Cover Page - shares	6 Months Ended
Cover Page - shares	Jun. 30, 2024	Jul. 31, 2024
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2024
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		266,816,725
Entity Central Index Key	0001002910
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q2
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	2024
Document Fiscal Period Focus	Q2
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	2024
Document Fiscal Period Focus	Q2
Amendment Flag	false

Consolidated Statement of Income (Loss) and Comprehensive Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Operating Revenues:
Total operating revenues	$ 1,693	$ 1,760	$ 3,509	$ 3,822
Operating Expenses:
Fuel and purchased power	327	480	655	1,088
Natural gas purchased for resale	33	42	184	250
Other operations and maintenance	465	450	935	898
Depreciation and amortization	376	335	737	655
Taxes other than income taxes	131	124	266	251
Total operating expenses	1,332	1,431	2,777	3,142
Operating Income	361	329	732	680
Other Income, Net	103	82	192	160
Interest Charges	165	134	319	261
Income Before Income Taxes	299	277	605	579
Income Taxes	39	38	83	75
Net Income	260	239	522	504
Less: Net Income Attributable to Noncontrolling Interests	2	2	3	3
Net Income Attributable to Ameren Common Shareholders	258	237	519	501
Pension and other postretirement benefit plan activity, net of income taxes (benefit)	(2)	(1)	(3)	(2)
Comprehensive Income	258	238	519	502
Less: Comprehensive Income Attributable to Noncontrolling Interests	2	2	3	3
Comprehensive Income Attributable to Ameren Common Shareholders	$ 256	$ 236	$ 516	$ 499
Earnings Per Share, Basic [Abstract]
Earnings per Common Share – Basic	$ 0.97	$ 0.90	$ 1.95	$ 1.91
Earnings Per Share, Diluted [Abstract]
Earnings per Common Share – Diluted	$ 0.97	$ 0.90	$ 1.95	$ 1.90
Weighted-average Common Shares Outstanding – Basic	266.7	262.6	266.5	262.4
Weighted-average Common Shares Outstanding – Diluted	266.8	263.2	266.8	263.2
Electric
Operating Revenues:
Total operating revenues	$ 1,521	$ 1,585	$ 2,885	$ 3,175
Natural gas
Operating Revenues:
Total operating revenues	172	175	624	647
Union Electric Company
Operating Revenues:
Total operating revenues	888	941	1,663	1,864
Operating Expenses:
Fuel and purchased power	189	289	355	610
Natural gas purchased for resale	9	9	37	56
Other operations and maintenance	247	237	501	476
Depreciation and amortization	208	186	403	362
Taxes other than income taxes	91	88	178	168
Total operating expenses	744	809	1,474	1,672
Operating Income	144	132	189	192
Other Income, Net	49	22	93	41
Interest Charges	63	52	125	103
Income Before Income Taxes	130	102	157	130
Income Taxes	1	(1)	2	(2)
Net Income	129	103	155	132
Preferred Stock Dividends	1	1	2	2
Net Income Attributable to Parent	128	102	153	130
Union Electric Company \| Electric
Operating Revenues:
Total operating revenues	864	918	1,578	1,759
Union Electric Company \| Natural gas
Operating Revenues:
Total operating revenues	24	23	85	105
Ameren Illinois Company
Operating Revenues:
Total operating revenues	766	779	1,766	1,880
Operating Expenses:
Purchased Power	141	192	305	479
Natural gas purchased for resale	24	33	147	194
Other operations and maintenance	224	201	434	403
Depreciation and amortization	154	138	307	271
Taxes other than income taxes	35	32	79	74
Total operating expenses	578	596	1,272	1,421
Operating Income	188	183	494	459
Other Income, Net	37	41	68	78
Interest Charges	60	50	115	97
Income Before Income Taxes	165	174	447	440
Income Taxes	40	44	107	112
Net Income	125	130	340	328
Preferred Stock Dividends	1	1	1	1
Net Income Attributable to Parent	124	129	339	327
Ameren Illinois Company \| Electric
Operating Revenues:
Total operating revenues	618	627	1,227	1,337
Ameren Illinois Company \| Natural gas
Operating Revenues:
Total operating revenues	$ 148	$ 152	$ 539	$ 543

Consolidated Statement of Income (Loss) and Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Income Statement [Abstract]
Pension and other postretirement benefit plan activity, tax	$ (1)	$ 0	$ (1)	$ 0

