameren Illinois as of March 31, 2023, and December 31, 2022: March 31, 2023 December 31, 2022 Ameren Missouri Ameren Illinois Ameren Missouri Ameren Illinois Income taxes payable to parent (a) $ — $ 80 $ — $ 50 Income taxes receivable from parent (b) 54 — 39 — (a) Included in “Accounts payable – affiliates” on the balance sheet. (b) Included in “Accounts receivable – affiliates” on the balance sheet. Effects of Related-party Transactions on the Statement of Income The following table presents the impact on Ameren Missouri and Ameren Illinois of related-party transactions for the three months ended March 31, 2023 and 2022: Three Months Agreement Income Statement Ameren Ameren Ameren Missouri power supply Operating Revenues 2023 $ (b) $ (a) agreements with Ameren Illinois 2022 4 (a) Ameren Missouri and Ameren Illinois Operating Revenues 2023 $ 10 $ (b) rent and facility services 2022 6 (b) Ameren Missouri and Ameren Illinois miscellaneous Operating Revenues 2023 $ (b) $ (b) support services 2022 (b) 1 Total Operating Revenues 2023 $ 10 $ (b) 2022 10 1 Ameren Illinois power supply Purchased Power 2023 $ (a) $ (b) agreements with Ameren Missouri 2022 (a) 4 Ameren Missouri and Ameren Illinois Purchased Power 2023 $ (b) $ (b) transmission services from ATXI 2022 (b) (b) Total Purchased Power 2023 $ (b) $ (b) 2022 (b) 4 Ameren Missouri and Ameren Illinois Other Operations and Maintenance 2023 $ (b) $ 2 rent and facility services 2022 (b) 1 Ameren Services support services Other Operations and Maintenance 2023 $ 35 $ 35 agreement 2022 38 35 Total Other Operations and 2023 $ 35 $ 37 Maintenance 2022 38 36 Money pool borrowings (advances) (Interest Charges)/Other Income, Net 2023 $ (b) $ (b) 2022 (b) (b) (a) Not applicable. (b) Amount less than $1 million.

Commitments And Contingencies

Commitments And Contingencies	3 Months Ended
	Mar. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
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 9 – Callaway Energy Center, Note 13 – Related-party Transactions, and Note 14 – 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. Environmental Matters Our electric generation, transmission, and distribution and natural gas distribution and storage operations must comply with a variety of statutes and regulations relating to the protection of the environment and human health and safety including permitting programs implemented by federal, state, and local authorities. Such environmental laws address air emissions; discharges to water bodies; the storage, handling and disposal of hazardous substances and waste materials; siting and land use requirements; and potential ecological impacts. 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. We employ dedicated personnel knowledgeable in environmental matters to oversee our business activities’ compliance with regulatory requirements of environmental laws. Environmental regulations have a significant impact on the electric utility industry and compliance with these regulations could be costly for Ameren Missouri, which operates coal-fired power plants. Regulations under the Clean Air Act that apply to the electric utility industry include the NSPS, the CSAPR, the MATS, and the National Ambient Air Quality Standards, which are subject to periodic review for certain pollutants. Collectively, these regulations cover a variety of pollutants, such as SO 2 , particulate matter, NO x , mercury, toxic metals and acid gases, and CO 2 emissions. Regulations implementing the Clean Water Act govern both intake and discharges of water, as well as evaluation of the ecological and biological impact of our operations and could require modifications to water intake structures or more stringent limitations on wastewater discharges. Depending upon the scope of modifications ultimately required by state regulators, capital expenditures associated with these modifications could be significant. The management and disposal of coal ash is regulated under the Resource Conservation and Recovery Act and the CCR Rule, which require the closure of surface impoundments at Ameren Missouri’s coal-fired energy centers. The individual or combined effects of compliance with existing and new environmental regulations could result in significant capital expenditures, increased operating costs, or the closure or alteration of operations at some of Ameren Missouri’s energy centers. 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. Additionally, Ameren Missouri’s wind generation facilities may be subject to operating restrictions to limit the impact on protected species. From April through October, in both 2021 and 2022, Ameren Missouri's High Prairie Renewable Energy Center curtailed nighttime operations to limit impacts on protected species. Seasonal nighttime curtailment began again in April 2023 as the critical biological season resumed, but the extent and duration of the curtailment is unknown at this time as assessment of mitigation technologies is ongoing. Ameren Missouri does not anticipate these operating curtailments to have a material impact on its results of operations, financial position, or liquidity. Ameren and Ameren Missouri estimate that they will need to make capital expenditures of $90 million to $120 million from 2023 through 2027 in order to comply with existing environmental regulations. Additional environmental controls beyond 2027 could be required. This estimate of capital expenditures includes surface impoundment closure and corrective action measures required by the CCR Rule and potential modifications to cooling water intake structures at existing power plants under Clean Water Act rules, all of which are discussed below. In addition to planned retirements of coal-fired energy centers as set forth in the 2022 Change to the 2020 IRP filed with the MoPSC in June 2022 and as noted in the NSR and Clean Air Act litigation and Illinois emissions standards discussed below, Ameren Missouri’s current plan for compliance with existing air emission regulations includes burning low-sulfur coal and installing new or optimizing existing air pollution control equipment. The actual amount of capital expenditures required to comply with existing environmental regulations may vary substantially from the above estimates because of uncertainty as to future permitting requirements by state regulators and the EPA, revisions to regulatory obligations, and varying cost of potential compliance strategies, 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 periodically amends and revises its regulations and proposes amendments to regulations and guidelines, which could ultimately result in the revision of all or part of such rules. Clean Air Act Federal and state laws, including the CSAPR, regulate emissions of SO 2 and NO x through the reduction of emissions at their source and the use and retirement of emission allowances. The CSAPR is implemented through a series of phases, and the second phase became effective in 2017. In April 2022, the EPA proposed plans for additional NO x emission reductions from power plants in Missouri, Illinois, and other states through revisions to the CSAPR. In January 2023, the EPA issued its final disapproval of Missouri’s proposed state implementation plan for addressing the transport of ozone under the Good Neighbor Plan of the Clean Air Act. The disapproval of the state plan allows the EPA to implement revisions to the CSAPR through a federal implementation plan. In March 2023, the EPA announced federal implementation plan requirements for Missouri, Illinois, and other states under the Good Neighbor Plan of the Clean Air Act. In April 2023, the Missouri Attorney General and Ameren Missouri separately filed lawsuits in the Eighth Circuit Court of Appeals challenging the EPA’s disapproval of the Missouri state plan. Unless stayed by a judicial action, in mid-2023, the EPA is expected to finalize a federal implementation plan reducing the amount of NO x allowances available for state budgets and imposing NO x emission limits on electric generating units. Ameren Missouri has complied with the current CSAPR requirements by minimizing emissions through the use of low-sulfur coal, operation of two scrubbers at its Sioux Energy Center, and optimization of other existing NO x air pollution control equipment. Restrictions on state budget NO x allowances could result in additional controls on Ameren Missouri’s generating units and/or the reduction of operations. Ameren Missouri is evaluating potential options to comply with the federal implementation plan. Any additional costs for compliance are expected to be recovered from customers, subject to MoPSC prudence review, through the FAC or higher base rates. CO 2 Emissions Standards In June 2022, the United States Supreme Court issued its decision in West Virginia v. EPA , clarifying that there are limits on how the EPA may regulate greenhouse gases absent further direction from the United States Congress. The court concluded that emission caps designed to shift generation from fossil-fuel-fired power plants to renewable energy facilities would require specific congressional authorization and that such authorization had not been given under the Clean Air Act. The decision by the United States Supreme Court may affect the EPA’s development of any new regulations to address CO 2 emissions from coal- and natural gas-fired power plants; however, at this time, Ameren Missouri cannot predict the impact of any such regulations or the decision by the United States Supreme Court on the results of operations, financial position, and liquidity of Ameren or Ameren Missouri. NSR and Clean Air Act Litigation In January 2011, the United States 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 alleging that projects performed in 2007 and 2010 at the coal-fired Rush Island Energy Center violated provisions of the Clean Air Act and Missouri law. In January 2017, the district court issued a liability ruling against Ameren Missouri and, in September 2019, entered a remedy order that required Ameren Missouri to install a flue gas desulfurization system at the Rush Island Energy Center and a dry sorbent injection system at the Labadie Energy Center. Following an appeal from Ameren Missouri in August 2021, the United States Court of Appeals for the Eighth Circuit affirmed the liability ruling and the district court’s remedy order as it related to the installation of a flue gas desulfurization system at the Rush Island Energy Center, but reversed the order as it related to the installation of a dry sorbent injection system at the Labadie Energy Center. In November 2021, the court of appeals issued an order denying requests for re-consideration sought by both Ameren Missouri and the United States Department of Justice. Based on its assessment of available legal, operational, and regulatory alternatives, Ameren Missouri filed a motion in December 2021, with the district court to modify the remedy order to allow the retirement of the Rush Island Energy Center in advance of its previously expected useful life in lieu of installing a flue gas desulfurization system. The March 31, 2024 compliance date contained in the district court’s September 2019 remedy order remains in effect unless extended by the district court. In 2022, in response to an Ameren Missouri request for a final, binding reliability assessment, the MISO designated the Rush Island Energy Center as a system support resource and concluded that certain mitigation measures, including transmission upgrades, should occur before the energy center is retired. The transmission upgrade projects have been approved by the MISO, and design and procurement activities necessary to complete the upgrades are underway. Ameren Missouri expects to complete the upgrades by mid-2025. In 2022, the FERC approved a system support resource agreement, which became effective as of September 1, 2022. The agreement details the manner of continued operation for a system support resource that results in operating during peak demand times and emergencies. The system support resource designation and the related agreement are subject to annual renewal and revision. In September 2022, the Rush Island Energy Center began operating consistent with the system support resource agreement. In addition, in October 2022, the FERC established hearing and settlement procedures in response to an August 2022 request from Ameren Missouri for recovery of non-energy costs under the related MISO tariff. The FERC is under no deadline to issue an order related to this proceeding. Revenues and costs under the MISO tariff are included in the FAC. The district court has the authority to determine the retirement date and operating parameters for the Rush Island Energy Center and is not bound by the MISO determination of the Rush Island Energy Center as a system support resource or the FERC’s approval. The district court is under no deadline to issue a ruling modifying the remedy order. Related to this matter, in February 2022, the MoPSC issued an order directing the MoPSC staff to review the planned accelerated retirement of the Rush Island Energy Center. See Note 2 – Rate and Regulatory Matters for additional information. In connection with the planned accelerated retirement of the Rush Island Energy Center, Ameren Missouri expects to seek approval from the MoPSC to finance the costs associated with the retirement, including the remaining unrecovered net plant balance associated with the facility, through the issuance of securitized utility tariff bonds pursuant to Missouri’s securitization statute. As of March 31, 2023, the Rush Island Energy Center had a net plant balance of approximately $0.6 billion included in plant to be abandoned, net, within “Property, Plant, and Equipment, Net” and a rate base of approximately $0.4 billion. See Note 1 – Summary of Significant Accounting Policies under Part II, Item 8, of the Form 10-K for additional information regarding plant to be abandoned, net. Ameren Missouri is unable to predict the ultimate resolution of this matter; however, such resolution could have a material adverse effect on the results of operations, financial position, and liquidity of Ameren and Ameren Missouri. Clean Water Act The EPA’s regulations implementing Section 316(b) of the Clean Water Act require power plant operators to evaluate cooling water intake structures and identify measures for reducing the number of aquatic organisms impinged on a power plant’s cooling water 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. Requirements of the rule are implemented by state regulators through the permit renewal process of each power plant’s water discharge permit. Permits for Ameren Missouri’s coal-fired and nuclear energy centers have been issued or are in the process of renewal. 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, prohibit effluent discharges of certain waste streams, and impose more stringent limitations on certain water discharges from power plants by 2025. To comply with these guidelines, Ameren Missouri installed dry ash handling systems and wastewater treatment facilities at its coal-fired energy centers. CCR Management The EPA’s CCR Rule establishes requirements for the management and disposal of CCR from coal-fired power plants and has resulted in the closure of surface impoundments at Ameren Missouri’s energy centers. Ameren Missouri plans to substantially complete the closures of the remaining surface impoundments at its Sioux Energy Center and retired Meramec Energy Center as required by the CCR Rule by the end of 2024. Ameren Missouri’s CCR management compliance plan includes installation of groundwater monitoring equipment and groundwater treatment facilities. Ameren and Ameren Missouri have AROs of $48 million recorded on their respective balance sheets as of March 31, 2023, associated with CCR storage facilities. 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. As of March 31, 2023, Ameren Illinois has remediated the majority of the 44 former MGP sites in Illinois and could substantially conclude remediation efforts at the remaining sites in 2023. The ICC allows Ameren Illinois to recover such remediation and related litigation costs from its electric and natural gas utility customers through environmental cost riders that are subject to annual prudence reviews by the ICC. As of March 31, 2023, Ameren Illinois estimated the remaining obligation related to these former MGP sites at $58 million to $108 million. Ameren and Ameren Illinois recorded a liability of $58 million to represent the estimated minimum obligation for these sites, as no other amount within the range was a better estimate. About half of the remaining liability recorded relates to remediation activities that are expected to be completed after 2023. 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 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. 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 historical practices will result in future environmental commitments, including additional or more stringent cleanup standards, or will affect our results of operations, financial position, or liquidity.

Callaway Energy Center

Callaway Energy Center	3 Months Ended
	Mar. 31, 2023
Nuclear Waste Matters [Abstract]
CALLAWAY ENERGY CENTER	CALLAWAY ENERGY CENTERSee Note 9 – Callaway Energy Center under Part II, Item 8, of the Form 10-K for information regarding spent nuclear fuel recovery, recovery of decommissioning costs, and the nuclear decommissioning trust fund. 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. 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 November 2020 and reflected within the ARO. In February 2021, the MoPSC approved no change in electric rates for decommissioning costs based on Ameren Missouri’s updated cost study funding analysis. See Note 13 – Supplemental Information for more information on Ameren Missouri’s AROs. Insurance The following table presents insurance coverage at Ameren Missouri’s Callaway Energy Center at April 1, 2023: Type and Source of Coverage Most Recent Maximum Coverages Maximum Assessments Public liability and nuclear worker liability: American Nuclear Insurers January 1, 2023 $ 450 $ — Pool participation (a) 13,210 (a) 138 (b) $ 13,660 (c) $ 138 Property damage: NEIL and EMANI April 1, 2023 $ 3,200 (d) $ 28 (e) Accidental outage: NEIL April 1, 2023 $ 490 (f) $ 9 (e) (a) Provided through mandatory participation in an industrywide retrospective premium assessment program. The maximum coverage available is dependent on the number of United States commercial reactors participating in the 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 $21 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 power 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) Accidental outage insurance provides for lost sales in the event of a prolonged accidental outage. Weekly indemnity up to $4.5 million for 52 weeks, which commences after the first 12 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 November 2018. 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 insured by NEIL are subject to industrywide aggregates, such that terrorist acts against one or more commercial nuclear power plants within a stated time period would be treated as a single event, and the owners of the nuclear power plants would share the 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, resulting from terrorist attacks. The EMANI policies are not subject to industrywide aggregates in the event of terrorist attacks on nuclear facilities. If losses from a nuclear incident at the Callaway Energy Center exceed insurance limits, 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	3 Months Ended
	Mar. 31, 2023
Retirement Benefits [Abstract]
RETIREMENT BENEFITS	RETIREMENT BENEFITS The following table presents the components of the net periodic benefit cost (income) incurred for Ameren’s pension and postretirement benefit plans for the three months ended March 31, 2023 and 2022: Pension Benefits Postretirement Benefits Three Months Three Months 2023 2022 2023 2022 Service cost (a) $ 23 $ 33 $ 3 $ 5 Non-service cost components: Interest cost 55 40 11 8 Expected return on plan assets (b) (83) (80) (23) (21) Amortization of (b) : Prior service benefit — — (1) (1) Actuarial loss (gain) (29) 6 (11) (4) Total non-service cost components (c) $ (57) $ (34) $ (24) $ (18) Net periodic benefit income (d) $ (34) $ (1) $ (21) $ (13) (a) Service cost, net of capitalization, is reflected in “Operating Expenses – Other operations and maintenance” on Ameren’s statement of income. (b) Prior service benefit is amortized on a straight-line basis over the average future service of active participants benefiting under a plan amendment. Net actuarial gains or losses related to the net benefit obligation subject to amortization are amortized on a straight-line basis over 10 years. The difference between the actual and expected return on plan assets is amortized over 4 years. (c) Non-service cost components are reflected in “Other Income, Net” on Ameren’s consolidated statement of income. See Note 5 – Other Income, Net for additional information. (d) Does not include the impact of the tracker for the difference between the level of pension and postretirement benefit costs (income) incurred by Ameren Missouri under GAAP and the level of such costs included in rates. Ameren Missouri and Ameren Illinois are responsible for their respective share of Ameren’s pension and other postretirement costs. The following table presents the respective share of net periodic pension and other postretirement benefit costs (income) incurred for the three months ended March 31, 2023 and 2022: Pension Benefits Postretirement Benefits Three Months Three Months 2023 2022 2023 2022 Ameren Missouri (a) $ (18) $ (1) $ (8) $ (3) Ameren Illinois (14) 1 (13) (10) Other (2) (1) — — Ameren (a) $ (34) $ (1) $ (21) $ (13) (a) Does not include the impact of the tracker for the difference between the level of pension and postretirement benefit costs (income) incurred by Ameren Missouri under GAAP and the level of such costs included in rates.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2023
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXES The following table presents a reconciliation of the federal statutory corporate income tax rate to the effective income tax rate for the three months ended March 31, 2023 and 2022: Ameren Ameren Missouri Ameren Illinois 2023 2022 2023 2022 2023 2022 Three Months Federal statutory corporate income tax rate 21 % 21 % 21 % 21 % 21 % 21 % Increases (decreases) from: Amortization of deferred investment tax credit — — — (1) — — Amortization of excess deferred taxes (a) (8) (8) (16) (16) (2) (2) Renewable and other tax credits (b) (5) (5) (10) (11) — — State tax 6 5 4 3 7 7 Stock-based compensation (1) (1) — — — — Other permanent items (1) — (3) — (1) — Effective income tax rate 12 % 12 % (4) % (4) % 25 % 26 % (a) Reflects the amortization of amounts resulting from the revaluation of deferred income taxes subject to regulatory ratemaking, which are being refunded to customers. Deferred income taxes are revalued when federal or state income tax rates change, and the offset to the revaluation of deferred income taxes subject to regulatory ratemaking is recorded to a regulatory asset or liability. (b) The benefit of the credits associated with Missouri renewable energy standard compliance is refunded to customers through the RESRAM.

Supplemental Information

Supplemental Information	3 Months Ended
	Mar. 31, 2023
Supplemental Information [Abstract]
Supplemental Information	SUPPLEMENTAL INFORMATION Cash, Cash Equivalents, and Restricted Cash The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the balance sheets and the statements of cash flows at March 31, 2023, and December 31, 2022: March 31, 2023 December 31, 2022 Ameren Ameren Ameren Ameren Ameren Ameren “Cash and cash equivalents” $ 10 $ 3 $ — $ 10 $ — $ — Restricted cash included in “Other current assets” 13 5 6 13 5 6 Restricted cash included in “Other assets” 211 — 211 185 — 185 Restricted cash included in “Nuclear decommissioning trust fund” 3 3 — 8 8 — Total cash, cash equivalents, and restricted cash $ 237 $ 11 $ 217 $ 216 $ 13 $ 191 Restricted cash included in “Other current assets” primarily represents funds held by an irrevocable Voluntary Employee Beneficiary Association (VEBA) trust, which provides health care benefits for active employees. Restricted cash included in “Other assets” on Ameren’s and Ameren Illinois’ balance sheets primarily represents amounts collected under a cost recovery rider restricted for use in the procurement of renewable energy credits and amounts in a trust fund restricted for the use of funding certain asbestos-related claims. Accounts Receivable “Accounts receivable – trade” on Ameren’s and Ameren Illinois’ balance sheets include certain receivables purchased at a discount from alternative retail electric suppliers that elect to participate in the utility consolidated billing program. At March 31, 2023, and December 31, 2022, “Other current liabilities” on Ameren’s and Ameren Illinois’ balance sheets included payables for purchased receivables of $35 million and $31 million, respectively. The following table provides a reconciliation of the beginning and ending amount of the allowance for doubtful accounts for the three months ended March 31, 2023 and 2022: Three Months 2023 2022 Ameren: Beginning of period $ 31 $ 29 Bad debt expense 10 4 Net write-offs (7) (5) End of period $ 34 $ 28 Ameren Missouri: Beginning of period $ 13 $ 13 Bad debt expense 2 1 Net write-offs (3) (3) End of period $ 12 $ 11 Ameren Illinois: (a) Beginning of period $ 18 $ 16 Bad debt expense 8 3 Net write-offs (4) (2) End of period $ 22 $ 17 (a) Ameren Illinois has rate-adjustment mechanisms that allow it to recover the difference between its actual net bad debt write-offs under GAAP, including those associated with receivables purchased from alternative retail electric suppliers, and the amount of net bad debt write-offs included in its base rates. As of March 31, 2023, accounts receivable balances that were 30 days or greater past due or that were a part of a deferred payment arrangement represented 23%, 15%, and 28%, or $153 million, $33 million, and $120 million, of Ameren’s, Ameren Missouri’s, and Ameren Illinois’ customer trade receivables before allowance for doubtful accounts, respectively. In comparison, as of March 31, 2022, these percentages were 20%, 15%, and 23%, or $116 million, $31 million, and $85 million, for Ameren, Ameren Missouri, and Ameren Illinois, respectively. Supplemental Cash Flow Information The following table provides noncash financing and investing activity excluded from the statements of cash flows for the three months ended March 31, 2023 and 2022: March 31, 2023 March 31, 2022 Ameren Ameren Ameren Ameren Ameren Ameren Investing: Accrued capital expenditures $ 298 $ 153 $ 138 $ 345 $ 194 $ 147 Net realized and unrealized gain/(loss) – nuclear decommissioning trust fund 54 54 — (71) (71) — Return of investment in industrial development revenue bonds (a) 240 240 — — — — Financing: Issuance of common stock for stock-based compensation $ 37 $ — $ — $ 31 $ — $ — Issuance of common stock under the DRPlus 7 — — 8 — — Termination of a financing obligation (a) 240 240 — — — — (a) In January 2023, Ameren Missouri and Audrain County mutually agreed to terminate a financing obligation agreement related to the CT energy center in Audrain County, which was scheduled to expire in December 2023. No cash was exchanged in connection with the termination of the agreement as the $240 million principal amount of the financing obligation due from Ameren Missouri was equal to the amount of bond service payments due to Ameren Missouri. Asset Retirement Obligations The following table provides a reconciliation of the beginning and ending carrying amount of AROs for the three months ended March 31, 2023: Ameren Ameren Ameren Balance at December 31, 2022 $ 782 (a) $ 4 (b) $ 786 (a) Liabilities settled (2) — (2) Accretion 8 (c) — 8 (c) Balance at March 31, 2023 $ 788 (a) $ 4 (b) $ 792 (a) (a) Balance included $23 million in “Other current liabilities” on the balance sheet as of both March 31, 2023, and December 31, 2022. (b) Included in “Other deferred credits and liabilities” on the balance sheet. (c) Accretion expense attributable to Ameren Missouri was recorded as a decrease to regulatory liabilities. Stock-based Compensation In the first quarter of 2023, Ameren granted 265,422 performance share units with a grant date fair value of $24 million and 116,701 restricted share units with a grant date fair value of $10 million. Awards vest approximately 3 years after the grant date or on a pro-rata basis upon death or eligible retirement. The performance share units vest based on the achievement of certain specified market performance measures (227,494 performance share units) or clean energy transition targets (37,928 performance share units). The exact number of shares issued pursuant to a performance share unit varies from 0% to 200% of the target award, depending on actual company performance relative to the performance goals. For the three months ended March 31, 2023 and 2022, excess tax benefits associated with the settlement of stock-based compensation awards reduced income tax expense by $6 million and $5 million, respectively. Deferred Compensation At March 31, 2023, and December 31, 2022, the present value of benefits to be paid for deferred compensation obligations was $85 million and $87 million, respectively, which was primarily reflected in “Other deferred credits and liabilities” on Ameren’s consolidated balance sheet. Operating Revenues As of March 31, 2023 and 2022, our remaining performance obligations for contracts with a term greater than one year were immaterial. The Ameren Companies elected not to disclose the aggregate amount of the transaction price allocated to the performance obligations that are unsatisfied as of the end of the reporting period for contracts with an initial expected term of one year or less. See Note 14 – Segment Information for disaggregated revenue information. Excise Taxes Ameren Missouri and Ameren Illinois collect from their customers excise taxes, including municipal and state excise taxes and gross receipts taxes that are levied on the sale or distribution of natural gas and electricity. The following table presents the excise taxes recorded on a gross basis in “Operating Revenues – Electric,” “Operating Revenues – Natural gas” and “Operating Expenses – Taxes other than income taxes” on the statements of income for the three months ended March 31, 2023 and 2022: Three Months 2023 2022 Ameren Missouri $ 34 $ 34 Ameren Illinois 37 45 Ameren $ 71 $ 79 Earnings per Share The following table reconciles the basic weighted-average number of common shares outstanding to the diluted weighted-average number of common shares outstanding for the three months ended March 31, 2023 and 2022: Three Months 2023 2022 Weighted-average Common Shares Outstanding – Basic 262.2 257.9 Assumed settlement of performance share units and restricted stock units 0.9 1.1 Weighted-average Common Shares Outstanding – Diluted (a) 263.1 259.0 (a) There was an immaterial number of anti-dilutive performance share units excluded from the earnings per diluted share calculations for the three months ended March 31, 2023 and 2022. The outstanding forward sale agreements as of March 31, 2023, were anti-dilutive and excluded from the earnings per diluted share calculation as calculated using the treasury stock method.

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2023
Segment Reporting [Abstract]
SEGMENT INFORMATION	SEGMENT INFORMATION The following tables present revenues, net income attributable to common shareholders, and capital expenditures by segment at Ameren and Ameren Illinois for the three months ended March 31, 2023 and 2022. Ameren, Ameren Missouri, and Ameren Illinois management review segment capital expenditure information rather than any individual or total asset amount. For additional information about our segments, see Note 16 – Segment Information under Part II, Item 8, of the Form 10-K. Ameren Ameren Missouri Ameren Illinois Electric Distribution Ameren Illinois Natural Gas Ameren Transmission Other Intersegment Eliminations Ameren Three Months 2023: External revenues $ 913 $ 624 $ 391 $ 134 $ — $ — $ 2,062 Intersegment revenues 10 — — 29 — (39) — Net income attributable to Ameren common shareholders 28 61 87 71 (a) 17 — 264 Capital expenditures 481 170 51 213 3 13 931 Three Months 2022: External revenues $ 808 $ 464 $ 481 $ 126 $ — $ — $ 1,879 Intersegment revenues 10 1 — 20 — (31) — Net income attributable to Ameren common shareholders 50 49 80 58 (a) 15 — 252 Capital expenditures 414 138 49 172 2 (1) 774 (a) Ameren Transmission earnings reflect an allocation of financing costs from Ameren (parent). Ameren Illinois Ameren Illinois Electric Distribution Ameren Illinois Natural Gas Ameren Illinois Transmission Intersegment Eliminations Ameren Illinois Three Months 2023: External revenues $ 624 $ 391 $ 86 $ — $ 1,101 Intersegment revenues — — 28 (28) — Net income available to common shareholder 61 87 50 — 198 Capital expenditures 170 51 186 — 407 Three Months 2022: External revenues $ 465 $ 481 $ 78 $ — $ 1,024 Intersegment revenues — — 20 (20) — Net income available to common shareholder 49 80 40 — 169 Capital expenditures 138 49 155 — 342 The following tables present disaggregated revenues by segment at Ameren and Ameren Illinois for the three months ended March 31, 2023 and 2022. Economic factors affect the nature, timing, amount, and uncertainty of revenues and cash flows in a similar manner across customer classes. Revenues from alternative revenue programs have a similar distribution among customer classes as revenues from contracts with customers. Other revenues not associated with contracts with customers are presented in the Other customer classification, along with electric transmission, off-system sales, and capacity revenues. Ameren Ameren Missouri Ameren Illinois Electric Distribution Ameren Illinois Natural Gas Ameren Transmission Intersegment Eliminations Ameren Three Months 2023: Residential $ 324 $ 382 $ — $ — $ — $ 706 Commercial 247 200 — — — 447 Industrial 61 48 — — — 109 Other 209 (6) — 163 (38) 328 Total electric revenues $ 841 $ 624 $ — $ 163 $ (38) $ 1,590 Residential $ 52 $ — $ 296 $ — $ — $ 348 Commercial 23 — 77 — — 100 Industrial 2 — 7 — — 9 Other 5 — 11 — (1) 15 Total natural gas revenues $ 82 $ — $ 391 $ — $ (1) $ 472 Total revenues (a) $ 923 $ 624 $ 391 $ 163 $ (39) $ 2,062 Three Months 2022: Residential $ 332 $ 263 $ — $ — $ — $ 595 Commercial 240 158 — — — 398 Industrial 57 45 — — — 102 Other 109 (1) — 146 (31) 223 Total electric revenues $ 738 $ 465 $ — $ 146 $ (31) $ 1,318 Residential $ 51 $ — $ 369 $ — $ — $ 420 Commercial 22 — 97 — — 119 Industrial 2 — 17 — — 19 Other 5 — (2) — — 3 Total natural gas revenues $ 80 $ — $ 481 $ — $ — $ 561 Total revenues (a) $ 818 $ 465 $ 481 $ 146 $ (31) $ 1,879 (a) The following table presents increases/(decreases) in revenues from alternative revenue programs and other revenues not from contracts with customers for the three months ended March 31, 2023 and 2022: Ameren Missouri Ameren Illinois Electric Distribution Ameren Illinois Natural Gas Ameren Transmission Ameren Three Months 2023: Revenues from alternative revenue programs $ (2) $ 64 $ 28 $ 8 $ 98 Other revenues not from contracts with customers (6) (a) 2 1 — (3) (a) Three Months 2022: Revenues from alternative revenue programs $ (6) $ 55 $ (5) $ 1 $ 45 Other revenues not from contracts with customers — (a) 2 1 — 3 (a) (a) Includes net realized losses on derivative power contracts. Ameren Illinois Ameren Illinois Electric Distribution Ameren Illinois Natural Gas Ameren Illinois Transmission Intersegment Eliminations Ameren Illinois Three Months 2023: Residential $ 382 $ 296 $ — $ — $ 678 Commercial 200 77 — — 277 Industrial 48 7 — — 55 Other (6) 11 114 (28) 91 Total revenues (a) $ 624 $ 391 $ 114 $ (28) $ 1,101 Three Months 2022: Residential $ 263 $ 369 $ — $ — $ 632 Commercial 158 97 — — 255 Industrial 45 17 — — 62 Other (1) (2) 98 (20) 75 Total revenues (a) $ 465 $ 481 $ 98 $ (20) $ 1,024 (a) The following table presents increases/(decreases) in revenues from alternative revenue programs and other revenues not from contracts with customers for the Ameren Illinois segments for the three months ended March 31, 2023 and 2022: Ameren Illinois Electric Distribution Ameren Illinois Natural Gas Ameren Illinois Transmission Ameren Illinois Three Months 2023: Revenues from alternative revenue programs $ 64 $ 28 $ 7 $ 99 Other revenues not from contracts with customers 2 1 — 3 Three Months 2022: Revenues from alternative revenue programs $ 55 $ (5) $ 1 $ 51 Other revenues not from contracts with customers 2 1 — 3

Summary Of Significant Accoun_2

Summary Of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2023
Accounting Policies [Abstract]
Nature of Operations	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 are listed below. Ameren has other subsidiaries that conduct other activities, such as providing shared services. • 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 in the MISO.
Consolidation	Ameren’s and Ameren Missouri’s financial statements are prepared on a consolidated basis and therefore include the accounts of their majority-owned subsidiaries. All intercompany transactions have been eliminated. Ameren Missouri’s subsidiaries were created for the ownership of renewable generation projects. Ameren Illinois has no subsidiaries. All tabular dollar amounts are in millions, unless otherwise indicated. Our accounting policies conform to GAAP. Our financial statements reflect all adjustments (which include normal, recurring adjustments) that are necessary, in our opinion, for a fair presentation of our results. The preparation of financial statements in conformity with GAAP requires management to make certain estimates and assumptions. Such estimates and assumptions affect reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the dates of financial statements, and reported amounts of revenues and expenses during the reporting periods. Actual results could differ from those estimates. The results of operations for an interim period may not give a true indication of results that may be expected for a full year. These financial statements should be read in conjunction with the financial statements and accompanying notes included in the Form 10-K.
Consolidation, Variable Interest Entity, Policy	Variable Interest Entities As of March 31, 2023, and December 31, 2022, Ameren had unconsolidated variable interests as a limited partner in various equity method investments, primarily to advance clean and resilient energy technologies, totaling $72 million and $68 million, respectively, included in “Other assets” on Ameren’s consolidated balance sheet. Any earnings or losses related to these investments are included in “Other Income, Net” on Ameren’s consolidated statement of income and comprehensive income. Ameren is not the primary beneficiary of these investments because it does not have the power to direct matters that most significantly affect the activities of these variable interest entities. As of March 31, 2023, the maximum exposure to loss related to these variable interests is limited to the investment in these partnerships of $72 million plus associated outstanding funding commitments of $17 million.
Life Insurance, Corporate Or Bank Owned	COLIAmeren and Ameren Illinois have COLI, which is recorded at the net cash surrender value. The net cash surrender value is the amount that can be realized under the insurance policies at the balance sheet date.
Derivatives, Policy	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; • actual cash outlays for the purchase of these commodities that differ from anticipated cash outlays; and • actual off-system sales revenues that differ from anticipated revenues. 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. 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. 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. The following disclosures exclude NPNS contracts and other non-derivative commodity contracts that are accounted for under the accrual method of accounting. 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
Deferred Compensation	Deferred Compensation At March 31, 2023, and December 31, 2022, the present value of benefits to be paid for deferred compensation obligations was $85 million and $87 million, respectively, which was primarily reflected in “Other deferred credits and liabilities” on Ameren’s consolidated balance sheet.
Revenue from Contract with Customer	Operating Revenues As of March 31, 2023 and 2022, our remaining performance obligations for contracts with a term greater than one year were immaterial. The Ameren Companies elected not to disclose the aggregate amount of the transaction price allocated to the performance obligations that are unsatisfied as of the end of the reporting period for contracts with an initial expected term of one year or less. See Note 14 – Segment Information for disaggregated revenue information.
Excise Taxes	Excise TaxesAmeren Missouri and Ameren Illinois collect from their customers excise taxes, including municipal and state excise taxes and gross receipts taxes that are levied on the sale or distribution of natural gas and electricity.