Consolidated Balance Sheet - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Current Assets:
Cash and cash equivalents	$ 19	$ 25
Accounts receivable - trade (less allowance for doubtful accounts)	514	494
Unbilled revenue	407	319
Miscellaneous accounts receivable	62	106
Inventories	740	733
Current regulatory assets	345	365
Other current assets	130	139
Total current assets	2,217	2,181
Property, Plant, and Equipment, Net	34,873	33,776
Investments and Other Assets:
Nuclear decommissioning trust fund	1,266	1,150
Goodwill	411	411
Regulatory assets	1,952	1,810
Pension and other postretirement benefits	566	581
Other assets	1,049	921
Total investments and other assets	5,244	4,873
TOTAL ASSETS	42,334	40,830
Current Liabilities:
Current maturities of long-term debt	799	849
Short-term debt	691	536
Accounts and wages payable	774	1,136
Interest accrued	177	147
Customer deposits	197	176
Other current liabilities	655	501
Total current liabilities	3,293	3,345
Long-term Debt, Net	16,280	15,121
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes and tax credits, net	4,325	4,176
Regulatory liabilities	5,531	5,512
Asset retirement obligations	791	772
Other deferred credits and liabilities	446	426
Total deferred credits and other liabilities	11,093	10,886
Commitments and Contingencies
Shareholders’ Equity:
Common Stock	3	3
Other paid-in capital, principally premium on common stock	7,246	7,216
Retained earnings	4,299	4,136
Accumulated other comprehensive loss	(9)	(6)
Total shareholders’ equity	11,539	11,349
Noncontrolling Interests	129	129
Total equity	11,668	11,478
TOTAL LIABILITIES AND EQUITY	42,334	40,830
Union Electric Company
Current Assets:
Cash and cash equivalents	0	0
Unbilled revenue	271	163
Miscellaneous accounts receivable	30	26
Inventories	520	508
Current regulatory assets	124	101
Other current assets	63	68
Total current assets	1,286	1,142
Property, Plant, and Equipment, Net	17,938	17,250
Investments and Other Assets:
Nuclear decommissioning trust fund	1,266	1,150
Regulatory assets	733	755
Pension and other postretirement benefits	138	157
Other assets	194	152
Total investments and other assets	2,331	2,214
TOTAL ASSETS	21,555	20,606
Current Liabilities:
Current maturities of long-term debt	0	350
Short-term debt	390	170
Borrowings from money pool	0	306
Interest accrued	82	69
Taxes accrued	132	28
Other current liabilities	234	153
Total current liabilities	1,262	1,747
Long-term Debt, Net	6,830	5,991
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes and tax credits, net	2,196	2,122
Regulatory liabilities	2,925	2,959
Asset retirement obligations	788	768
Other deferred credits and liabilities	88	56
Total deferred credits and other liabilities	5,997	5,905
Commitments and Contingencies
Shareholders’ Equity:
Common Stock	511	511
Other paid-in capital, principally premium on common stock	3,075	2,725
Preferred stock	80	80
Retained earnings	3,800	3,647
Total shareholders’ equity	7,466	6,963
TOTAL LIABILITIES AND EQUITY	21,555	20,606
Union Electric Company \| Nonrelated Party
Current Assets:
Accounts receivable - trade (less allowance for doubtful accounts)	211	204
Current Liabilities:
Accounts and wages payable	366	618
Union Electric Company \| Related Party
Current Assets:
Accounts receivable - trade (less allowance for doubtful accounts)	67	72
Current Liabilities:
Accounts and wages payable	58	53
Ameren Illinois Company
Current Assets:
Cash and cash equivalents	6	0
Advances to money pool	30	0
Unbilled revenue	136	156
Miscellaneous accounts receivable	5	44
Inventories	216	225
Current regulatory assets	215	252
Other current assets	55	62
Total current assets	961	1,047
Property, Plant, and Equipment, Net	15,009	14,632
Investments and Other Assets:
Goodwill	411	411
Regulatory assets	1,189	1,035
Pension and other postretirement benefits	412	394
Other assets	656	603
Total investments and other assets	2,668	2,443
TOTAL ASSETS	18,638	18,122
Current Liabilities:
Current maturities of long-term debt	300	0
Short-term debt	0	366
Borrowings from money pool	0	135
Customer deposits	161	141
Zero emission credit liabilities	64	35
Current regulatory liabilities	58	71
Other current liabilities	219	263
Total current liabilities	1,196	1,433
Long-term Debt, Net	5,551	5,232
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes and tax credits, net	1,967	1,906
Regulatory liabilities	2,466	2,418
Other deferred credits and liabilities	319	308
Total deferred credits and other liabilities	4,752	4,632
Commitments and Contingencies
Shareholders’ Equity:
Common Stock	0	0
Other paid-in capital, principally premium on common stock	3,020	3,020
Preferred stock	49	49
Retained earnings	4,070	3,756
Total shareholders’ equity	7,139	6,825
TOTAL LIABILITIES AND EQUITY	18,638	18,122
Ameren Illinois Company \| Nonrelated Party
Current Assets:
Accounts receivable - trade (less allowance for doubtful accounts)	287	273
Current Liabilities:
Accounts and wages payable	297	370
Ameren Illinois Company \| Related Party
Current Assets:
Accounts receivable - trade (less allowance for doubtful accounts)	11	35
Current Liabilities:
Accounts and wages payable	$ 97	$ 52

Consolidated Balance Sheet (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Accounts Receivable, Allowance for Credit Loss, Current	$ 37	$ 30
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	400,000,000.0	400,000,000.0
Common Stock, Shares, Outstanding	266,800,000	266,300,000
Union Electric Company
Accounts Receivable, Allowance for Credit Loss, Current	$ 12	$ 12
Common stock, par value (in dollars per share)	$ 5	$ 5
Common stock, shares authorized (in shares)	150,000,000.0	150,000,000.0
Common Stock, Shares, Outstanding	102,100,000	102,100,000
Ameren Illinois Company
Accounts Receivable, Allowance for Credit Loss, Current	$ 25	$ 18
Common stock, no par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized (in shares)	45,000,000.0	45,000,000.0
Common Stock, Shares, Outstanding	25,500,000	25,500,000

Consolidated Statement of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Cash Flows From Operating Activities:
Net income	$ 522	$ 504
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	760	703
Amortization of nuclear fuel	38	36
Amortization of debt issuance costs and premium/discounts	9	8
Deferred income taxes and investment tax credits, net	76	66
Allowance for equity funds used during construction	(25)	(23)
Stock-based compensation costs	14	14
Other	13	(19)
Changes in assets and liabilities:
Receivables	(85)	173
Inventories	(7)	(44)
Accounts and wages payable	(210)	(335)
Taxes accrued	121	93
Regulatory assets and liabilities	(105)	(81)
Assets, other	(53)	(38)
Liabilities, other	100	34
Pension and other postretirement benefits	(112)	(114)
Counterparty collateral, net	(7)	134
Net cash provided by operating activities	1,049	1,111
Cash Flows From Investing Activities:
Capital expenditures	(1,892)	(1,822)
Nuclear fuel expenditures	(37)	(50)
Purchases of securities – nuclear decommissioning trust fund	(323)	(81)
Sales and maturities of securities – nuclear decommissioning trust fund	309	65
Other	11	(1)
Net cash used in investing activities	(1,932)	(1,889)
Cash Flows From Financing Activities:
Dividends on common stock	(356)	(330)
Dividends paid to noncontrolling interest holders	(3)	(3)
Short-term debt, net	156	260
Maturities of long-term debt	(350)	(100)
Issuances of long-term debt	1,470	997
Issuances of common stock	21	16
Employee payroll taxes related to stock-based compensation	(8)	(20)
Debt issuance costs	(18)	(9)
Other	0	(3)
Net cash provided by financing activities	912	808
Net change in cash, cash equivalents, and restricted cash	29	30
Cash, cash equivalents, and restricted cash at beginning of year	272	216
Cash, cash equivalents, and restricted cash at end of period	301	246
Union Electric Company
Cash Flows From Operating Activities:
Net income	155	132
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	426	410
Amortization of nuclear fuel	38	36
Amortization of debt issuance costs and premium/discounts	3	3
Deferred income taxes and investment tax credits, net	38	10
Allowance for equity funds used during construction	(23)	(12)
Other	22	(20)
Changes in assets and liabilities:
Receivables	(121)	(9)
Inventories	(12)	(81)
Accounts and wages payable	(196)	(231)
Taxes accrued	118	103
Regulatory assets and liabilities	(31)	28
Assets, other	(30)	13
Liabilities, other	63	21
Pension and other postretirement benefits	(40)	(41)
Counterparty collateral, net	(3)	81
Net cash provided by operating activities	407	443
Cash Flows From Investing Activities:
Capital expenditures	(1,104)	(914)
Nuclear fuel expenditures	(37)	(50)
Purchases of securities – nuclear decommissioning trust fund	(323)	(81)
Sales and maturities of securities – nuclear decommissioning trust fund	309	65
Net cash used in investing activities	(1,155)	(980)
Cash Flows From Financing Activities:
Dividends on preferred stock	(2)	(2)
Short-term debt, net	220	44
Money pool borrowings, net	(306)	0
Maturities of long-term debt	(350)	0
Issuances of long-term debt	846	499
Capital contributions from parent	350	0
Debt issuance costs	(9)	(6)
Other	0	(3)
Net cash provided by financing activities	749	532
Net change in cash, cash equivalents, and restricted cash	1	(5)
Cash, cash equivalents, and restricted cash at beginning of year	10	13
Cash, cash equivalents, and restricted cash at end of period	11	8
Ameren Illinois Company
Cash Flows From Operating Activities:
Net income	340	328
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	307	271
Amortization of debt issuance costs and premium/discounts	2	2
Deferred income taxes and investment tax credits, net	37	70
Allowance for equity funds used during construction	(2)	(10)
Other	8	12
Changes in assets and liabilities:
Receivables	27	182
Inventories	9	37
Accounts and wages payable	7	(92)
Taxes accrued	55	(36)
Regulatory assets and liabilities	(70)	(105)
Assets, other	(23)	(42)
Liabilities, other	32	13
Pension and other postretirement benefits	(43)	(46)
Counterparty collateral, net	5	53
Net cash provided by operating activities	691	637
Cash Flows From Investing Activities:
Capital expenditures	(717)	(844)
Money pool advances, net	(30)	0
Other	5	(2)
Net cash used in investing activities	(742)	(846)
Cash Flows From Financing Activities:
Dividends on common stock	(25)	0
Dividends on preferred stock	(1)	(1)
Short-term debt, net	(366)	(147)
Money pool borrowings, net	(135)	0
Maturities of long-term debt	0	(100)
Issuances of long-term debt	624	498
Debt issuance costs	(7)	(3)
Net cash provided by financing activities	90	247
Net change in cash, cash equivalents, and restricted cash	39	38
Cash, cash equivalents, and restricted cash at beginning of year	234	191
Cash, cash equivalents, and restricted cash at end of period	$ 273	$ 229

Consolidated Statement of Stockholders' Equity - USD ($) $ in Millions	Total	Common Stock	Other Paid-in Capital:	Retained Earnings:	Deferred Retirement Benefit Costs	Accumulated Other Comprehensive Loss:	Total 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 period at Dec. 31, 2022			$ 6,860	$ 3,646	$ (1)			$ 129			$ 2,725		$ 3,111					$ 3,190
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under the DRPlus and 401(k) plan			23
Stock-based compensation activity			(3)
Net income	$ 504								$ 132				132	$ 328				328
Net income attributable to Ameren common shareholders	501			501
Dividends on common stock				(330)														0
Preferred stock dividends													(2)					(1)
Change in deferred retirement benefit costs	(2)				(2)
Net income attributable to noncontrolling interest holders	$ (3)							3
Dividends paid to noncontrolling interest holders								(3)
Common stock shares outstanding at beginning of period at Dec. 31, 2022	262,000,000.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under the DRPlus and 401(k) plan	200,000
Shares issued for stock-based compensation	500,000
Common stock shares outstanding at end of period at Jun. 30, 2023	262,700,000
End of period at Jun. 30, 2023	$ 10,826	$ 3	6,880	3,817	(3)	$ (3)		129		$ 511	2,725	$ 80	3,241		$ 0	$ 2,929	$ 49	3,517
Shareholders' equity, end of year at Jun. 30, 2023							$ 10,697		6,557					6,495
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per common share	$ 1.26
Beginning of period at Mar. 31, 2023			6,861	3,745	(2)			129			2,725		3,139					3,388
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under the DRPlus and 401(k) plan			11
Stock-based compensation activity			8
Net income	$ 239								103				103	130				130
Net income attributable to Ameren common shareholders	237			237
Dividends on common stock				(165)														0
Preferred stock dividends													(1)					(1)
Change in deferred retirement benefit costs	(1)				(1)
Net income attributable to noncontrolling interest holders	$ (2)							2
Dividends paid to noncontrolling interest holders								(2)
Common stock shares outstanding at beginning of period at Mar. 31, 2023	262,600,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under the DRPlus and 401(k) plan	100,000
Shares issued for stock-based compensation	0
Common stock shares outstanding at end of period at Jun. 30, 2023	262,700,000
End of period at Jun. 30, 2023	$ 10,826	3	6,880	3,817	(3)	(3)		129		511	2,725	80	3,241		0	2,929	49	3,517
Shareholders' equity, end of year at Jun. 30, 2023							10,697		$ 6,557					$ 6,495
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per common share	$ 0.63
Beginning of period at Dec. 31, 2023	$ 11,478		7,216	4,136	(6)			129			2,725		3,647					3,756
Common stock shares outstanding at beginning of period at Dec. 31, 2023	266,300,000								102,100,000					25,500,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued for stock-based compensation	200,000
Common stock shares outstanding at end of period at Mar. 31, 2024	266,600,000
End of period at Mar. 31, 2024			7,228	4,219	(7)			129			2,725		3,672					3,971
Beginning of period at Dec. 31, 2023	$ 11,478		7,216	4,136	(6)			129			2,725		3,647					3,756
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under the DRPlus and 401(k) plan			21
Stock-based compensation activity			9
Net income	522								$ 155				155	$ 340				340
Net income attributable to Ameren common shareholders	519			519
Dividends on common stock				(356)														(25)
Preferred stock dividends													(2)					(1)
Change in deferred retirement benefit costs	(3)				(3)
Net income attributable to noncontrolling interest holders	$ (3)							3
Dividends paid to noncontrolling interest holders								(3)
Common stock shares outstanding at beginning of period at Dec. 31, 2023	266,300,000								102,100,000					25,500,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under the DRPlus and 401(k) plan	300,000
Shares issued for stock-based compensation	200,000
Common stock shares outstanding at end of period at Jun. 30, 2024	266,800,000								102,100,000					25,500,000
End of period at Jun. 30, 2024	$ 11,668	3	7,246	4,299	(9)	(9)		129		511	3,075	80	3,800		0	3,020	49	4,070
Shareholders' equity, end of year at Jun. 30, 2024	$ 11,539						11,539		$ 7,466					$ 7,139
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per common share	$ 1.34
Beginning of period at Mar. 31, 2024			7,228	4,219	(7)			129			2,725		3,672					3,971
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under the DRPlus and 401(k) plan			11
Stock-based compensation activity			7
Net income	$ 260								$ 129				129	$ 125				125
Net income attributable to Ameren common shareholders	258			258
Dividends on common stock				(178)														(25)
Preferred stock dividends													(1)					(1)
Change in deferred retirement benefit costs	(2)				(2)
Net income attributable to noncontrolling interest holders	$ (2)							2
Dividends paid to noncontrolling interest holders								(2)
Common stock shares outstanding at beginning of period at Mar. 31, 2024	266,600,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under the DRPlus and 401(k) plan	200,000
Shares issued for stock-based compensation	0
Common stock shares outstanding at end of period at Jun. 30, 2024	266,800,000								102,100,000					25,500,000
End of period at Jun. 30, 2024	$ 11,668	$ 3	$ 7,246	$ 4,299	$ (9)	$ (9)		$ 129		$ 511	$ 3,075	$ 80	$ 3,800		$ 0	$ 3,020	$ 49	$ 4,070
Shareholders' equity, end of year at Jun. 30, 2024	$ 11,539						$ 11,539		$ 7,466					$ 7,139
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per common share	$ 0.67