Rate and Regulatory Matters (Ta

Rate and Regulatory Matters (Tables)	3 Months Ended
	Mar. 31, 2023
Regulated Operations [Abstract]
Schedule of Solar Projects	The following table provides information with respect to each build-transfer agreement: Boomtown Solar Project (a) Huck Finn Solar Project (b) Agreement date February 2022 June 2022 Developer Invenergy Renewables, LLC EDF Renewables, Inc. Facility size 150-MW 200-MW Location Southeastern Illinois Central Missouri Status of MoPSC CCN Approved April 2023 Approved February 2023 Status of FERC approval of acquisition Expect to request by mid-2023 Received March 2023 Expected completion date (c) As early as fourth quarter 2024 As early as fourth quarter 2024 (a) The Boomtown Solar Project is expected to support Ameren Missouri’s transition to renewable energy generation and serve customers under the Renewable Solutions Program discussed below. (b) The Huck Finn Solar Project represents approximately $0.35 billion of capital expenditures and is expected to support Ameren Missouri’s compliance with the state of Missouri’s requirement of achieving 15% of retail sales from renewable energy sources, of which 2% must be derived from solar energy sources. (c) The expected completion dates may be impacted by the timing of FERC approval for the Boomtown Solar Project and potential sourcing issues resulting from a United States Department of Commerce investigation of solar panel components imported from four Southeast Asian countries initiated in March 2022 and the detention of certain solar panel components sourced from China as a result of the Uyghur Forced Labor Prevention Act that became effective in June 2022.
Schedule of MYRP details	The following table includes the forecasted revenue requirement, the requested ROE, the requested capital structure common equity percentage, and the forecasted average annual rate base for 2024 through 2027, as reflected in Ameren Illinois’ MYRP: Year Forecasted Revenue Requirement (in millions) Requested ROE Requested Capital Structure Common Equity Percentage (a) Forecasted Average Annual Rate Base (in billions) 2024 $1,282 10.5% 53.99% $4.3 2025 $1,373 10.5% 53.97% $4.6 2026 $1,477 10.5% 54.02% $5.0 2027 $1,556 10.5% 54.03% $5.3 (a) A capital structure of up to and including 50% common equity is deemed prudent and reasonable by law. A higher equity ratio requires specific ICC approval.

Short-Term Debt and Liquidity (

Short-Term Debt and Liquidity (Tables)	3 Months Ended
	Mar. 31, 2023
Debt Disclosure [Abstract]
Schedule of Short-term Debt	The following table presents commercial paper outstanding, net of issuance discounts, as of March 31, 2023, and December 31, 2022. There were no borrowings outstanding under the Credit Agreements as of March 31, 2023, or December 31, 2022. March 31, 2023 December 31, 2022 Ameren (parent) $ 727 $ 477 Ameren Missouri 197 329 Ameren Illinois 324 264 Ameren consolidated $ 1,248 $ 1,070 The following table summarizes the activity and relevant interest rates for Ameren (parent)’s, Ameren Missouri’s, and Ameren Illinois’ commercial paper issuances and borrowings under the Credit Agreements in the aggregate for the three months ended March 31, 2023 and 2022: Ameren Ameren Ameren Ameren 2023 Average daily amount outstanding $ 506 $ 436 $ 233 $ 1,175 Weighted-average interest rate 4.89 % 4.86 % 4.89 % 4.88 % Peak amount outstanding during period (a) $ 728 $ 592 $ 325 $ 1,381 Peak interest rate 5.55 % 5.55 % 5.60 % 5.60 % 2022 Average daily amount outstanding $ 282 $ 408 $ 99 $ 789 Weighted-average interest rate 0.41 % 0.44 % 0.33 % 0.41 % Peak amount outstanding during period (a) $ 466 $ 539 $ 142 $ 1,101 Peak interest rate 1.05 % 1.06 % 1.15 % 1.15 % (a) The timing of peak outstanding commercial paper issuances and borrowings under the Credit Agreements varies by company. Therefore, the sum of individual company peak amounts may not equal the Ameren consolidated peak for the period.

Other Income, Net (Tables)

Other Income, Net (Tables)	3 Months Ended
	Mar. 31, 2023
Other Nonoperating Income (Expense) [Abstract]
Other Income And Expenses	The following table presents the components of “Other Income, Net” in the Ameren Companies’ statements of income for the three months ended March 31, 2023 and 2022: Three Months 2023 2022 Ameren: Allowance for equity funds used during construction $ 9 $ 8 Interest income on industrial development revenue bonds 1 6 Non-service cost components of net periodic benefit income (a) 64 46 Miscellaneous income 9 4 Earnings related to equity method investments 2 3 Donations (2) (2) Miscellaneous expense (5) (5) Total Other Income, Net $ 78 $ 60 Ameren Missouri: Allowance for equity funds used during construction $ 4 $ 4 Interest income on industrial development revenue bonds 1 6 Non-service cost components of net periodic benefit income (a) 14 14 Miscellaneous income 4 2 Donations (1) (1) Miscellaneous expense (3) (2) Total Other Income, Net $ 19 $ 23 Ameren Illinois: Allowance for equity funds used during construction $ 4 $ 4 Non-service cost components of net periodic benefit income 31 21 Miscellaneous income 5 2 Donations (1) (1) Miscellaneous expense (2) (2) Total Other Income, Net $ 37 $ 24 (a) For the three months ended March 31, 2023 and 2022, the non-service cost components of net periodic benefit income were adjusted by amounts deferred of $17 million and $6 million, respectively, due to a regulatory tracking mechanism for the difference between the level of such costs incurred by Ameren Missouri under GAAP and the level of such costs included in rates. See Note 11– Retirement Benefits for additional information.

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2023
Derivative Instruments and Hedging Activities Disclosure [Abstract]
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 March 31, 2023, and December 31, 2022. As of March 31, 2023, these contracts extended through October 2025, October 2029, May 2032 and March 2024 for fuel oils, natural gas, power and uranium, respectively. Quantity (in millions) March 31, 2023 December 31, 2022 Commodity Ameren Missouri Ameren Illinois Ameren Ameren Missouri Ameren Illinois Ameren Fuel oils (in gallons) 18 — 18 18 — 18 Natural gas (in mmbtu) 60 185 245 48 157 205 Power (in MWhs) 1 6 7 1 6 7 Uranium (pounds in thousands) 186 — 186 514 — 514
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 March 31, 2023, and December 31, 2022: March 31, 2023 December 31, 2022 Balance Sheet Location Ameren Ameren Ameren Ameren Ameren Ameren Fuel oils Other current assets $ 8 $ — $ 8 $ 13 $ — $ 13 Other assets 2 — 2 3 — 3 Natural gas Other current assets 1 5 6 7 23 30 Other assets 8 8 16 9 11 20 Power Other current assets 5 — 5 14 2 16 Other assets — 1 1 — 4 4 Uranium Other current assets 1 — 1 2 — 2 Other assets — — — 1 — 1 Total assets $ 25 $ 14 $ 39 $ 49 $ 40 $ 89 Fuel oils Other deferred credits and liabilities $ 1 $ — $ 1 $ — $ — $ — Natural gas Other current liabilities 9 33 42 7 20 27 Other deferred credits and liabilities 5 12 17 2 9 11 Power Other current liabilities 17 10 27 59 2 61 Other deferred credits and liabilities — 43 43 — 37 37 Total liabilities $ 32 $ 98 $ 130 $ 68 $ 68 $ 136
Offsetting Assets and Liabilities	Th e following table p rovides the recognized gross derivative balances and the net amounts of those derivatives subject to an enforceable master netting arrangement or similar agreement as of March 31, 2023, and December 31, 2022: Gross Amounts Not Offset in the Balance Sheet Commodity Contracts Eligible to be Offset Gross Amounts Recognized in the Balance Sheet Derivative Instruments Cash Collateral Received/Posted (a) Net March 31, 2023 Assets: Ameren Missouri $ 25 $ 9 $ — $ 16 Ameren Illinois 14 11 — 3 Ameren $ 39 $ 20 $ — $ 19 Liabilities: Ameren Missouri $ 32 $ 9 $ 16 $ 7 Ameren Illinois 98 11 — 87 Ameren $ 130 $ 20 $ 16 $ 94 December 31, 2022 Assets: Ameren Missouri $ 49 $ 9 $ — $ 40 Ameren Illinois 40 20 — 20 Ameren $ 89 $ 29 $ — $ 60 Liabilities: Ameren Missouri $ 68 $ 9 $ 56 $ 3 Ameren Illinois 68 20 — 48 Ameren $ 136 $ 29 $ 56 $ 51 (a) Cash collateral received reduces gross asset balances and is included in “Other current liabilities” and “Other deferred credits and liabilities” on the balance sheet. Cash collateral posted reduces gross liability balances and is included in “Current collateral assets” and “Other assets” on the balance sheet for Ameren and Ameren Missouri and “Other current assets” and “Other assets” for Ameren Illinois.
Derivative Instruments With Credit Risk-Related Contingent Features	The following table presents, as of March 31, 2023, 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: Aggregate Fair Value of Derivative Liabilities (a) Cash Potential Aggregate Amount of Additional Collateral Required (b) Ameren Missouri $ 16 $ — $ 7 Ameren Illinois 45 — 36 Ameren $ 61 $ — $ 43 (a) Before consideration of master netting arrangements or similar agreements. (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 Measurements (Tables)	3 Months Ended
	Mar. 31, 2023
Fair Value Disclosures [Abstract]
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 March 31, 2023, and December 31, 2022: March 31, 2023 December 31, 2022 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets: Ameren Missouri Derivative assets – commodity contracts: Fuel oils $ 10 $ — $ — $ 10 $ 16 $ — $ — $ 16 Natural gas — 9 — 9 1 15 — 16 Power — — 5 5 — — 14 14 Uranium — — 1 1 — — 3 3 Total derivative assets – commodity contracts $ 10 $ 9 $ 6 $ 25 $ 17 $ 15 $ 17 $ 49 Nuclear decommissioning trust fund: Equity securities: U.S. large capitalization $ 668 $ — $ — $ 668 $ 618 $ — $ — $ 618 Debt securities: U.S. Treasury and agency securities — 149 — 149 — 137 — 137 Corporate bonds — 123 — 123 — 122 — 122 Other — 74 — 74 — 70 — 70 Total nuclear decommissioning trust fund $ 668 $ 346 $ — $ 1,014 (a) $ 618 $ 329 $ — $ 947 (a) Total Ameren Missouri $ 678 $ 355 $ 6 $ 1,039 $ 635 $ 344 $ 17 $ 996 Ameren Illinois Derivative assets – commodity contracts: Natural gas $ — $ 10 $ 3 $ 13 $ 1 $ 28 $ 5 $ 34 Power — — 1 1 — — 6 6 Total Ameren Illinois $ — $ 10 $ 4 $ 14 $ 1 $ 28 $ 11 $ 40 Ameren Derivative assets – commodity contracts (b) $ 10 $ 19 $ 10 $ 39 $ 18 $ 43 $ 28 $ 89 Nuclear decommissioning trust fund (c) 668 346 — 1,014 (a) 618 329 — 947 (a) Total Ameren $ 678 $ 365 $ 10 $ 1,053 $ 636 $ 372 $ 28 $ 1,036 Liabilities: Ameren Missouri Derivative liabilities – commodity contracts: Fuel oils $ 1 $ — $ — $ 1 $ — $ — $ — $ — Natural gas — 11 3 14 — 6 3 9 Power 17 — — 17 57 — 2 59 Total Ameren Missouri $ 18 $ 11 $ 3 $ 32 $ 57 $ 6 $ 5 $ 68 Ameren Illinois Derivative liabilities – commodity contracts: Natural gas $ 1 $ 36 $ 8 $ 45 $ — $ 19 $ 10 $ 29 Power — — 53 53 — — 39 39 Total Ameren Illinois $ 1 $ 36 $ 61 $ 98 $ — $ 19 $ 49 $ 68 Ameren Derivative liabilities – commodity contracts (b) $ 19 $ 47 $ 64 $ 130 $ 57 $ 25 $ 54 $ 136 (a) Balance excludes $5 million and $11 million of cash and cash equivalents, receivables, payables, and accrued income, net, for March 31, 2023, and December 31, 2022, respectively. (b) See the Ameren Missouri and Ameren Illinois sections of the table for a breakout of the fair value of Ameren’s derivative assets and liabilities by type of commodity. (c) See the Ameren Missouri section of the table for a breakout of the fair value of Ameren’s nuclear decommissioning trust fund by investment type.
Schedule Of Changes In The Fair Value Of Financial Assets And Liabilities Classified As Level Three In The Fair Value Hierarchy	The following table presents the fair value reconciliation of Level 3 power derivative contract assets and liabilities measured at fair value on a recurring basis for the three months ended March 31, 2023 and 2022: 2023 2022 Ameren Missouri Ameren Illinois Ameren Ameren Missouri Ameren Illinois Ameren For the three months ended March 31: Beginning balance at January 1 $ 12 $ (33) $ (21) $ (15) $ (117) $ (132) Realized and unrealized gains/(losses) included in regulatory assets/liabilities (6) (20) (26) (41) 42 1 Settlements (1) 1 — 3 1 4 Ending balance at March 31 $ 5 $ (52) $ (47) $ (53) $ (74) $ (127) Change in unrealized gains/(losses) related to assets/liabilities held at March 31 $ (2) $ (18) $ (20) $ (38) $ 42 $ 4
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis, Valuation Techniques	The following table describes the valuation techniques and significant unobservable inputs utilized for the fair value of our Level 3 power derivative contract assets and liabilities as of March 31, 2023, and December 31, 2022: Fair Value Weighted Average (b) Commodity Assets Liabilities Valuation Technique(s) Unobservable Input (a) Range 2023 Power (c) $ 6 $ (53) Discounted cash flow Average forward peak and off-peak pricing – forwards/swaps ($/MWh) 22 – 74 46 Nodal basis ($/MWh) (9) – (1) (4) 2022 Power (d) $ 20 $ (41) Discounted cash flow Average forward peak and off-peak pricing – forwards/swaps ($/MWh) 38 – 89 51 Nodal basis ($/MWh) (10) – (1) (4) Trend rate (%) 0 1 0 (a) Generally, significant increases (decreases) in these inputs in isolation would result in a significantly higher (lower) fair value measurement. (b) Unobservable inputs were weighted by relative fair value. (c) Valuations use visible forward prices adjusted for nodal-to-hub basis differentials. (d) Valuations through 2031 use visible forward prices adjusted for nodal-to-hub basis differentials. Valuations beyond 2031 use a trend rate factor and are similarly adjusted for nodal-to-hub basis differentials.
Schedule of Financial Assets and Liabilities	The following table sets forth the carrying amount and, by level within the fair value hierarchy, the fair value of financial assets and liabilities disclosed, but not recorded, at fair value as of March 31, 2023, and December 31, 2022: Carrying Fair Value Level 1 Level 2 Level 3 Total March 31, 2023 Ameren: Cash, cash equivalents, and restricted cash $ 237 $ 237 $ — $ — $ 237 Short-term debt 1,248 — 1,248 — 1,248 Long-term debt (including current portion) 14,281 (a) — 12,408 473 (b) 12,881 Ameren Missouri: Cash, cash equivalents, and restricted cash $ 11 $ 11 $ — $ — $ 11 Short-term debt 197 — 197 — 197 Long-term debt (including current portion) 6,341 (a) — 5,706 — 5,706 Ameren Illinois: Cash, cash equivalents, and restricted cash $ 217 $ 217 $ — $ — $ 217 Short-term debt 324 — 324 — 324 Long-term debt (including current portion) 4,836 (a) — 4,368 — 4,368 December 31, 2022 Ameren: Cash, cash equivalents, and restricted cash $ 216 $ 216 $ — $ — $ 216 Investment in industrial development revenue bonds (c) 240 — 240 — 240 Short-term debt 1,070 — 1,070 — 1,070 Long-term debt (including current portion) (c) 14,025 (a) — 11,989 464 (b) 12,453 Ameren Missouri: Cash, cash equivalents, and restricted cash $ 13 $ 13 $ — $ — $ 13 Investment in industrial development revenue bonds (c) 240 — 240 — 240 Short-term debt 329 — 329 — 329 Long-term debt (including current portion) (c) 6,086 (a) — 5,365 — 5,365 Ameren Illinois: Cash, cash equivalents, and restricted cash $ 191 $ 191 $ — $ — $ 191 Short-term debt 264 — 264 — 264 Long-term debt (including current portion) 4,835 (a) — 4,320 — 4,320 (a) Included unamortized debt issuance costs, which were excluded from the fair value measurement, of $103 million, $45 million, and $44 million for Ameren, Ameren Missouri, and Ameren Illinois, respectively, as of March 31, 2023. Included unamortized debt issuance costs, which were excluded from the fair value measurement, of $99 million, $41 million, and $44 million for Ameren, Ameren Missouri, and Ameren Illinois, respectively, as of December 31, 2022. (b) The Level 3 fair value amount consists of ATXI’s senior unsecured notes. (c) Ameren and Ameren Missouri had an investment in industrial development revenue bonds, classified as held-to-maturity and recorded in “Other Assets,” that were equal to the finance obligation for the Audrain CT energy center. As of December 31, 2022, the carrying amount of the investment in industrial development revenue bonds and the finance obligation approximated fair value.