Summary Of Significant Accounting Policies	6 Months Ended
Summary Of Significant Accounting Policies	Jun. 30, 2024
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 also 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 statement of our results. The preparation of financial statements in conformity with GAAP requires management to make certain estimates and assumptions. Such estimates and assumptions affect reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the dates of financial statements, and the reported amounts of revenues and expenses during the 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 June 30, 2024, and December 31, 2023, Ameren had unconsolidated variable interests in various equity method investments, primarily to advance clean and resilient energy technologies, totaling $75 million and $73 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 June 30, 2024, Ameren’s maximum exposure to loss related to these variable interests is limited to its investment of $75 million plus associated outstanding funding commitments of $12 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 June 30, 2024, the cash surrender value of COLI at Ameren and Ameren Illinois was $255 million (December 31, 2023 – $248 million) and $114 million (December 31, 2023 – $111 million), respectively, while total borrowings against the policies were $103 million (December 31, 2023 – $104 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

6 Months Ended

Jun. 30, 2024

Public Utilities, General Disclosures [Abstract]

RATE AND REGULATORY MATTERS

Below 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

2024 Electric Service Regulatory Rate Review

In June 2024, Ameren Missouri filed a request with the MoPSC seeking approval to increase its annual revenues for electric service by $446 million. The electric rate increase request is based on a 10.25% return on common equity, a capital structure composed of 52% common equity, a rate base of $14 billion, and a test year ended March 31, 2024, with certain pro-forma adjustments expected through an anticipated true-up date of December 31, 2024. Ameren Missouri also requested the continued use of the FAC and trackers for pension and postretirement benefits, uncertain income tax positions, certain excess deferred income taxes, and the utilization of production and investment tax credits or proceeds from the sale of tax credits allowed under the IRA, which the MoPSC previously authorized in earlier electric rate orders. The electric rate increase request reflects the following:

•increased infrastructure investments made under Ameren Missouri’s Smart Energy Plan, including increased cost of capital and depreciation expense. Included in these investments are 500 megawatts of solar generation investment for the Boomtown, Cass County and Huck Finn solar projects along with investments in the Callaway nuclear energy center and other dispatchable generation to support a reliable, low-cost and cleaner mix of energy resources;

•decreased costs resulting from the planned retirement of the Rush Island Energy Center; and

•decreased costs related to the extension of the retirement date of the Sioux Energy Center from 2030 to 2032, consistent with Ameren Missouri’s integrated resource plan filed with the MoPSC in September 2023, to ensure reliability.

The MoPSC proceeding relating to the proposed electric service rate changes will take place over a period of up to 11 months, with a decision by the MoPSC expected by May 2025 and new rates effective by June 2025. Ameren Missouri cannot predict the level of any electric service rate change the MoPSC may approve, whether the requested regulatory recovery mechanisms will be continued, 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.

Generation Facilities

During 2022 and 2023, Ameren Missouri, and certain subsidiaries of Ameren Missouri, entered into agreements to acquire and/or construct various generation facilities. The solar generation facilities are eligible for recovery under the PISA. The following table provides information with respect to each agreement:

Agreement type

Facility size

Status of MoPSC CCN

Status of FERC approval of acquisition

Anticipated in-service date(a)

Huck Finn Solar Project(b)(c)

Build-transfer

200-MW

Approved February 2023

Received March 2023

Fourth quarter 2024

Boomtown Solar Project(c)(d)

Build-transfer

150-MW

Approved April 2023

Received October 2023

Fourth quarter 2024(e)

Cass County Solar Project(d)

Development-transfer(f)

150-MW

Approved June 2024

Not applicable

Fourth quarter 2024

Vandalia Solar Project(c)(g)

Self-build

50-MW

Approved March 2024

Not applicable

Fourth quarter 2025

Bowling Green Solar Project(c)(g)

Self-build

50-MW

Approved March 2024

Not applicable

First quarter 2026

Split Rail Solar Project(g)

Build-transfer

300-MW

Approved March 2024

Requested July 2024

Mid-2026

Castle Bluff Natural Gas Project

Self-build

800-MW

Filed June 2024

Not applicable

Fourth quarter 2027

(a)Anticipated in-service dates are dependent on the timing of regulatory approvals and construction completion, among other things.

(b)The Huck Finn Solar Project is expected to support Ameren Missouri’s compliance with the state of Missouri’s renewable energy standard. Investments in the project will be eligible for recovery under the RESRAM. Ameren Missouri expects to close on the acquisition of the Huck Finn Solar Project in the fourth quarter of 2024.

(c)These projects collectively represent approximately $0.85 billion of expected capital expenditures.

(d)The Boomtown and Cass County solar projects are expected to support Ameren Missouri’s transition to renewable energy generation and serve customers under the Renewable Solutions Program.

(e)Ameren Missouri expects to close on the acquisition of the Boomtown Solar Project in August 2024.

(f)In June 2024, Ameren Missouri acquired the Cass County Solar Project, which includes solar panels, project design, land rights, and engineering, procurement, and construction agreements, for approximately $250 million and took over construction management of the project.

(g)These solar projects are expected to support Ameren Missouri’s transition to renewable energy generation.

Securitization of Rush Island Energy Center Costs

In June 2024, the MoPSC issued a financing order authorizing the issuance of securitized utility tariff bonds by a wholly owned, special purpose subsidiary of Ameren Missouri to finance approximately $470 million of costs related to the planned accelerated retirement of the Rush Island Energy Center, which includes the expected remaining unrecovered net plant balance associated with the facility, among other costs. Ameren Missouri initially petitioned the MoPSC in November 2023 to finance $519 million of costs. The difference between the initial petition and final financing order will be considered for recovery in future rate proceedings involving the securitized utility tariff charge or base rates. Ameren Missouri will collect the amounts necessary to repay the bonds over approximately 15 years from the date of bond issuance. The financing order also includes a determination that the decision to retire the Rush Island Energy Center was reasonable and prudent. The MoPSC did not make a determination regarding the prudency of Ameren Missouri's prior actions that resulted in the adverse ruling in the NSR and Clean Air Act litigation discussed in Note 9 – Commitments and Contingencies. However, claims regarding such actions could be considered in future regulatory proceedings. If future regulatory proceedings result in revenue reductions based on Ameren Missouri’s prior actions that resulted in the adverse ruling in the NSR and Clean Air Act litigation, it could have a material adverse effect on the results of operations, financial position, and liquidity of Ameren and Ameren Missouri. In July 2024, the MoOPC filed a request for rehearing of the financing order. Ameren Missouri expects a decision on the rehearing request in August 2024. The decision on the rehearing request is subject to appeal. The timing of the issuance of securitized utility tariff bonds is dependent on the conclusion of any appeal process.

MEEIA

In January 2024, 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 customers its actual MEEIA program costs and related lost electric revenues. If the plan is approved, Ameren Missouri intends to invest $123 million annually in the proposed customer energy-efficiency programs from 2025 to 2027. In addition, Ameren Missouri requested performance incentives applicable to each plan year to earn revenues by achieving certain customer energy-efficiency savings and target spending goals. If 100% of the goals are achieved, Ameren Missouri would earn performance incentive revenues totaling $56 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. In March 2024, the MoPSC staff and the MoOPC filed responses in opposition to the proposed customer energy-efficiency plan under the MEEIA. Ameren Missouri expects a decision by the MoPSC by October 2024, but cannot predict the ultimate outcome of this regulatory proceeding.

MISO Long-Range Transmission Projects CCN

In July 2022, the MISO approved the first tranche of projects related to a preliminary long-range transmission planning roadmap of projects through 2039. A portion of these projects were assigned or awarded via a competitive bid process to various utilities, including Ameren. In July 2024, ATXI filed a request for a CCN, among other things, with the MoPSC related to a portion of the MISO long-range transmission projects that it will construct within the MoPSC’s jurisdiction. A decision by the MoPSC is expected by mid-2025.

Illinois

MYRP

In December 2023, the ICC issued an order in Ameren Illinois' MYRP proceeding approving base rates for electric distribution services for 2024 through 2027 and rejecting Ameren Illinois' Grid Plan, which was addressed as part of the MYRP proceeding. Rate changes consistent with the December 2023 order became effective in January 2024 and remained effective through late June 2024, when new rates became effective pursuant to the June 2024 ICC rehearing order discussed below. The December 2023 order adopted an alternative methodology to establish a rate base and revenue requirements for the years 2024 through 2027 using Ameren Illinois’ previously approved 2022 year-end rate base. In January 2024, the ICC partially denied a rehearing requested by Ameren Illinois to revise the allowed ROE in the December 2023 order and granted Ameren Illinois’ rehearing request to reconsider the rate base for each year of the MYRP and to include a base level of investments to maintain grid reliability in each year of the MYRP. In June 2024, the ICC issued an order on Ameren Illinois’ rehearing request, which revised the rate bases for Ameren Illinois’ MYRP test years to include investments for 2023 through 2027, among other things. New rates became effective in late June 2024. For additional information on the ICC’s June 2024 rehearing order, see the table below. In July 2024, Ameren Illinois filed a request for rehearing of the ICC’s June 2024 rehearing order to include an asset associated with other postretirement benefits in the rate base. Subsequently, in August 2024, the ICC denied the rehearing request. The ICC rehearing denial

is subject to appeal. Also, in January 2024, Ameren Illinois filed an appeal of the December 2023 ICC order, including the 8.72% ROE, to the Illinois Appellate Court for the Fifth Judicial District. The court is under no deadline to address the appeal.