Related Party Transactions (Tab

Related Party Transactions (Tables)	3 Months Ended
	Mar. 31, 2023
Related Party Transactions [Abstract]
Schedule of Affiliate Receivables and Payables	The following table presents the affiliate balances related to income taxes for Ameren Missouri and Ameren Illinois as of March 31, 2023, and December 31, 2022: March 31, 2023 December 31, 2022 Ameren Missouri Ameren Illinois Ameren Missouri Ameren Illinois Income taxes payable to parent (a) $ — $ 80 $ — $ 50 Income taxes receivable from parent (b) 54 — 39 — (a) Included in “Accounts payable – affiliates” on the balance sheet. (b) Included in “Accounts receivable – affiliates” on the balance sheet.
Schedule of Related Party Transactions	The following table presents the impact on Ameren Missouri and Ameren Illinois of related-party transactions for the three months ended March 31, 2023 and 2022: Three Months Agreement Income Statement Ameren Ameren Ameren Missouri power supply Operating Revenues 2023 $ (b) $ (a) agreements with Ameren Illinois 2022 4 (a) Ameren Missouri and Ameren Illinois Operating Revenues 2023 $ 10 $ (b) rent and facility services 2022 6 (b) Ameren Missouri and Ameren Illinois miscellaneous Operating Revenues 2023 $ (b) $ (b) support services 2022 (b) 1 Total Operating Revenues 2023 $ 10 $ (b) 2022 10 1 Ameren Illinois power supply Purchased Power 2023 $ (a) $ (b) agreements with Ameren Missouri 2022 (a) 4 Ameren Missouri and Ameren Illinois Purchased Power 2023 $ (b) $ (b) transmission services from ATXI 2022 (b) (b) Total Purchased Power 2023 $ (b) $ (b) 2022 (b) 4 Ameren Missouri and Ameren Illinois Other Operations and Maintenance 2023 $ (b) $ 2 rent and facility services 2022 (b) 1 Ameren Services support services Other Operations and Maintenance 2023 $ 35 $ 35 agreement 2022 38 35 Total Other Operations and 2023 $ 35 $ 37 Maintenance 2022 38 36 Money pool borrowings (advances) (Interest Charges)/Other Income, Net 2023 $ (b) $ (b) 2022 (b) (b) (a) Not applicable. (b) Amount less than $1 million.

Callaway Energy Center (Tables)

Callaway Energy Center (Tables)	3 Months Ended
	Mar. 31, 2023
Nuclear Waste Matters [Abstract]
Schedule of Insurance Coverage at Callaway Energy Center	The following table presents insurance coverage at Ameren Missouri’s Callaway Energy Center at April 1, 2023: Type and Source of Coverage Most Recent Maximum Coverages Maximum Assessments Public liability and nuclear worker liability: American Nuclear Insurers January 1, 2023 $ 450 $ — Pool participation (a) 13,210 (a) 138 (b) $ 13,660 (c) $ 138 Property damage: NEIL and EMANI April 1, 2023 $ 3,200 (d) $ 28 (e) Accidental outage: NEIL April 1, 2023 $ 490 (f) $ 9 (e) (a) Provided through mandatory participation in an industrywide retrospective premium assessment program. The maximum coverage available is dependent on the number of United States commercial reactors participating in the 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 $21 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 power 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) Accidental outage insurance provides for lost sales in the event of a prolonged accidental outage. Weekly indemnity up to $4.5 million for 52 weeks, which commences after the first 12 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)

Retirement Benefits (Tables)	3 Months Ended
	Mar. 31, 2023
Retirement Benefits [Abstract]
Components Of Net Periodic Benefit Cost	The following table presents the components of the net periodic benefit cost (income) incurred for Ameren’s pension and postretirement benefit plans for the three months ended March 31, 2023 and 2022: Pension Benefits Postretirement Benefits Three Months Three Months 2023 2022 2023 2022 Service cost (a) $ 23 $ 33 $ 3 $ 5 Non-service cost components: Interest cost 55 40 11 8 Expected return on plan assets (b) (83) (80) (23) (21) Amortization of (b) : Prior service benefit — — (1) (1) Actuarial loss (gain) (29) 6 (11) (4) Total non-service cost components (c) $ (57) $ (34) $ (24) $ (18) Net periodic benefit income (d) $ (34) $ (1) $ (21) $ (13) (a) Service cost, net of capitalization, is reflected in “Operating Expenses – Other operations and maintenance” on Ameren’s statement of income. (b) Prior service benefit is amortized on a straight-line basis over the average future service of active participants benefiting under a plan amendment. Net actuarial gains or losses related to the net benefit obligation subject to amortization are amortized on a straight-line basis over 10 years. The difference between the actual and expected return on plan assets is amortized over 4 years. (c) Non-service cost components are reflected in “Other Income, Net” on Ameren’s consolidated statement of income. See Note 5 – Other Income, Net for additional information. (d) Does not include the impact of the tracker for the difference between the level of pension and postretirement benefit costs (income) incurred by Ameren Missouri under GAAP and the level of such costs included in rates.
Summary Of Benefit Plan Costs Incurred	Ameren Missouri and Ameren Illinois are responsible for their respective share of Ameren’s pension and other postretirement costs. The following table presents the respective share of net periodic pension and other postretirement benefit costs (income) incurred for the three months ended March 31, 2023 and 2022: Pension Benefits Postretirement Benefits Three Months Three Months 2023 2022 2023 2022 Ameren Missouri (a) $ (18) $ (1) $ (8) $ (3) Ameren Illinois (14) 1 (13) (10) Other (2) (1) — — Ameren (a) $ (34) $ (1) $ (21) $ (13) (a) Does not include the impact of the tracker for the difference between the level of pension and postretirement benefit costs (income) incurred by Ameren Missouri under GAAP and the level of such costs included in rates.

Income Taxes Income Taxes (Tabl

Income Taxes Income Taxes (Tables)	3 Months Ended
	Mar. 31, 2023
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation	The following table presents a reconciliation of the federal statutory corporate income tax rate to the effective income tax rate for the three months ended March 31, 2023 and 2022: Ameren Ameren Missouri Ameren Illinois 2023 2022 2023 2022 2023 2022 Three Months Federal statutory corporate income tax rate 21 % 21 % 21 % 21 % 21 % 21 % Increases (decreases) from: Amortization of deferred investment tax credit — — — (1) — — Amortization of excess deferred taxes (a) (8) (8) (16) (16) (2) (2) Renewable and other tax credits (b) (5) (5) (10) (11) — — State tax 6 5 4 3 7 7 Stock-based compensation (1) (1) — — — — Other permanent items (1) — (3) — (1) — Effective income tax rate 12 % 12 % (4) % (4) % 25 % 26 % (a) Reflects the amortization of amounts resulting from the revaluation of deferred income taxes subject to regulatory ratemaking, which are being refunded to customers. Deferred income taxes are revalued when federal or state income tax rates change, and the offset to the revaluation of deferred income taxes subject to regulatory ratemaking is recorded to a regulatory asset or liability. (b) The benefit of the credits associated with Missouri renewable energy standard compliance is refunded to customers through the RESRAM.

Supplemental Information (Table

Supplemental Information (Tables)	3 Months Ended
	Mar. 31, 2023
Supplemental Information [Abstract]
Schedule of Cash and Cash Equivalents Including Restricted Cash	The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the balance sheets and the statements of cash flows at March 31, 2023, and December 31, 2022: March 31, 2023 December 31, 2022 Ameren Ameren Ameren Ameren Ameren Ameren “Cash and cash equivalents” $ 10 $ 3 $ — $ 10 $ — $ — Restricted cash included in “Other current assets” 13 5 6 13 5 6 Restricted cash included in “Other assets” 211 — 211 185 — 185 Restricted cash included in “Nuclear decommissioning trust fund” 3 3 — 8 8 — Total cash, cash equivalents, and restricted cash $ 237 $ 11 $ 217 $ 216 $ 13 $ 191
Schedule of Accounts, Notes, Loans and Financing Receivable	The following table provides a reconciliation of the beginning and ending amount of the allowance for doubtful accounts for the three months ended March 31, 2023 and 2022: Three Months 2023 2022 Ameren: Beginning of period $ 31 $ 29 Bad debt expense 10 4 Net write-offs (7) (5) End of period $ 34 $ 28 Ameren Missouri: Beginning of period $ 13 $ 13 Bad debt expense 2 1 Net write-offs (3) (3) End of period $ 12 $ 11 Ameren Illinois: (a) Beginning of period $ 18 $ 16 Bad debt expense 8 3 Net write-offs (4) (2) End of period $ 22 $ 17 (a) Ameren Illinois has rate-adjustment mechanisms that allow it to recover the difference between its actual net bad debt write-offs under GAAP, including those associated with receivables purchased from alternative retail electric suppliers, and the amount of net bad debt write-offs included in its base rates.
Schedule of Cash Flow, Supplemental Disclosures	The following table provides noncash financing and investing activity excluded from the statements of cash flows for the three months ended March 31, 2023 and 2022: March 31, 2023 March 31, 2022 Ameren Ameren Ameren Ameren Ameren Ameren Investing: Accrued capital expenditures $ 298 $ 153 $ 138 $ 345 $ 194 $ 147 Net realized and unrealized gain/(loss) – nuclear decommissioning trust fund 54 54 — (71) (71) — Return of investment in industrial development revenue bonds (a) 240 240 — — — — Financing: Issuance of common stock for stock-based compensation $ 37 $ — $ — $ 31 $ — $ — Issuance of common stock under the DRPlus 7 — — 8 — — Termination of a financing obligation (a) 240 240 — — — — (a) In January 2023, Ameren Missouri and Audrain County mutually agreed to terminate a financing obligation agreement related to the CT energy center in Audrain County, which was scheduled to expire in December 2023. No cash was exchanged in connection with the termination of the agreement as the $240 million principal amount of the financing obligation due from Ameren Missouri was equal to the amount of bond service payments due to Ameren Missouri.
Asset Retirement Obligation Disclosure	The following table provides a reconciliation of the beginning and ending carrying amount of AROs for the three months ended March 31, 2023: Ameren Ameren Ameren Balance at December 31, 2022 $ 782 (a) $ 4 (b) $ 786 (a) Liabilities settled (2) — (2) Accretion 8 (c) — 8 (c) Balance at March 31, 2023 $ 788 (a) $ 4 (b) $ 792 (a) (a) Balance included $23 million in “Other current liabilities” on the balance sheet as of both March 31, 2023, and December 31, 2022. (b) Included in “Other deferred credits and liabilities” on the balance sheet. (c) Accretion expense attributable to Ameren Missouri was recorded as a decrease to regulatory liabilities.
Schedule of excise taxes	The following table presents the excise taxes recorded on a gross basis in “Operating Revenues – Electric,” “Operating Revenues – Natural gas” and “Operating Expenses – Taxes other than income taxes” on the statements of income for the three months ended March 31, 2023 and 2022: Three Months 2023 2022 Ameren Missouri $ 34 $ 34 Ameren Illinois 37 45 Ameren $ 71 $ 79
Schedule of Earnings Per Share, Basic and Diluted	The following table reconciles the basic weighted-average number of common shares outstanding to the diluted weighted-average number of common shares outstanding for the three months ended March 31, 2023 and 2022: Three Months 2023 2022 Weighted-average Common Shares Outstanding – Basic 262.2 257.9 Assumed settlement of performance share units and restricted stock units 0.9 1.1 Weighted-average Common Shares Outstanding – Diluted (a) 263.1 259.0 (a) There was an immaterial number of anti-dilutive performance share units excluded from the earnings per diluted share calculations for the three months ended March 31, 2023 and 2022. The outstanding forward sale agreements as of March 31, 2023, were anti-dilutive and excluded from the earnings per diluted share calculation as calculated using the treasury stock method.

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2023
Segment Reporting [Abstract]
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 months ended March 31, 2023 and 2022. Ameren, Ameren Missouri, and Ameren Illinois management review segment capital expenditure information rather than any individual or total asset amount. For additional information about our segments, see Note 16 – Segment Information under Part II, Item 8, of the Form 10-K. Ameren Ameren Missouri Ameren Illinois Electric Distribution Ameren Illinois Natural Gas Ameren Transmission Other Intersegment Eliminations Ameren Three Months 2023: External revenues $ 913 $ 624 $ 391 $ 134 $ — $ — $ 2,062 Intersegment revenues 10 — — 29 — (39) — Net income attributable to Ameren common shareholders 28 61 87 71 (a) 17 — 264 Capital expenditures 481 170 51 213 3 13 931 Three Months 2022: External revenues $ 808 $ 464 $ 481 $ 126 $ — $ — $ 1,879 Intersegment revenues 10 1 — 20 — (31) — Net income attributable to Ameren common shareholders 50 49 80 58 (a) 15 — 252 Capital expenditures 414 138 49 172 2 (1) 774 (a) Ameren Transmission earnings reflect an allocation of financing costs from Ameren (parent). Ameren Illinois Ameren Illinois Electric Distribution Ameren Illinois Natural Gas Ameren Illinois Transmission Intersegment Eliminations Ameren Illinois Three Months 2023: External revenues $ 624 $ 391 $ 86 $ — $ 1,101 Intersegment revenues — — 28 (28) — Net income available to common shareholder 61 87 50 — 198 Capital expenditures 170 51 186 — 407 Three Months 2022: External revenues $ 465 $ 481 $ 78 $ — $ 1,024 Intersegment revenues — — 20 (20) — Net income available to common shareholder 49 80 40 — 169 Capital expenditures 138 49 155 — 342
Disaggregation of Revenue	The following tables present disaggregated revenues by segment at Ameren and Ameren Illinois for the three months ended March 31, 2023 and 2022. Economic factors affect the nature, timing, amount, and uncertainty of revenues and cash flows in a similar manner across customer classes. Revenues from alternative revenue programs have a similar distribution among customer classes as revenues from contracts with customers. Other revenues not associated with contracts with customers are presented in the Other customer classification, along with electric transmission, off-system sales, and capacity revenues. Ameren Ameren Missouri Ameren Illinois Electric Distribution Ameren Illinois Natural Gas Ameren Transmission Intersegment Eliminations Ameren Three Months 2023: Residential $ 324 $ 382 $ — $ — $ — $ 706 Commercial 247 200 — — — 447 Industrial 61 48 — — — 109 Other 209 (6) — 163 (38) 328 Total electric revenues $ 841 $ 624 $ — $ 163 $ (38) $ 1,590 Residential $ 52 $ — $ 296 $ — $ — $ 348 Commercial 23 — 77 — — 100 Industrial 2 — 7 — — 9 Other 5 — 11 — (1) 15 Total natural gas revenues $ 82 $ — $ 391 $ — $ (1) $ 472 Total revenues (a) $ 923 $ 624 $ 391 $ 163 $ (39) $ 2,062 Three Months 2022: Residential $ 332 $ 263 $ — $ — $ — $ 595 Commercial 240 158 — — — 398 Industrial 57 45 — — — 102 Other 109 (1) — 146 (31) 223 Total electric revenues $ 738 $ 465 $ — $ 146 $ (31) $ 1,318 Residential $ 51 $ — $ 369 $ — $ — $ 420 Commercial 22 — 97 — — 119 Industrial 2 — 17 — — 19 Other 5 — (2) — — 3 Total natural gas revenues $ 80 $ — $ 481 $ — $ — $ 561 Total revenues (a) $ 818 $ 465 $ 481 $ 146 $ (31) $ 1,879 (a) The following table presents increases/(decreases) in revenues from alternative revenue programs and other revenues not from contracts with customers for the three months ended March 31, 2023 and 2022: Ameren Missouri Ameren Illinois Electric Distribution Ameren Illinois Natural Gas Ameren Transmission Ameren Three Months 2023: Revenues from alternative revenue programs $ (2) $ 64 $ 28 $ 8 $ 98 Other revenues not from contracts with customers (6) (a) 2 1 — (3) (a) Three Months 2022: Revenues from alternative revenue programs $ (6) $ 55 $ (5) $ 1 $ 45 Other revenues not from contracts with customers — (a) 2 1 — 3 (a) (a) Includes net realized losses on derivative power contracts. Ameren Illinois Ameren Illinois Electric Distribution Ameren Illinois Natural Gas Ameren Illinois Transmission Intersegment Eliminations Ameren Illinois Three Months 2023: Residential $ 382 $ 296 $ — $ — $ 678 Commercial 200 77 — — 277 Industrial 48 7 — — 55 Other (6) 11 114 (28) 91 Total revenues (a) $ 624 $ 391 $ 114 $ (28) $ 1,101 Three Months 2022: Residential $ 263 $ 369 $ — $ — $ 632 Commercial 158 97 — — 255 Industrial 45 17 — — 62 Other (1) (2) 98 (20) 75 Total revenues (a) $ 465 $ 481 $ 98 $ (20) $ 1,024 (a) The following table presents increases/(decreases) in revenues from alternative revenue programs and other revenues not from contracts with customers for the Ameren Illinois segments for the three months ended March 31, 2023 and 2022: Ameren Illinois Electric Distribution Ameren Illinois Natural Gas Ameren Illinois Transmission Ameren Illinois Three Months 2023: Revenues from alternative revenue programs $ 64 $ 28 $ 7 $ 99 Other revenues not from contracts with customers 2 1 — 3 Three Months 2022: Revenues from alternative revenue programs $ 55 $ (5) $ 1 $ 51 Other revenues not from contracts with customers 2 1 — 3

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Basis Of Presentation And Significant Accounting Policies [Line Items]
Unconsolidated variable interest	$ 72	$ 68
Cash Surrender Value of Life Insurance	254	246
Corporate owned life insurance, borrowings	110	110
Ameren Illinois Company
Basis Of Presentation And Significant Accounting Policies [Line Items]
Cash Surrender Value of Life Insurance	120	118
Corporate owned life insurance, borrowings	110	$ 110
Partnership Funding Commitment
Basis Of Presentation And Significant Accounting Policies [Line Items]
Outstanding funding commitments	$ 17

Rate And Regulatory Matters (Na

Rate And Regulatory Matters (Narrative-Missouri) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2023 USD ($) numberOfCountriesInvestigatedByTheDOC	Sep. 30, 2022 USD ($)	Jun. 30, 2022 MWh	Mar. 31, 2022 USD ($) MWh
Rate And Regulatory Matters [Line Items]
Capital expenditures	$ 931			$ 774
Union Electric Company
Rate And Regulatory Matters [Line Items]
Capital expenditures	$ 481			$ 414
Missouri Renewable Energy Standard Percentage	15%
Missouri Renewable Energy Standard Percentage - Solar	2%
Number of Countries Investigated by the DOC | numberOfCountriesInvestigatedByTheDOC	4
Union Electric Company | Wind Generation Facility
Rate And Regulatory Matters [Line Items]
Amount of Megawatts | MWh			200	150
Capital expenditures	$ 350
Union Electric Company | Electric | Pending Rate Case
Rate And Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	140	$ 316
Union Electric Company | Electric | MEEIA 2024 [Domain]
Rate And Regulatory Matters [Line Items]
Energy efficiency investments in MEEIA 2024 programs	$ 122
Percentage of Energy Efficiency Goals Achieved	100%
Incentive Award if Energy Efficiency Goals Are Achieved	$ 55
Incentive Awards if Energy Efficiency Goals Are Exceeded	$ 14
Union Electric Company | Maximum
Rate And Regulatory Matters [Line Items]
Percentage of energy sourced from renewable resources	100%

Rate And Regulatory Matters (_2

Rate And Regulatory Matters (Narrative-Illinois) (Details) $ in Millions	3 Months Ended			12 Months Ended
	Jun. 30, 2023 USD ($)	Mar. 31, 2023 USD ($) numberOfProposedPerformanceMetrics	Mar. 31, 2022 USD ($)	Dec. 31, 2027 USD ($)	Dec. 31, 2026 USD ($)	Dec. 31, 2025 USD ($)	Dec. 31, 2024 USD ($)
Rate And Regulatory Matters [Line Items]
Revenues		$ 2,062	$ 1,879
Ameren Illinois Company
Rate And Regulatory Matters [Line Items]
Revenues		$ 1,101	$ 1,024
Ameren Illinois Company | Electric Distribution
Rate And Regulatory Matters [Line Items]
Number of Performance Metrics | numberOfProposedPerformanceMetrics		7
Requested Return on Equity Adjustment		0.24%
IETL | Ameren Illinois Company | Electric Distribution
Rate And Regulatory Matters [Line Items]
Public Utilities, Approved Equity Capital Structure, Percentage		50%
Amortization Period		2 years
Amortization Start Date		1 year
Multi-Year Rate Plan Reconciliation Cap		105%
IETL | Ameren Illinois Company | Electric Distribution | Subsequent Event
Rate And Regulatory Matters [Line Items]
Multi-year rate plan requested revenue requirement				$ 1,556	$ 1,477	$ 1,373	$ 1,282
Public Utilities, Requested Return on Equity, Percentage				10.50%	10.50%	10.50%	10.50%
Public Utilities, Requested Equity Capital Structure, Percentage				54.03%	54.02%	53.97%	53.99%
Rate Base				$ 5,300	$ 5,000	$ 4,600	$ 4,300
Public Utilities, Requested Rate Increase (Decrease), Percentage							50%
Public Utilities, Requested Rate Increase (Decrease), Amount							$ 171
IETL | Ameren Illinois Company | Electric Distribution | Minimum
Rate And Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Percentage		50%
Pending Rate Case | Ameren Illinois Company | Electric Distribution | Subsequent Event
Rate And Regulatory Matters [Line Items]
Public Utilities, Requested Equity Capital Structure, Percentage	53.99%
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 127
Pending Rate Case | Ameren Illinois Company | Natural gas
Rate And Regulatory Matters [Line Items]
Public Utilities, Requested Return on Equity, Percentage		10.70%
Public Utilities, Requested Equity Capital Structure, Percentage		53.99%
Rate Base		$ 2,900
Public Utilities, Requested Rate Increase (Decrease), Amount		160
Revenues		$ 77

Rate And Regulatory Matters (_3

Rate And Regulatory Matters (Narrative-Federal) (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	May 31, 2020	Mar. 31, 2023	Mar. 31, 2022
Rate And Regulatory Matters [Line Items]
ROE Change		0.50%
Revenues		$ 2,062	$ 1,879
Ameren Illinois Company
Rate And Regulatory Matters [Line Items]
Revenues		1,101	$ 1,024
Midwest Independent Transmission System Operator, Inc
Rate And Regulatory Matters [Line Items]
Revenues		19
Midwest Independent Transmission System Operator, Inc | Ameren Illinois Company
Rate And Regulatory Matters [Line Items]
Revenues		$ 13
Midwest Independent Transmission System Operator, Inc | Final Rate Order
Rate And Regulatory Matters [Line Items]
Approved return on equity percentage	10.02%

Short-Term Debt And Liquidity_2

Short-Term Debt And Liquidity (Narrative) (Details) $ in Billions	3 Months Ended
	Mar. 31, 2023 USD ($)	Mar. 31, 2022
Credit Agreements
Short-term Debt [Line Items]
Net Liquidity Available	$ 1.4
Actual debt-to-capital ratio	0.59
Utilities
Short-term Debt [Line Items]
Short-term Debt, Weighted Average Interest Rate, over Time	4.80%	0.39%
Union Electric Company | Missouri Credit Agreement
Short-term Debt [Line Items]
Actual debt-to-capital ratio	0.51
Ameren Illinois Company | Illinois Credit Agreement
Short-term Debt [Line Items]
Actual debt-to-capital ratio	0.45

Short-Term Debt and Liquidity_3

Short-Term Debt and Liquidity (Short-Term Debt outstanding) (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Short-term Debt [Line Items]
Short-term debt	$ 1,248	$ 1,070
Union Electric Company
Short-term Debt [Line Items]
Short-term debt	197	329
Ameren Illinois Company
Short-term Debt [Line Items]
Short-term debt	324	264
Commercial Paper
Short-term Debt [Line Items]
Short-term debt	1,248	1,070
Commercial Paper | Parent Company
Short-term Debt [Line Items]
Short-term debt	727	477
Commercial Paper | Union Electric Company
Short-term Debt [Line Items]
Short-term debt	197	329
Commercial Paper | Ameren Illinois Company
Short-term Debt [Line Items]
Short-term debt	$ 324	$ 264

Short-Term Debt and Liquidity_4

Short-Term Debt and Liquidity (Short-Term Debt Activity) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Short-term Debt [Line Items]
Average daily amount outstanding	$ 1,175	$ 789
Weighted-average interest rate	4.88%	0.41%
Short-term Debt, Maximum Amount Outstanding During Period	$ 1,381	$ 1,101
Peak interest rate	5.60%	1.15%
Parent Company
Short-term Debt [Line Items]
Average daily amount outstanding	$ 506	$ 282
Weighted-average interest rate	4.89%	0.41%
Short-term Debt, Maximum Amount Outstanding During Period	$ 728	$ 466
Peak interest rate	5.55%	1.05%
Union Electric Company
Short-term Debt [Line Items]
Average daily amount outstanding	$ 436	$ 408
Weighted-average interest rate	4.86%	0.44%
Short-term Debt, Maximum Amount Outstanding During Period	$ 592	$ 539
Peak interest rate	5.55%	1.06%
Ameren Illinois Company
Short-term Debt [Line Items]
Average daily amount outstanding	$ 233	$ 99
Weighted-average interest rate	4.89%	0.33%
Short-term Debt, Maximum Amount Outstanding During Period	$ 325	$ 142
Peak interest rate	5.60%	1.15%

Long-Term debt and Equity Fin_2

Long-Term debt and Equity Financings (Details) $ / shares in Units, shares in Thousands	1 Months Ended	3 Months Ended
	Apr. 30, 2023 $ / shares	Mar. 31, 2023 USD ($) $ / shares shares	Sep. 30, 2022 USD ($) shares	Mar. 31, 2022 USD ($) shares	Apr. 14, 2023 shares
Long-Term Debt And Equity Financings [Line Items]
Shares issued under the DRPlus and 401(k) plan | shares		100		100
Issuances of common stock		$ 5,000,000		$ 5,000,000
Stock Issued During Period, Shares, Other | shares		500	500	400
Stock Issued During Period, Value, Other			$ 37,000,000
Maximum Value Of Shares To Be Issued Under ATM Program		$ 980,000,000
Forward Contract Indexed to Issuer's Equity, Basis Spread		75
Subsequent Event
Long-Term Debt And Equity Financings [Line Items]
Forward Contract Indexed to Issuer's Equity, Indexed Shares (in shares) | shares					400
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share | $ / shares	$ 89.11
Minimum
Long-Term Debt And Equity Financings [Line Items]
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share | $ / shares		$ 89.31
Maximum
Long-Term Debt And Equity Financings [Line Items]
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share | $ / shares		94.80
Weighted Average
Long-Term Debt And Equity Financings [Line Items]
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share | $ / shares		$ 92.66
Dividend reinvestment and 401 (k) plans
Long-Term Debt And Equity Financings [Line Items]
Issuances of common stock		$ 5,000,000
Accrued Proceeds from Issuance of Common Stock		$ 7,000,000
Forward Sale Agreements Outstanding
Long-Term Debt And Equity Financings [Line Items]
Forward Contract Indexed to Issuer's Equity, Indexed Shares (in shares) | shares		3,800
Forward Contract Indexed to Issuer's Equity, Settlement Alternatives, Shares, at Fair Value | shares		3,400
Forward Contract Indexed to Issuer's Equity, Settlement Alternatives, Cash, at Fair Value		$ 317,000,000
Period End Net Cash Settlement Price		21,000,000
Period End Net Share Settlement Price		200,000
Forward Sale Agreement Equity Offering Shares		3,400,000
Forward Sale Agreement Gross Sales Price		321,000,000
Forward Sale Agreement, Compensation Received by Counterparty		3,000,000
Union Electric Company | Secured Debt | Senior Secured Notes 5.45% Due 2053
Long-Term Debt And Equity Financings [Line Items]
Debt Instrument, Face Amount		$ 500,000,000
Debt Instrument, Interest Rate, Stated Percentage		5.45%
Proceeds from Issuance of Secured Debt		$ 495,000,000

Other Income, Net (Details)

Other Income, Net (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Other Nonoperating Income (Expense) [Line Items]
Allowance for equity funds used during construction	$ 9	$ 8
Interest income on industrial development revenue bonds	1	6
Non-service cost components of net periodic benefit income	64	46
Miscellaneous income	9	4
Income (Loss) from Equity Method Investments	2	3
Donations	(2)	(2)
Miscellaneous expense	(5)	(5)
Total Other Income, Net	78	60
Union Electric Company
Other Nonoperating Income (Expense) [Line Items]
Allowance for equity funds used during construction	4	4
Interest income on industrial development revenue bonds	1	6
Non-service cost components of net periodic benefit income	14	14
Miscellaneous income	4	2
Donations	(1)	(1)
Miscellaneous expense	(3)	(2)
Total Other Income, Net	19	23
Defined Benefit Plan, Non-service Cost or Income Components - Tracker	17	6
Ameren Illinois Company
Other Nonoperating Income (Expense) [Line Items]
Allowance for equity funds used during construction	4	4
Non-service cost components of net periodic benefit income	31	21
Miscellaneous income	5	2
Donations	(1)	(1)
Miscellaneous expense	(2)	(2)
Total Other Income, Net	$ 37	$ 24

Derivative Financial Instrume_3

Derivative Financial Instruments (Derivative Instruments with Credit Risk-Related Contingent Features) (Details) $ in Millions	Mar. 31, 2023 USD ($)
Derivative [Line Items]
Aggregate Fair Value of Derivative Liabilities	$ 61
Cash Collateral Posted, Aggregate Fair Value	0
Potential Aggregate Amount of Additional Collateral Required	43
Union Electric Company
Derivative [Line Items]
Aggregate Fair Value of Derivative Liabilities	16
Cash Collateral Posted, Aggregate Fair Value	0
Potential Aggregate Amount of Additional Collateral Required	7
Ameren Illinois Company
Derivative [Line Items]
Aggregate Fair Value of Derivative Liabilities	45
Cash Collateral Posted, Aggregate Fair Value	0
Potential Aggregate Amount of Additional Collateral Required	$ 36