In July 2024, Ameren Illinois filed an update to its revised Grid Plan and revised MYRP to update the requested revenue requirements for 2024 through 2027. In July 2024, the ICC staff filed its recommendation regarding Ameren Illinois’ revised MYRP. An ICC decision on the revised Grid Plan and updated revenue requirements is expected by the end of 2024 with rates effective in January 2025.

The following table presents the approved revenue requirements and average annual rate base in the ICC’s June 2024 rehearing order, as well as the proposed revenue requirements and average annual rate base in Ameren Illinois’ July 2024 revised MYRP and the ICC staff’s July 2024 revised MYRP recommendation:


Year	Revenue Requirement (in millions)	Average Annual Rate Base (in billions)
ICC’s June 2024 Rehearing Order(a):
2024	$1,196	$4.0
2025	$1,282	$4.3
2026	$1,350	$4.5
2027	$1,397	$4.7
Ameren Illinois’ July 2024 Revised MYRP(a):
2024	$1,215	$4.3
2025	$1,300	$4.5
2026	$1,386	$4.8
2027	$1,446	$5.0
ICC Staff’s July 2024 Revised MYRP(a):
2024	$1,201	$4.2
2025	$1,281	$4.4
2026	$1,361	$4.6
2027	$1,414	$4.8

(a)Based on an allowed ROE of 8.72% and a capital structure composed of 50% common equity. The ROE is under appeal, as discussed above.

Using the 2023 revenue requirement as a starting point, the approved revenue requirements in the ICC’s June 2024 rehearing order represent a cumulative four-year increase of $285 million compared to a cumulative increase of $334 million in Ameren Illinois’ July 2024 revised MYRP and a cumulative increase of $302 million in the ICC staff’s July 2024 revised MYRP recommendation.

Ameren Illinois cannot predict the ultimate outcome of the appeal to the Illinois Appellate Court for the Fifth Judicial District, its revised Grid Plan filing, or its request to update the associated MYRP revenue requirements for 2024 through 2027.

2023 Electric Distribution Revenue Requirement Reconciliation Adjustment Request

In April 2024, Ameren Illinois filed for a reconciliation adjustment to its 2023 electric distribution service revenue requirement with the ICC. In July 2024, Ameren Illinois filed a revised reconciliation adjustment, requesting recovery of $158 million. The reconciliation adjustment reflects a capital structure composed of 50% common equity and Ameren Illinois’ actual 2023 recoverable costs and year-end rate base. In June 2024, the ICC staff submitted its calculation of the reconciliation adjustment, recommending recovery of $157 million. An ICC decision in this proceeding is required by December 2024, and any approved adjustment would be collected from customers in 2025. This is the final revenue requirement reconciliation under the IEIMA formula framework.

Electric Customer Energy-Efficiency Investments

In May 2024, Ameren Illinois filed its annual electric energy-efficiency formula rate update to increase its rates by $26 million with the ICC. An ICC decision in this proceeding is required by December 2024, with new rates effective January 2025.

2023 Natural Gas Delivery Service Rate Order

In November 2023, the ICC issued an order in Ameren Illinois’ January 2023 natural gas delivery service regulatory rate review, which resulted in an increase to its annual revenues for natural gas delivery service of $112 million based on a 9.44% allowed ROE, a capital structure composed of 50% common equity, and a rate base of approximately $2.85 billion. The order reflected a reduction of approximately $93 million of planned distribution and transmission capital investments included in Ameren Illinois’ requested revenue increase, which used a 2024 future test year. The new rates became effective on November 28, 2023.

In December 2023, Ameren Illinois filed a request for rehearing of the ICC’s November 2023 order. The filing requested the ICC revise the order to include an allowed ROE of at least 9.89%, a capital structure composed of 52% common equity, and the reversal of the approximately $93 million reduction of planned distribution and transmission capital investments included in the order, among other things. In January 2024, the ICC denied Ameren Illinois’ rehearing request. Subsequently, in January 2024, Ameren Illinois filed an appeal of the November 2023 ICC order to the Illinois Appellate Court for the Fifth Judicial District. The court is under no deadline to address the appeal. Ameren Illinois cannot predict the ultimate outcome of this appeal.

QIP Reconciliation Hearing

In March 2021, Ameren Illinois filed a request with the ICC to initiate a reconciliation proceeding to determine the accuracy and prudence of natural gas capital investments recovered under the QIP rider during 2020. In October 2023, the Illinois Attorney General’s office challenged the recovery of capital investments that were made during 2020, alleging that the ICC should disallow approximately $53 million in natural gas capital investments as improper and imprudent, providing a potential over-recovery of approximately $3 million in 2020. In October 2023, the ICC staff filed testimony that supports the prudence and reasonableness of the capital investments made during 2020. Ameren Illinois’ 2020 QIP rate recovery request under review by the ICC was within the rate increase limitations allowed by law. The ICC is under no deadline to issue an order in this proceeding. Ameren Illinois cannot predict the ultimate outcome of this regulatory proceeding.

MISO Long-Range Transmission Projects CCN

In July 2022, the MISO approved the first tranche of projects related to a preliminary long-range transmission planning roadmap of projects through 2039. A portion of these projects were assigned or awarded via a competitive bidding process to various utilities, including Ameren. In February 2024, Ameren Illinois and ATXI filed a request for a CCN, among other things, with the ICC related to the portion of the MISO long-range transmission projects they will construct within the ICC’s jurisdiction. A decision by the ICC is expected by mid-2025.

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. The currently allowed base ROE of 10.02% will remain effective for customer billings, but the transmission rates charged during previous periods and the currently effective rates may be 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 $21 million and $15 million, respectively, based on each company’s 2024 projected rate base. Ameren and Ameren Illinois are unable to predict the ultimate resolution of this matter; however, such resolution could have a material effect on their results of operations, financial position, and liquidity.

Short-Term Debt And Liquidity

6 Months Ended

Jun. 30, 2024

Debt Disclosure [Abstract]

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, of the Form 10-K for a description of our indebtedness provisions and other covenants as well as a description of money pool agreements.

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 June 30, 2024, 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 $1.9 billion. The Ameren Companies were in compliance with the covenants in their Credit Agreements as of June 30, 2024. As of June 30, 2024, the ratios of consolidated indebtedness to consolidated total capitalization, calculated in accordance with the provisions of the Credit Agreements, were 61%, 49%, and 45% for Ameren, Ameren Missouri, and Ameren Illinois, respectively.