Derivative Financial Instrume_4

Derivative Financial Instruments (Open Gross Derivative Volumes By Commodity Type) (Detail) lb in Thousands, gal in Millions, MWh in Millions, MMBTU in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2023 MWh MMBTU lb gal	Dec. 31, 2022 MMBTU MWh lb gal
Fuel oils
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | gal	18	18
Natural gas
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure | MMBTU	245	205
Power
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure | MWh	7	7
Uranium
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass | lb	186	514
Union Electric Company | Fuel oils
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | gal	18	18
Union Electric Company | Natural gas
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure | MMBTU	60	48
Union Electric Company | Power
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure | MWh	1	1
Union Electric Company | Uranium
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass | lb	186	514
Ameren Illinois Company | Fuel oils
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | gal	0	0
Ameren Illinois Company | Natural gas
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure | MMBTU	185	157
Ameren Illinois Company | Power
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure | MWh	6	6
Ameren Illinois Company | Uranium
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass | lb	0	0

Derivative Financial Instrume_5

Derivative Financial Instruments (Derivative Instruments Carrying Value) (Detail) - Not Designated As Hedging Instrument - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Derivative [Line Items]
Derivative assets	$ 39	$ 89
Derivative Liability	130	136
Fuel oils | Other current assets
Derivative [Line Items]
Derivative assets	8	13
Fuel oils | Other assets
Derivative [Line Items]
Derivative assets	2	3
Fuel oils | Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	1	0
Natural gas | Other current assets
Derivative [Line Items]
Derivative assets	6	30
Natural gas | Other assets
Derivative [Line Items]
Derivative assets	16	20
Natural gas | Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	17	11
Natural gas | Other current liabilities
Derivative [Line Items]
Derivative Liability	42	27
Power | Other current assets
Derivative [Line Items]
Derivative assets	5	16
Power | Other assets
Derivative [Line Items]
Derivative assets	1	4
Power | Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	43	37
Power | Other current liabilities
Derivative [Line Items]
Derivative Liability	27	61
Uranium | Other current assets
Derivative [Line Items]
Derivative assets	1	2
Uranium | Other assets
Derivative [Line Items]
Derivative assets	0	1
Union Electric Company
Derivative [Line Items]
Derivative assets	25	49
Derivative Liability	32	68
Union Electric Company | Fuel oils | Other current assets
Derivative [Line Items]
Derivative assets	8	13
Union Electric Company | Fuel oils | Other assets
Derivative [Line Items]
Derivative assets	2	3
Union Electric Company | Fuel oils | Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	1	0
Union Electric Company | Natural gas | Other current assets
Derivative [Line Items]
Derivative assets	1	7
Union Electric Company | Natural gas | Other assets
Derivative [Line Items]
Derivative assets	8	9
Union Electric Company | Natural gas | Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	5	2
Union Electric Company | Natural gas | Other current liabilities
Derivative [Line Items]
Derivative Liability	9	7
Union Electric Company | Power | Other current assets
Derivative [Line Items]
Derivative assets	5	14
Union Electric Company | Power | Other assets
Derivative [Line Items]
Derivative assets	0	0
Union Electric Company | Power | Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	0	0
Union Electric Company | Power | Other current liabilities
Derivative [Line Items]
Derivative Liability	17	59
Union Electric Company | Uranium | Other current assets
Derivative [Line Items]
Derivative assets	1	2
Union Electric Company | Uranium | Other assets
Derivative [Line Items]
Derivative assets	0	1
Ameren Illinois Company
Derivative [Line Items]
Derivative assets	14	40
Derivative Liability	98	68
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 deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	0	0
Ameren Illinois Company | Natural gas | Other current assets
Derivative [Line Items]
Derivative assets	5	23
Ameren Illinois Company | Natural gas | Other assets
Derivative [Line Items]
Derivative assets	8	11
Ameren Illinois Company | Natural gas | Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	12	9
Ameren Illinois Company | Natural gas | Other current liabilities
Derivative [Line Items]
Derivative Liability	33	20
Ameren Illinois Company | Power | Other current assets
Derivative [Line Items]
Derivative assets	0	2
Ameren Illinois Company | Power | Other assets
Derivative [Line Items]
Derivative assets	1	4
Ameren Illinois Company | Power | Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	43	37
Ameren Illinois Company | Power | Other current liabilities
Derivative [Line Items]
Derivative Liability	10	2
Ameren Illinois Company | Uranium | Other current assets
Derivative [Line Items]
Derivative assets	0	0
Ameren Illinois Company | Uranium | Other assets
Derivative [Line Items]
Derivative assets	$ 0	$ 0

Derivative Financial Instrume_6

Derivative Financial Instruments (Offsetting Assets and Liabilities) (Details) - Not Designated As Hedging Instrument - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Derivative [Line Items]
Gross derivative asset amount recognized on the balance sheet	$ 39	$ 89
Gross derivative instruments not offset in the balance sheet	20	29
Gross cash collateral received not offset in the balance sheet	0	0
Net derivative asset	19	60
Gross derivative liability amount recognized on the balance sheet	130	136
Gross derivative instruments not offset in the balance sheet	20	29
Gross cash collateral posted not offset in the balance sheet	16	56
Net derivative liability	94	51
Union Electric Company
Derivative [Line Items]
Gross derivative asset amount recognized on the balance sheet	25	49
Gross derivative instruments not offset in the balance sheet	9	9
Gross cash collateral received not offset in the balance sheet	0	0
Net derivative asset	16	40
Gross derivative liability amount recognized on the balance sheet	32	68
Gross derivative instruments not offset in the balance sheet	9	9
Gross cash collateral posted not offset in the balance sheet	16	56
Net derivative liability	7	3
Ameren Illinois Company
Derivative [Line Items]
Gross derivative asset amount recognized on the balance sheet	14	40
Gross derivative instruments not offset in the balance sheet	11	20
Gross cash collateral received not offset in the balance sheet	0	0
Net derivative asset	3	20
Gross derivative liability amount recognized on the balance sheet	98	68
Gross derivative instruments not offset in the balance sheet	11	20
Gross cash collateral posted not offset in the balance sheet	0	0
Net derivative liability	$ 87	$ 48

Fair Value Measurements (Schedu

Fair Value Measurements (Schedule Of Fair Value Hierarchy Of Assets And Liabilities Measured At Fair Value On Recurring Basis) (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	$ 1,014	$ 947
Assets fair value	1,053	1,036
Excluded receivables, payables, and accrued income, net	5	11
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	668	618
Assets fair value	678	636
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	346	329
Assets fair value	365	372
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Assets fair value	10	28
Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	39	89
Derivative Liability	130	136
Commodity Contract | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	10	18
Derivative Liability	19	57
Commodity Contract | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	19	43
Derivative Liability	47	25
Commodity Contract | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	10	28
Derivative Liability	64	54
Union Electric Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	1,014	947
Assets fair value	1,039	996
Union Electric Company | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	668	618
Assets fair value	678	635
Union Electric Company | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	346	329
Assets fair value	355	344
Union Electric Company | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Assets fair value	6	17
Union Electric Company | Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	25	49
Derivative Liability	32	68
Union Electric Company | Commodity Contract | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	10	17
Derivative Liability	18	57
Union Electric Company | Commodity Contract | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	9	15
Derivative Liability	11	6
Union Electric Company | Commodity Contract | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	6	17
Derivative Liability	3	5
Union Electric Company | Fuel oils | Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	10	16
Derivative Liability	1	0
Union Electric Company | Fuel oils | Commodity Contract | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	10	16
Derivative Liability	1	0
Union Electric Company | Fuel oils | Commodity Contract | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Derivative Liability	0	0
Union Electric Company | Fuel oils | Commodity Contract | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Derivative Liability	0	0
Union Electric Company | Natural gas | Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	9	16
Derivative Liability	14	9
Union Electric Company | Natural gas | Commodity Contract | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	1
Derivative Liability	0	0
Union Electric Company | Natural gas | Commodity Contract | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	9	15
Derivative Liability	11	6
Union Electric Company | Natural gas | Commodity Contract | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Derivative Liability	3	3
Union Electric Company | Power | Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	5	14
Derivative Liability	17	59
Union Electric Company | Power | Commodity Contract | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Derivative Liability	17	57
Union Electric Company | Power | Commodity Contract | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Derivative Liability	0	0
Union Electric Company | Power | Commodity Contract | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	5	14
Derivative Liability	0	2
Union Electric Company | Uranium | Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	1	3
Union Electric Company | Uranium | Commodity Contract | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Union Electric Company | Uranium | Commodity Contract | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Union Electric Company | Uranium | Commodity Contract | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	1	3
Union Electric Company | Equity securities: | U.S. large capitalization
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	668	618
Union Electric Company | Equity securities: | U.S. large capitalization | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	668	618
Union Electric Company | Equity securities: | U.S. large capitalization | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Union Electric Company | Equity securities: | U.S. large capitalization | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Union Electric Company | Debt securities: | U.S. Treasury and agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	149	137
Union Electric Company | Debt securities: | U.S. Treasury and agency securities | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Union Electric Company | Debt securities: | U.S. Treasury and agency securities | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	149	137
Union Electric Company | Debt securities: | U.S. Treasury and agency securities | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Union Electric Company | Debt securities: | Corporate bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	123	122
Union Electric Company | Debt securities: | Corporate bonds | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Union Electric Company | Debt securities: | Corporate bonds | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	123	122
Union Electric Company | Debt securities: | Corporate bonds | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Union Electric Company | Debt securities: | Other Debt Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	74	70
Union Electric Company | Debt securities: | Other Debt Securities | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Union Electric Company | Debt securities: | Other Debt Securities | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	74	70
Union Electric Company | Debt securities: | Other Debt Securities | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Ameren Illinois Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets fair value	14	40
Ameren Illinois Company | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets fair value	0	1
Ameren Illinois Company | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets fair value	10	28
Ameren Illinois Company | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets fair value	4	11
Ameren Illinois Company | Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liability	98	68
Ameren Illinois Company | Commodity Contract | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liability	1	0
Ameren Illinois Company | Commodity Contract | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liability	36	19
Ameren Illinois Company | Commodity Contract | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liability	61	49
Ameren Illinois Company | Natural gas | Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	13	34
Derivative Liability	45	29
Ameren Illinois Company | Natural gas | Commodity Contract | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	1
Derivative Liability	1	0
Ameren Illinois Company | Natural gas | Commodity Contract | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	10	28
Derivative Liability	36	19
Ameren Illinois Company | Natural gas | Commodity Contract | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	3	5
Derivative Liability	8	10
Ameren Illinois Company | Power | Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	1	6
Derivative Liability	53	39
Ameren Illinois Company | Power | Commodity Contract | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Derivative Liability	0	0
Ameren Illinois Company | Power | Commodity Contract | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Derivative Liability	0	0
Ameren Illinois Company | Power | Commodity Contract | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	1	6
Derivative Liability	$ 53	$ 39

Fair Value Measurements (Sche_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) (Details) - Power - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ (21)	$ (132)
Included in regulatory assets/liabilities	(26)	1
Settlements, assets	0	4
Change in unrealized gains (losses) related to assets/liabilities held at period end	(20)	4
Ending balance	(47)	(127)
Union Electric Company
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	12	(15)
Included in regulatory assets/liabilities	(6)	(41)
Settlements, assets		3
Settlement, liabilities	(1)
Change in unrealized gains (losses) related to assets/liabilities held at period end	(2)	(38)
Ending balance	5	(53)
Ameren Illinois Company
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	(33)	(117)
Included in regulatory assets/liabilities	(20)	42
Settlements, assets	1	1
Change in unrealized gains (losses) related to assets/liabilities held at period end	(18)	42
Ending balance	$ (52)	$ (74)

Fair Value Measurements (Sche_3

Fair Value Measurements (Schedule Of Valuation Process And Unobservable Inputs) (Details) - Power $ in Millions	Mar. 31, 2023 USD ($) $ / MWh	Dec. 31, 2022 USD ($) $ / MWh $ / MMBTU
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative assets | $	$ 6	$ 20
Derivative liabilities | $	$ (53)	$ (41)
Commodity Forward Price | Discounted cash flow | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Measurement input	22	38
Commodity Forward Price | Discounted cash flow | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Measurement input	74	89
Commodity Forward Price | Discounted cash flow | Weighted Average
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Measurement input	46	51
Nodal Basis | Discounted cash flow | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Measurement input	(9)	(10)
Nodal Basis | Discounted cash flow | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Measurement input	(1)	(1)
Nodal Basis | Discounted cash flow | Weighted Average
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Measurement input	(4)	(4)
Commodity Future Price | Discounted cash flow | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative Asset (Liability) Net, Measurement Input [Extensible Enumeration]	Commodity Future Price
Commodity Future Price | Discounted cash flow | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative Asset (Liability) Net, Measurement Input [Extensible Enumeration]	Commodity Future Price
Commodity Future Price | Discounted cash flow | Weighted Average
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Measurement input | $ / MMBTU		0

Fair Value Measurements (Sche_4

Fair Value Measurements (Schedule Of Carrying Amounts And Estimated Fair Values Of Financial Assets and Liabilities) (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022	Dec. 31, 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	$ 237	$ 216	$ 154	$ 155
Short-term debt	1,248	1,070
Union Electric Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	11	13	9	8
Short-term debt	197	329
Ameren Illinois Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	217	191	$ 137	$ 133
Short-term debt	324	264
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	237	216
Investments in industrial development revenue bonds		240
Short-term debt	1,248	1,070
Long-term debt (including current portion)	14,281	14,025
Debt Issuance Costs, Net	103	99
Carrying Amount | Union Electric Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	11	13
Investments in industrial development revenue bonds		240
Short-term debt	197	329
Long-term debt (including current portion)	6,341	6,086
Debt Issuance Costs, Net	45	41
Carrying Amount | Ameren Illinois Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	217	191
Short-term debt	324	264
Long-term debt (including current portion)	4,836	4,835
Debt Issuance Costs, Net	44	44
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	237	216
Investments, Fair Value Disclosure		240
Short-term Debt, Fair Value	1,248	1,070
Long-term Debt, Fair Value	12,881	12,453
Fair Value | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	237	216
Investments, Fair Value Disclosure		0
Short-term Debt, Fair Value	0	0
Long-term Debt, Fair Value	0	0
Fair Value | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	0	0
Investments, Fair Value Disclosure		240
Short-term Debt, Fair Value	1,248	1,070
Long-term Debt, Fair Value	12,408	11,989
Fair Value | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	0	0
Investments, Fair Value Disclosure		0
Short-term Debt, Fair Value	0	0
Long-term Debt, Fair Value	473	464
Fair Value | Union Electric Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	11	13
Investments, Fair Value Disclosure		240
Short-term Debt, Fair Value	197	329
Long-term Debt, Fair Value	5,706	5,365
Fair Value | Union Electric Company | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	11	13
Investments, Fair Value Disclosure		0
Short-term Debt, Fair Value	0	0
Long-term Debt, Fair Value	0	0
Fair Value | Union Electric Company | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	0	0
Investments, Fair Value Disclosure		240
Short-term Debt, Fair Value	197	329
Long-term Debt, Fair Value	5,706	5,365
Fair Value | Union Electric Company | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	0	0
Investments, Fair Value Disclosure		0
Short-term Debt, Fair Value	0	0
Long-term Debt, Fair Value	0	0
Fair Value | Ameren Illinois Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	217	191
Short-term Debt, Fair Value	324	264
Long-term Debt, Fair Value	4,368	4,320
Fair Value | Ameren Illinois Company | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	217	191
Short-term Debt, Fair Value	0	0
Long-term Debt, Fair Value	0	0
Fair Value | Ameren Illinois Company | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	0	0
Short-term Debt, Fair Value	324	264
Long-term Debt, Fair Value	4,368	4,320
Fair Value | Ameren Illinois Company | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	0	0
Short-term Debt, Fair Value	0	0
Long-term Debt, Fair Value	$ 0	$ 0

Related Party Transactions (Nar

Related Party Transactions (Narrative) (Details) - Ameren Services Support Services Agreement - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Union Electric Company
Related Party Transaction [Line Items]
Due from Related Parties	$ 36	$ 41
Ameren Illinois Company
Related Party Transaction [Line Items]
Due from Related Parties	$ 39	$ 43

Related Party Transactions (Sch

Related Party Transactions (Schedule of Affiliate Receivables and Payables) (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Union Electric Company
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	$ 36	$ 43
Accounts Receivable, Related Parties, Current	70	51
Union Electric Company | Income taxes payable to parent
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	0	0
Union Electric Company | Income taxes receivable from parent
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties, Current	54	39
Ameren Illinois Company
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	117	93
Accounts Receivable, Related Parties, Current	14	12
Ameren Illinois Company | Income taxes payable to parent
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	80	50
Ameren Illinois Company | Income taxes receivable from parent
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties, Current	$ 0	$ 0