The following table presents commercial paper outstanding, net of issuance discounts, as of June 30, 2024, and December 31, 2023. There were no borrowings outstanding under the Credit Agreements as of June 30, 2024, or December 31, 2023.


	June 30, 2024		December 31, 2023
Ameren (parent)	$	301	$	—
Ameren Missouri	390		170
Ameren Illinois	—		366
Ameren consolidated	$	691	$	536

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 six months ended June 30, 2024 and 2023:


	Ameren (parent)			Ameren Missouri			Ameren Illinois			Ameren Consolidated
2024
Average daily amount outstanding	$	84		$	109		$	385		$	578

Weighted-average interest rate	5.55		%	5.53		%	5.57		%	5.56		%
Peak amount outstanding during period(a)	$	301		$	509		$	694		$	1,084
Peak interest rate	5.60		%	5.68		%	5.68		%	5.68		%
2023
Average daily amount outstanding	$	595		$	343		$	230		$	1,168

Weighted-average interest rate	5.14		%	5.04		%	5.10		%	5.10		%
Peak amount outstanding during period(a)	$	841		$	592		$	450		$	1,381
Peak interest rate	5.55		%	5.55		%	5.60		%	5.60		%

(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 amount 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 and six months ended June 30, 2024, was 5.51% and 5.41%, respectively (2023 – 5.28% and 5.04%, respectively). See Note 8 – Related-party Transactions for the amount of interest income and expense from the utility money pool agreements recorded by Ameren Missouri and Ameren Illinois for the three and six months ended June 30, 2024 and 2023.

Long-Term Debt And Equity Financings	6 Months Ended
Long-Term Debt And Equity Financings	Jun. 30, 2024
Long-Term Debt And Equity Financings [Abstract]
LONG-TERM DEBT AND EQUITY FINANCINGS	LONG-TERM DEBT AND EQUITY FINANCINGS Ameren For the three and six months ended June 30, 2024, Ameren issued a total of 0.2 million and 0.3 million shares of common stock, under its DRPlus and 401(k) plan, and received proceeds of $4 million and $14 million, respectively. As of June 30, 2024, Ameren had a receivable of $7 million related to issuances of common stock under its DRPlus. In addition, in the first quarter of 2024, Ameren issued 0.2 million shares of common stock valued at $16 million upon the settlement of stock-based compensation awards. There were no shares issued under the ATM program for the three and six months ended June 30, 2024. As of June 30, 2024, Ameren had approximately $770 million of common stock available for sale under the ATM program, which takes into account the forward sale agreements in effect as of June 30, 2024, discussed below. The forward sale agreements outstanding as of June 30, 2024, can be settled at Ameren’s discretion on or prior to dates ranging from October 3, 2024 to February 28, 2025. 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 $76.69 to $89.31, with an average initial forward sale price of $80.45. 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 June 30, 2024, Ameren could have settled the forward sale agreements with physical delivery of 2.9 million shares of common stock to the respective counterparties in exchange for cash of $232 million. Alternatively, the forward sale agreements could have also been settled at June 30, 2024, with the counterparties delivering approximately $29 million of cash or approximately 0.4 million shares of common stock to Ameren. In connection with the forward sale agreements outstanding at June 30, 2024, the various counterparties, or their affiliates, borrowed from third parties and sold 2.9 million shares of common stock. The gross sales price of these shares totaled $232 million. Ameren has not received any proceeds from such sales of borrowed shares. The forward sale agreements have been classified as equity transactions. Ameren Missouri In January 2024, Ameren Missouri issued $350 million of 5.25% first mortgage bonds due January 2054, with interest payable semiannually on January 15 and July 15 of each year, beginning July 15, 2024. Net proceeds from this issuance were used for capital expenditures and to repay short-term debt. In April 2024, Ameren Missouri issued $500 million of 5.20% first mortgage bonds due April 2034, with interest payable semiannually on April 1 and October 1 of each year, beginning October 1, 2024. Net proceeds from this issuance were used for capital expenditures and to repay short-term debt. In April 2024, $350 million principal amount of Ameren Missouri’s 3.50% senior secured notes matured and were repaid with cash on hand. Ameren Missouri received capital contributions totaling $350 million from Ameren (parent) during the three and six months ended June 30, 2024. Ameren Illinois In June 2024, Ameren Illinois issued $625 million of 5.55% first mortgage bonds due July 2054, with interest payable semiannually on January 1 and July 1 of each year, beginning January 1, 2025. Net proceeds from this issuance were used to repay short-term debt. Indenture Provisions and Other Covenants See Note 5 – Long-term Debt and Equity Financings under Part II, Item 8, of the Form 10-K for a description of our indenture provisions and other covenants, as well as restrictions on the payment of dividends. At June 30, 2024, 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 June 30, 2024, none of the Ameren Companies had any material off-balance-sheet financing arrangements, other than their 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

6 Months Ended

Jun. 30, 2024

Other Nonoperating Income (Expense) [Abstract]

OTHER INCOME, NET

The following table presents the components of “Other Income, Net” in the Ameren Companies’ statements of income for the three and six months ended June 30, 2024 and 2023:


	Three Months				Six Months
	2024		2023		2024		2023
Ameren:

Allowance for equity funds used during construction	$	16	$	14	$	25	$	23
Other interest income	13		9		21		17

Non-service cost components of net periodic benefit income(a)	76		63		152		127
Miscellaneous income	4		2		6		4
Earnings related to equity method investments	1		—		1		2
Donations	(2)		(2)		(4)		(4)
Miscellaneous expense	(5)		(4)		(9)		(9)
Total Other Income, Net	$	103	$	82	$	192	$	160
Ameren Missouri:

Allowance for equity funds used during construction	$	14	$	8	$	23	$	12
Other interest income	3		2		5		6
Non-service cost components of net periodic benefit income(a)	35		14		69		28
Miscellaneous income	—		1		2		2
Donations	(1)		(1)		(2)		(2)
Miscellaneous expense	(2)		(2)		(4)		(5)
Total Other Income, Net	$	49	$	22	$	93	$	41
Ameren Illinois:

Allowance for equity funds used during construction	$	2	$	6	$	2	$	10
Other interest income	9		6		15		10

Non-service cost components of net periodic benefit income	26		31		53		62
Miscellaneous income	2		1		3		2
Donations	(1)		(1)		(2)		(2)
Miscellaneous expense	(1)		(2)		(3)		(4)
Total Other Income, Net	$	37	$	41	$	68	$	78

(a)For the three and six months ended June 30, 2024, the non-service cost components of net periodic benefit income were adjusted by amounts deferred of $(11) million and $(20) 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. The deferral was $17 million and $34 million, respectively, for the three and six months ended June 30, 2023. See Note 11 – Retirement Benefits for additional information.