Related Party Transactions (Eff

Related Party Transactions (Effects of Related-party Transactions on the Statement of Income) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Union Electric Company | Ameren Missouri Power Supply Agreements with Ameren Illinois
Related Party Transaction [Line Items]
Operating Revenues	$ 1	$ 4
Union Electric Company | Ameren Missouri and Ameren Illinois Rent and Facility Services
Related Party Transaction [Line Items]
Operating Revenues	10	6
Operating Expenses	1	1
Union Electric Company | Ameren Missouri and Ameren Illinois Miscellaneous Support Services
Related Party Transaction [Line Items]
Operating Revenues	1	1
Union Electric Company | Total Related Party Operating Revenues
Related Party Transaction [Line Items]
Operating Revenues	10	10
Union Electric Company | Ameren Missouri and Ameren Illinois Transmission Services from ATXI
Related Party Transaction [Line Items]
Operating Expenses	1	1
Union Electric Company | Purchased Power
Related Party Transaction [Line Items]
Operating Expenses	1	1
Union Electric Company | Ameren Services Support Services Agreement
Related Party Transaction [Line Items]
Operating Expenses	35	38
Union Electric Company | Total Related Party Other Operations and Maintenance
Related Party Transaction [Line Items]
Operating Expenses	35	38
Union Electric Company | Money pool borrowings (advances)
Related Party Transaction [Line Items]
Interest Charges (Income)	1	1
Ameren Illinois Company | Ameren Missouri and Ameren Illinois Rent and Facility Services
Related Party Transaction [Line Items]
Operating Revenues	1	1
Operating Expenses	2	1
Ameren Illinois Company | Ameren Missouri and Ameren Illinois Miscellaneous Support Services
Related Party Transaction [Line Items]
Operating Revenues	1	1
Ameren Illinois Company | Total Related Party Operating Revenues
Related Party Transaction [Line Items]
Operating Revenues	1	1
Ameren Illinois Company | Ameren Illinois Power Supply Agreements with Ameren Missouri
Related Party Transaction [Line Items]
Operating Expenses	1	4
Ameren Illinois Company | Ameren Missouri and Ameren Illinois Transmission Services from ATXI
Related Party Transaction [Line Items]
Operating Expenses	1	1
Ameren Illinois Company | Purchased Power
Related Party Transaction [Line Items]
Operating Expenses	1	4
Ameren Illinois Company | Ameren Services Support Services Agreement
Related Party Transaction [Line Items]
Operating Expenses	35	35
Ameren Illinois Company | Total Related Party Other Operations and Maintenance
Related Party Transaction [Line Items]
Operating Expenses	37	36
Ameren Illinois Company | Money pool borrowings (advances)
Related Party Transaction [Line Items]
Interest Charges (Income)	$ 1	$ 1

Commitments And Contingencies (

Commitments And Contingencies (Environmental Matters) (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2023 USD ($) scrubber site	Dec. 31, 2022 USD ($)
Loss Contingencies [Line Items]
Asset Retirement Obligation	$ 792	$ 786
Minimum
Loss Contingencies [Line Items]
Estimated capital costs to comply with existing and known federal and state air emissions regulations	90
Maximum
Loss Contingencies [Line Items]
Estimated capital costs to comply with existing and known federal and state air emissions regulations	$ 120
Union Electric Company
Loss Contingencies [Line Items]
Number of Energy Center Scrubbers | scrubber	2
Asset Retirement Obligation	$ 788	782
Union Electric Company | Coal Fired Electric Generation Equipment
Loss Contingencies [Line Items]
Plant To Be Abandoned, Net	600
Union Electric Company | Minimum
Loss Contingencies [Line Items]
Estimated capital costs to comply with existing and known federal and state air emissions regulations	90
Union Electric Company | Maximum
Loss Contingencies [Line Items]
Estimated capital costs to comply with existing and known federal and state air emissions regulations	120
Ameren Illinois Company
Loss Contingencies [Line Items]
Asset Retirement Obligation	4	$ 4
Manufactured Gas Plant
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies	$ 58
Manufactured Gas Plant | Ameren Illinois Company
Loss Contingencies [Line Items]
Number of remediation sites | site	44
Accrual for environmental loss contingencies	$ 58
Manufactured Gas Plant | Ameren Illinois Company | Minimum
Loss Contingencies [Line Items]
Estimate of possible loss	58
Manufactured Gas Plant | Ameren Illinois Company | Maximum
Loss Contingencies [Line Items]
Estimate of possible loss	108
Rush Island Energy Center | Union Electric Company
Loss Contingencies [Line Items]
Rate Base	400
New CCR Rules Estimate
Loss Contingencies [Line Items]
Asset Retirement Obligation	48
New CCR Rules Estimate | Union Electric Company
Loss Contingencies [Line Items]
Asset Retirement Obligation	$ 48

Callaway Energy Center (Insuran

Callaway Energy Center (Insurance Disclosure) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2023 USD ($) yr
Nuclear Waste Matters [Line Items]
Decommissioning Cost	$ 7
Frequency of Decommissioning Cost Study	3 years
Number Of Years The Limit Of Liability And The Maximum Potential Annual Payments Are Adjusted	5 years
Number Of Weeks Of Coverage After The First Twelve Weeks Of An Outage | yr	1
Number Of Additional Weeks After Initial Indemnity Coverage For Power Outage | yr	1.365
Public Liability And Nuclear Worker Liability - American Nuclear Insurers
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	$ 450
Insurance Maximum Coverage per Incident	0
Public Liability And Nuclear Worker Liability - Pool Participation
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	13,210
Insurance Maximum Coverage per Incident	138
Threshold Amount For Retrospective Insurance Assessment For Covered Loss Under Public Liability And Nuclear Worker Liability Insurance Policy	450
Maximum Annual Payment Per Incident At Licensed Commercial Nuclear Reactor	21
Public Liability
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	13,660
Insurance Maximum Coverage per Incident	138
Property Damage - Nuclear Electric Insurance Ltd
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	3,200
Insurance Maximum Coverage per Incident	28
Accidental Outage - Nuclear Electric Insurance Ltd
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	490
Insurance Maximum Coverage per Incident	9
Amount Of Weekly Indemnity Coverage Commencing Twelve Weeks After Power Outage	4.5
Amount Of Additional Weekly Indemnity Coverage Commencing After Initial Indemnity Coverage	3.6
Amount Of Weekly Indemnity Coverage Thereafter Not Exceeding Policy Limit	490
Sub-Limit Of Amount Of Weekly Indemnity Coverage Thereafter Not Exceeding Policy Limit For Non-Nuclear Events	328
Radiation Event
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	2,700
Aggregate Nuclear Power Industry Insurance Policy Limit For Losses From Terrorist Attacks Within Twelve Month Period	3,200
Non-Radiation Event
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	2,300
Aggregate Nuclear Power Industry Insurance Policy Limit For Losses From Terrorist Attacks Within Twelve Month Period	1,800
Property Damage European Mutual Association for Nuclear Insurance
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	$ 490

Retirement Benefits (Components

Retirement Benefits (Components Of Net Periodic Benefit Cost) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total non-service cost components	$ (64)	$ (46)
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	23	33
Interest cost	55	40
Expected return on plan assets(b)	(83)	(80)
Prior service benefit	0	0
Actuarial loss (gain)	(29)	6
Total non-service cost components	(57)	(34)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Total	$ (34)	(1)
Defined Benefit Plan, Amortization Period of Actuarial Gain (Loss)	10 years
Defined Benefit Plan, Difference Between Actual and Expected Return (Loss) on Plan Assets Amortization Period	4 years
Other Postretirement Benefit Plan, Defined Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	$ 3	5
Interest cost	11	8
Expected return on plan assets(b)	(23)	(21)
Prior service benefit	(1)	(1)
Actuarial loss (gain)	(11)	(4)
Total non-service cost components	(24)	(18)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Total	$ (21)	$ (13)
Defined Benefit Plan, Amortization Period of Actuarial Gain (Loss)	10 years
Defined Benefit Plan, Difference Between Actual and Expected Return (Loss) on Plan Assets Amortization Period	4 years

Retirement Benefits (Summary of

Retirement Benefits (Summary of Benefit Plan Costs Incurred) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	$ (34)	$ (1)
Pension Plan | Union Electric Company
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	(18)	(1)
Pension Plan | Ameren Illinois Company
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	(14)	1
Pension Plan | Other Affiliated Entities And Intercompany Eliminations
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	(2)	(1)
Other Postretirement Benefit Plan, Defined Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	(21)	(13)
Other Postretirement Benefit Plan, Defined Benefit | Union Electric Company
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	(8)	(3)
Other Postretirement Benefit Plan, Defined Benefit | Ameren Illinois Company
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	(13)	(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]
Net periodic benefit cost	$ 0	$ 0

Income Taxes (Schedule of Effec

Income Taxes (Schedule of Effective Income Tax Rate Reconciliation) (Details)	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Income Taxes [Line Items]
Federal statutory corporate income tax rate	21%	21%
Increases (decreases) from:
Amortization of deferred investment tax credit	0%	0%
Amortization of excess deferred taxes	(8.00%)	(8.00%)
Renewable and other tax credits	(5.00%)	(5.00%)
State tax	6%	5%
Stock-based compensation	(1.00%)	(1.00%)
Other permanent items	(1.00%)	0%
Effective income tax rate	12%	12%
Union Electric Company
Income Taxes [Line Items]
Federal statutory corporate income tax rate	21%	21%
Increases (decreases) from:
Amortization of deferred investment tax credit	0%	(1.00%)
Amortization of excess deferred taxes	(16.00%)	(16.00%)
Renewable and other tax credits	(10.00%)	(11.00%)
State tax	4%	3%
Stock-based compensation	0%	0%
Other permanent items	(3.00%)	0%
Effective income tax rate	(4.00%)	(4.00%)
Ameren Illinois Company
Income Taxes [Line Items]
Federal statutory corporate income tax rate	21%	21%
Increases (decreases) from:
Amortization of deferred investment tax credit	0%	0%
Amortization of excess deferred taxes	(2.00%)	(2.00%)
Renewable and other tax credits	0%	0%
State tax	7%	7%
Stock-based compensation	0%	0%
Other permanent items	(1.00%)	0%
Effective income tax rate	25%	26%

Supplemental Information (Cash

Supplemental Information (Cash and Cash Equivalents) (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022	Dec. 31, 2021
Schedule of Cash and Cash Equivalents Including Restricted Cash [Line Items]
Cash and cash equivalents	$ 10	$ 10
Restricted cash included in “Other current assets”	13	13
Restricted cash included in “Other assets”	211	185
Restricted cash included in “Nuclear decommissioning trust fund”	3	8
Total cash, cash equivalents, and restricted cash	237	216	$ 154	$ 155
Union Electric Company
Schedule of Cash and Cash Equivalents Including Restricted Cash [Line Items]
Cash and cash equivalents	3	0
Restricted cash included in “Other current assets”	5	5
Restricted cash included in “Other assets”	0	0
Restricted cash included in “Nuclear decommissioning trust fund”	3	8
Total cash, cash equivalents, and restricted cash	11	13	9	8
Ameren Illinois Company
Schedule of Cash and Cash Equivalents Including Restricted Cash [Line Items]
Cash and cash equivalents	0	0
Restricted cash included in “Other current assets”	6	6
Restricted cash included in “Other assets”	211	185
Restricted cash included in “Nuclear decommissioning trust fund”	0	0
Total cash, cash equivalents, and restricted cash	$ 217	$ 191	$ 137	$ 133

Supplemental Information (Allow

Supplemental Information (Allowance for Doubtful Accounts) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Allowance for Doubtful Accounts Receivable [Roll Forward]
Beginning of period	$ 31	$ 29
Bad debt expense	10	4
Net write-offs	(7)	(5)
End of period	34	$ 28
Payables for purchased receivables	$ 35		$ 31
Percentage of accounts receivable balances that are 30 days past due or are part of a deferred payment arrangement	23%	20%
Accounts receivable balances that are 30 days or more past due or part of a deferred payment arrangement	$ 153	$ 116
Union Electric Company
Allowance for Doubtful Accounts Receivable [Roll Forward]
Beginning of period	13	13
Bad debt expense	2	1
Net write-offs	(3)	(3)
End of period	$ 12	$ 11
Percentage of accounts receivable balances that are 30 days past due or are part of a deferred payment arrangement	15%	15%
Accounts receivable balances that are 30 days or more past due or part of a deferred payment arrangement	$ 33	$ 31
Ameren Illinois Company
Allowance for Doubtful Accounts Receivable [Roll Forward]
Beginning of period	18	16
Bad debt expense	8	3
Net write-offs	(4)	(2)
End of period	22	$ 17
Payables for purchased receivables	$ 35		$ 31
Percentage of accounts receivable balances that are 30 days past due or are part of a deferred payment arrangement	28%	23%
Accounts receivable balances that are 30 days or more past due or part of a deferred payment arrangement	$ 120	$ 85

Supplemental Information (Suppl

Supplemental Information (Supplemental Cash Flow Information) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Supplemental Cash Flow Information [Line Items]
Accrued capital expenditures	$ 298	$ 345
Net realized and unrealized gain/(loss) – nuclear decommissioning trust fund	54	(71)
Return on investment in industrial development revenue bonds	240	0
Termination of a financing obligation(a)	240	0
Issuance of common stock for stock-based compensation
Supplemental Cash Flow Information [Line Items]
Stock Issued	37	31
Issuance of common stock under the DRPlus
Supplemental Cash Flow Information [Line Items]
Stock Issued	7	8
Union Electric Company
Supplemental Cash Flow Information [Line Items]
Accrued capital expenditures	153	194
Net realized and unrealized gain/(loss) – nuclear decommissioning trust fund	54	(71)
Return on investment in industrial development revenue bonds	240	0
Termination of a financing obligation(a)	240	0
Union Electric Company | Issuance of common stock for stock-based compensation
Supplemental Cash Flow Information [Line Items]
Stock Issued	0	0
Union Electric Company | Issuance of common stock under the DRPlus
Supplemental Cash Flow Information [Line Items]
Stock Issued	0	0
Ameren Illinois Company
Supplemental Cash Flow Information [Line Items]
Accrued capital expenditures	138	147
Net realized and unrealized gain/(loss) – nuclear decommissioning trust fund	0	0
Return on investment in industrial development revenue bonds	0	0
Termination of a financing obligation(a)	0	0
Ameren Illinois Company | Issuance of common stock for stock-based compensation
Supplemental Cash Flow Information [Line Items]
Stock Issued	0	0
Ameren Illinois Company | Issuance of common stock under the DRPlus
Supplemental Cash Flow Information [Line Items]
Stock Issued	$ 0	$ 0

Supplemental Information (Sched

Supplemental Information (Schedule of Asset Retirement Obligations) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Dec. 31, 2022
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Beginning Balance	$ 786
Liabilities settled	(2)
Accretion	8
Asset Retirement Obligation, Ending Balance	792
Other current liabilities	745	$ 797
Union Electric Company
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Beginning Balance	782
Liabilities settled	(2)
Accretion	8
Asset Retirement Obligation, Ending Balance	788
Other current liabilities	187	260
Ameren Illinois Company
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Beginning Balance	4
Liabilities settled	0
Accretion	0
Asset Retirement Obligation, Ending Balance	4
Other current liabilities	398	383
Asset Retirement Obligation Balance
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Other current liabilities	23	23
Asset Retirement Obligation Balance | Union Electric Company
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Other current liabilities	$ 23	$ 23

Supplemental Information (Narra

Supplemental Information (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Effective Income Tax Rate Reconciliation, Share-based Compensation, Excess Tax Benefit, Amount	$ 6	$ 5
Deferred Compensation Liability, Classified, Noncurrent	$ 85		$ 87
Q1 2023 Issuance
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	3 years
Performance Shares | Q1 2023 Issuance
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)	265,422
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Granted in Period, Fair Value	$ 24
Stock Issued During Period Percentage Conversion Of Units, Low End	0%
Stock Issued During Period Percentage Conversion Of Units, High End	200%
Performance Shares | Market performance measures achievement | Q1 2023 Issuance
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)	227,494
Performance Shares | Renewable generation and energy storage installation targets | Q1 2023 Issuance
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)	37,928
Restricted Stock Units (RSUs) | Q1 2023 Issuance
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)	116,701
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Granted in Period, Fair Value	$ 10

Supplemental Information (Sch_2

Supplemental Information (Schedule Of Excise Taxes) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Accounting Policies [Line Items]
Excise tax expense	$ 71	$ 79
Union Electric Company
Accounting Policies [Line Items]
Excise tax expense	34	34
Ameren Illinois Company
Accounting Policies [Line Items]
Excise tax expense	$ 37	$ 45

Supplemental Information (Earni

Supplemental Information (Earnings Per Share) (Details) - shares	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Earnings Per Share Reconciliation [Abstract]
Weighted-average Common Shares Outstanding – Basic	262,200,000	257,900,000
Assumed settlement of performance share units and restricted stock units	900,000	1,100,000
Weighted-average Common Shares Outstanding – Diluted	263,100,000	259,000,000
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in shares)	0	0

Segment Information (Schedule O

Segment Information (Schedule Of Segment Reporting Information By Segment) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Segment Reporting Information [Line Items]
Revenues	$ 2,062	$ 1,879
Net income (loss) attributable to common shareholders	264	252
Capital expenditures	931	774
Union Electric Company
Segment Reporting Information [Line Items]
Revenues	923	818
Net income (loss) attributable to common shareholders	28	50
Ameren Illinois Company
Segment Reporting Information [Line Items]
Revenues	1,101	1,024
Net income (loss) attributable to common shareholders	198	169
Capital expenditures	407	342
Operating Segments | Union Electric Company
Segment Reporting Information [Line Items]
Revenues	913	808
Net income (loss) attributable to common shareholders	28	50
Capital expenditures	481	414
Operating Segments | Ameren Illinois Electric Distribution
Segment Reporting Information [Line Items]
Revenues	624	464
Net income (loss) attributable to common shareholders	61	49
Capital expenditures	170	138
Operating Segments | Ameren Illinois Natural Gas
Segment Reporting Information [Line Items]
Revenues	391	481
Net income (loss) attributable to common shareholders	87	80
Capital expenditures	51	49
Operating Segments | Ameren Transmission
Segment Reporting Information [Line Items]
Revenues	134	126
Net income (loss) attributable to common shareholders	71	58
Capital expenditures	213	172
Operating Segments | Ameren Illinois Company | Ameren Illinois Electric Distribution
Segment Reporting Information [Line Items]
Revenues	624	465
Net income (loss) attributable to common shareholders	61	49
Capital expenditures	170	138
Operating Segments | Ameren Illinois Company | Ameren Illinois Natural Gas
Segment Reporting Information [Line Items]
Revenues	391	481
Net income (loss) attributable to common shareholders	87	80
Capital expenditures	51	49
Operating Segments | Ameren Illinois Company | Ameren Illinois Transmission
Segment Reporting Information [Line Items]
Revenues	86	78
Net income (loss) attributable to common shareholders	50	40
Capital expenditures	186	155
Other
Segment Reporting Information [Line Items]
Net income (loss) attributable to common shareholders	17	15
Capital expenditures	3	2
Intersegment Eliminations
Segment Reporting Information [Line Items]
Intersegment revenues	(39)	(31)
Capital expenditures	13	(1)
Intersegment Eliminations | Union Electric Company
Segment Reporting Information [Line Items]
Intersegment revenues	(10)	(10)
Intersegment Eliminations | Ameren Illinois Electric Distribution
Segment Reporting Information [Line Items]
Intersegment revenues	0	(1)
Intersegment Eliminations | Ameren Illinois Natural Gas
Segment Reporting Information [Line Items]
Intersegment revenues	0	0
Intersegment Eliminations | Ameren Transmission
Segment Reporting Information [Line Items]
Intersegment revenues	(29)	(20)
Intersegment Eliminations | Ameren Illinois Company
Segment Reporting Information [Line Items]
Intersegment revenues	(28)	(20)
Intersegment Eliminations | Ameren Illinois Company | Ameren Illinois Electric Distribution
Segment Reporting Information [Line Items]
Intersegment revenues	0	0
Intersegment Eliminations | Ameren Illinois Company | Ameren Illinois Natural Gas
Segment Reporting Information [Line Items]
Intersegment revenues	0	0
Intersegment Eliminations | Ameren Illinois Company | Ameren Illinois Transmission
Segment Reporting Information [Line Items]
Intersegment revenues	$ (28)	$ (20)

Segment Information (Disaggrega

Segment Information (Disaggregation of Revenue) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Disaggregation of Revenue [Line Items]
Revenues	$ 2,062	$ 1,879
Revenues	2,062	1,879
Revenues from alternative revenue programs	98	45
Other revenues not from contracts with customers	(3)	3
Union Electric Company
Disaggregation of Revenue [Line Items]
Revenues from alternative revenue programs	(2)	(6)
Other revenues not from contracts with customers	(6)	0
Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues from alternative revenue programs	64	55
Other revenues not from contracts with customers	2	2
Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues from alternative revenue programs	28	(5)
Other revenues not from contracts with customers	1	1
Ameren Transmission
Disaggregation of Revenue [Line Items]
Revenues from alternative revenue programs	8	1
Other revenues not from contracts with customers	0	0
Electric
Disaggregation of Revenue [Line Items]
Revenues	1,590	1,318
Revenues	1,590	1,318
Electric | Residential
Disaggregation of Revenue [Line Items]
Revenues	706	595
Electric | Commercial
Disaggregation of Revenue [Line Items]
Revenues	447	398
Electric | Industrial
Disaggregation of Revenue [Line Items]
Revenues	109	102
Electric | Other
Disaggregation of Revenue [Line Items]
Revenues	328	223
Natural gas
Disaggregation of Revenue [Line Items]
Revenues	472	561
Revenues	472	561
Natural gas | Residential
Disaggregation of Revenue [Line Items]
Revenues	348	420
Natural gas | Commercial
Disaggregation of Revenue [Line Items]
Revenues	100	119
Natural gas | Industrial
Disaggregation of Revenue [Line Items]
Revenues	9	19
Natural gas | Other
Disaggregation of Revenue [Line Items]
Revenues	15	3
Ameren Illinois Company
Disaggregation of Revenue [Line Items]
Revenues	1,101	1,024
Revenues	1,101	1,024
Revenues from alternative revenue programs	99	51
Other revenues not from contracts with customers	3	3
Ameren Illinois Company | Residential
Disaggregation of Revenue [Line Items]
Revenues	678	632
Ameren Illinois Company | Commercial
Disaggregation of Revenue [Line Items]
Revenues	277	255
Ameren Illinois Company | Industrial
Disaggregation of Revenue [Line Items]
Revenues	55	62
Ameren Illinois Company | Other
Disaggregation of Revenue [Line Items]
Revenues	91	75
Ameren Illinois Company | Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues from alternative revenue programs	64	55
Other revenues not from contracts with customers	2	2
Ameren Illinois Company | Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues from alternative revenue programs	28	(5)
Other revenues not from contracts with customers	1	1
Ameren Illinois Company | Ameren Illinois Transmission
Disaggregation of Revenue [Line Items]
Revenues from alternative revenue programs	7	1
Other revenues not from contracts with customers	0	0
Ameren Illinois Company | Electric
Disaggregation of Revenue [Line Items]
Revenues	710	543
Ameren Illinois Company | Natural gas
Disaggregation of Revenue [Line Items]
Revenues	391	481
Operating Segments | Union Electric Company
Disaggregation of Revenue [Line Items]
Revenues	913	808
Revenues	923	818
Operating Segments | Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues	624	464
Revenues	624	465
Operating Segments | Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues	391	481
Revenues	391	481
Operating Segments | Ameren Transmission
Disaggregation of Revenue [Line Items]
Revenues	134	126
Revenues	163	146
Operating Segments | Electric | Union Electric Company
Disaggregation of Revenue [Line Items]
Revenues	841	738
Operating Segments | Electric | Union Electric Company | Residential
Disaggregation of Revenue [Line Items]
Revenues	324	332
Operating Segments | Electric | Union Electric Company | Commercial
Disaggregation of Revenue [Line Items]
Revenues	247	240
Operating Segments | Electric | Union Electric Company | Industrial
Disaggregation of Revenue [Line Items]
Revenues	61	57
Operating Segments | Electric | Union Electric Company | Other
Disaggregation of Revenue [Line Items]
Revenues	209	109
Operating Segments | Electric | Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues	624	465
Operating Segments | Electric | Ameren Illinois Electric Distribution | Residential
Disaggregation of Revenue [Line Items]
Revenues	382	263
Operating Segments | Electric | Ameren Illinois Electric Distribution | Commercial
Disaggregation of Revenue [Line Items]
Revenues	200	158
Operating Segments | Electric | Ameren Illinois Electric Distribution | Industrial
Disaggregation of Revenue [Line Items]
Revenues	48	45
Operating Segments | Electric | Ameren Illinois Electric Distribution | Other
Disaggregation of Revenue [Line Items]
Revenues	(6)	(1)
Operating Segments | Electric | Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues	0	0
Operating Segments | Electric | Ameren Illinois Natural Gas | Residential
Disaggregation of Revenue [Line Items]
Revenues	0	0
Operating Segments | Electric | Ameren Illinois Natural Gas | Commercial
Disaggregation of Revenue [Line Items]
Revenues	0	0
Operating Segments | Electric | Ameren Illinois Natural Gas | Industrial
Disaggregation of Revenue [Line Items]
Revenues	0	0
Operating Segments | Electric | Ameren Illinois Natural Gas | Other
Disaggregation of Revenue [Line Items]
Revenues	0	0
Operating Segments | Electric | Ameren Transmission
Disaggregation of Revenue [Line Items]
Revenues	163	146
Operating Segments | Electric | Ameren Transmission | Residential
Disaggregation of Revenue [Line Items]
Revenues	0	0
Operating Segments | Electric | Ameren Transmission | Commercial
Disaggregation of Revenue [Line Items]
Revenues	0	0
Operating Segments | Electric | Ameren Transmission | Industrial
Disaggregation of Revenue [Line Items]
Revenues	0	0
Operating Segments | Electric | Ameren Transmission | Other
Disaggregation of Revenue [Line Items]
Revenues	163	146
Operating Segments | Natural gas | Union Electric Company
Disaggregation of Revenue [Line Items]
Revenues	82	80
Operating Segments | Natural gas | Union Electric Company | Residential
Disaggregation of Revenue [Line Items]
Revenues	52	51
Operating Segments | Natural gas | Union Electric Company | Commercial
Disaggregation of Revenue [Line Items]
Revenues	23	22
Operating Segments | Natural gas | Union Electric Company | Industrial
Disaggregation of Revenue [Line Items]
Revenues	2	2
Operating Segments | Natural gas | Union Electric Company | Other
Disaggregation of Revenue [Line Items]
Revenues	5	5
Operating Segments | Natural gas | Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues	0	0
Operating Segments | Natural gas | Ameren Illinois Electric Distribution | Residential
Disaggregation of Revenue [Line Items]
Revenues	0	0
Operating Segments | Natural gas | Ameren Illinois Electric Distribution | Commercial
Disaggregation of Revenue [Line Items]
Revenues	0	0
Operating Segments | Natural gas | Ameren Illinois Electric Distribution | Industrial
Disaggregation of Revenue [Line Items]
Revenues	0	0
Operating Segments | Natural gas | Ameren Illinois Electric Distribution | Other
Disaggregation of Revenue [Line Items]
Revenues	0	0
Operating Segments | Natural gas | Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues	391	481
Operating Segments | Natural gas | Ameren Illinois Natural Gas | Residential
Disaggregation of Revenue [Line Items]
Revenues	296	369
Operating Segments | Natural gas | Ameren Illinois Natural Gas | Commercial
Disaggregation of Revenue [Line Items]
Revenues	77	97
Operating Segments | Natural gas | Ameren Illinois Natural Gas | Industrial
Disaggregation of Revenue [Line Items]
Revenues	7	17
Operating Segments | Natural gas | Ameren Illinois Natural Gas | Other
Disaggregation of Revenue [Line Items]
Revenues	11	(2)
Operating Segments | Natural gas | Ameren Transmission
Disaggregation of Revenue [Line Items]
Revenues	0	0
Operating Segments | Natural gas | Ameren Transmission | Residential
Disaggregation of Revenue [Line Items]
Revenues	0	0
Operating Segments | Natural gas | Ameren Transmission | Commercial
Disaggregation of Revenue [Line Items]
Revenues	0	0
Operating Segments | Natural gas | Ameren Transmission | Industrial
Disaggregation of Revenue [Line Items]
Revenues	0	0
Operating Segments | Natural gas | Ameren Transmission | Other
Disaggregation of Revenue [Line Items]
Revenues	0	0
Operating Segments | Ameren Illinois Company | Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues	624	465
Operating Segments | Ameren Illinois Company | Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues	391	481
Operating Segments | Ameren Illinois Company | Ameren Illinois Transmission
Disaggregation of Revenue [Line Items]
Revenues	86	78
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues	624	465
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Electric Distribution | Residential
Disaggregation of Revenue [Line Items]
Revenues	382	263
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Electric Distribution | Commercial
Disaggregation of Revenue [Line Items]
Revenues	200	158
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Electric Distribution | Industrial
Disaggregation of Revenue [Line Items]
Revenues	48	45
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Electric Distribution | Other
Disaggregation of Revenue [Line Items]
Revenues	(6)	(1)
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Transmission
Disaggregation of Revenue [Line Items]
Revenues	114	98
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Transmission | Residential
Disaggregation of Revenue [Line Items]
Revenues	0	0
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Transmission | Commercial
Disaggregation of Revenue [Line Items]
Revenues	0	0
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Transmission | Industrial
Disaggregation of Revenue [Line Items]
Revenues	0	0
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Transmission | Other
Disaggregation of Revenue [Line Items]
Revenues	114	98
Operating Segments | Ameren Illinois Company | Natural gas | Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues	391	481
Operating Segments | Ameren Illinois Company | Natural gas | Ameren Illinois Natural Gas | Residential
Disaggregation of Revenue [Line Items]
Revenues	296	369
Operating Segments | Ameren Illinois Company | Natural gas | Ameren Illinois Natural Gas | Commercial
Disaggregation of Revenue [Line Items]
Revenues	77	97
Operating Segments | Ameren Illinois Company | Natural gas | Ameren Illinois Natural Gas | Industrial
Disaggregation of Revenue [Line Items]
Revenues	7	17
Operating Segments | Ameren Illinois Company | Natural gas | Ameren Illinois Natural Gas | Other
Disaggregation of Revenue [Line Items]
Revenues	11	(2)
Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Revenues	(39)	(31)
Revenues	(39)	(31)
Intersegment Eliminations | Union Electric Company
Disaggregation of Revenue [Line Items]
Revenues	(10)	(10)
Intersegment Eliminations | Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues	0	(1)
Intersegment Eliminations | Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues	0	0
Intersegment Eliminations | Ameren Transmission
Disaggregation of Revenue [Line Items]
Revenues	(29)	(20)
Intersegment Eliminations | Electric
Disaggregation of Revenue [Line Items]
Revenues	(38)	(31)
Intersegment Eliminations | Electric | Residential
Disaggregation of Revenue [Line Items]
Revenues	0	0
Intersegment Eliminations | Electric | Commercial
Disaggregation of Revenue [Line Items]
Revenues	0	0
Intersegment Eliminations | Electric | Industrial
Disaggregation of Revenue [Line Items]
Revenues	0	0
Intersegment Eliminations | Electric | Other
Disaggregation of Revenue [Line Items]
Revenues	(38)	(31)
Intersegment Eliminations | Natural gas
Disaggregation of Revenue [Line Items]
Revenues	(1)	0
Intersegment Eliminations | Natural gas | Residential
Disaggregation of Revenue [Line Items]
Revenues	0	0
Intersegment Eliminations | Natural gas | Commercial
Disaggregation of Revenue [Line Items]
Revenues	0	0
Intersegment Eliminations | Natural gas | Industrial
Disaggregation of Revenue [Line Items]
Revenues	0	0
Intersegment Eliminations | Natural gas | Other
Disaggregation of Revenue [Line Items]
Revenues	(1)	0
Intersegment Eliminations | Ameren Illinois Company
Disaggregation of Revenue [Line Items]
Revenues	(28)	(20)
Revenues	(28)	(20)
Intersegment Eliminations | Ameren Illinois Company | Residential
Disaggregation of Revenue [Line Items]
Revenues	0	0
Intersegment Eliminations | Ameren Illinois Company | Commercial
Disaggregation of Revenue [Line Items]
Revenues	0	0
Intersegment Eliminations | Ameren Illinois Company | Industrial
Disaggregation of Revenue [Line Items]
Revenues	0	0
Intersegment Eliminations | Ameren Illinois Company | Other
Disaggregation of Revenue [Line Items]
Revenues	(28)	(20)
Intersegment Eliminations | Ameren Illinois Company | Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues	0	0
Intersegment Eliminations | Ameren Illinois Company | Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues	0	0
Intersegment Eliminations | Ameren Illinois Company | Ameren Illinois Transmission
Disaggregation of Revenue [Line Items]
Revenues	$ (28)	$ (20)