Derivative Financial Instruments

6 Months Ended

Jun. 30, 2024

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 June 30, 2024, and December 31, 2023, all contracts that met the definition of a derivative and were not eligible for the NPNS exception received regulatory deferral. The cash flows from our derivative financial instruments follow the cash flow classification of the hedged item.

The following table presents open gross commodity contract volumes by commodity type for derivative assets and liabilities as of June 30, 2024, and December 31, 2023. As of June 30, 2024, these contracts extended through October 2027, October 2029 and May 2032 for fuel oils, natural gas and power, respectively.


	Quantity (in millions)
	June 30, 2024			December 31, 2023
Commodity	Ameren Missouri	Ameren Illinois	Ameren	Ameren Missouri	Ameren Illinois	Ameren
Fuel oils (in gallons)	20	—	20	17	—	17
Natural gas (in mmbtu)	52	221	273	53	218	271
Power (in MWhs)	—	5	5	—	5	5
Uranium (pounds in thousands)	—	—	—	186	—	186

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 June 30, 2024, and December 31, 2023:


		June 30, 2024						December 31, 2023
	Balance Sheet Location	Ameren Missouri		Ameren Illinois		Ameren			Ameren Missouri		Ameren Illinois		Ameren







Fuel oils	Other current assets	$	2	$	—	$	2		$	2	$	—	$	2



Natural gas	Other current assets	1		3		4			—		—		—
	Other assets	2		1		3			3		3		6


Power	Other current assets	15		—		15			5		—		5



Uranium	Other current assets	—		—		—			9		—		9

	Total assets	$	20	$	4	$	24		$	19	$	3	$	22


Fuel oils	Other current liabilities	$	1	$	—	$	1		$	1	$	—	$	1
	Other deferred credits and liabilities	—		—		—			1		—		1


Natural gas	Other current liabilities	9		33		42			12		45		57
	Other deferred credits and liabilities	8		28		36			10		30		40


Power	Other current liabilities	1		11		12			1		12		13
	Other deferred credits and liabilities	—		50		50			—		56		56




	Total liabilities	$	19	$	122	$	141		$	25	$	143	$	168

We believe that entering into master netting arrangements or similar agreements mitigates the level of financial loss that could result from default by allowing net settlement of derivative assets and liabilities. These master netting arrangements allow the counterparties to net settle sale and purchase transactions. Further, collateral requirements are calculated at the master netting arrangement or similar agreement level by counterparty.

The following table provides the recognized gross derivative balances and the net amounts of those derivatives subject to an enforceable master netting arrangement or similar agreement as of June 30, 2024, and December 31, 2023:


			Gross Amounts Not Offset in the Balance Sheet
Commodity Contracts Eligible to be Offset	Gross Amounts Recognized in the Balance Sheet		Derivative Instruments		Cash Collateral Received/Posted(a)		Net Amount
June 30, 2024
Assets:
Ameren Missouri	$	20	$	5	$	—	$	15
Ameren Illinois	4		2		—		2
Ameren	$	24	$	7	$	—	$	17
Liabilities:
Ameren Missouri	$	19	$	5	$	—	$	14
Ameren Illinois	122		2		—		120
Ameren	$	141	$	7	$	—	$	134
December 31, 2023
Assets:
Ameren Missouri	$	19	$	6	$	—	$	13
Ameren Illinois	3		1		—		2
Ameren	$	22	$	7	$	—	$	15
Liabilities:
Ameren Missouri	$	25	$	6	$	—	$	19
Ameren Illinois	143		1		6		136
Ameren	$	168	$	7	$	6	$	155

(a)Cash collateral received reduces gross asset balances and is included in “Other current liabilities” and “Other deferred credits and liabilities” on the balance sheet. Cash collateral posted reduces gross liability balances and is included in “Other current assets” and “Other assets” on the balance sheet.

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 June 30, 2024, 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 June 30, 2024, 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 Collateral Posted		Potential Aggregate Amount of Additional Collateral Required(b)
Ameren Missouri	$	19	$	—	$	13
Ameren Illinois	61		—		59
Ameren	$	80	$	—	$	72

(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

6 Months Ended

Jun. 30, 2024

Fair Value Disclosures [Abstract]

Fair Value Disclosures

FAIR VALUE MEASUREMENTS

Fair value is defined as the price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. 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 and six months ended June 30, 2024 or 2023. At June 30, 2024, and December 31, 2023, 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 June 30, 2024, and December 31, 2023:


		June 30, 2024									December 31, 2023
		Level 1		Level 2		Level 3		Total			Level 1		Level 2		Level 3		Total
Assets:
Ameren Missouri
	Derivative assets – commodity contracts:
	Fuel oils	$	1	$	—	$	1	$	2		$	2	$	—	$	—	$	2
	Natural gas	—		3		—		3			—		3		—		3
	Power	—		—		15		15			—		—		5		5
	Uranium	—		—		—		—			—		—		9		9
	Total derivative assets – commodity contracts	$	1	$	3	$	16	$	20		$	2	$	3	$	14	$	19
	Nuclear decommissioning trust fund:

	Equity securities:
	U.S. large capitalization	$	842	$	—	$	—	$	842		$	787	$	—	$	—	$	787
	Debt securities:
	U.S. Treasury and agency securities	—		178		—		178			—		150		—		150
	Corporate bonds	—		154		—		154			—		136		—		136


	Other	—		82		—		82			—		68		—		68
	Total nuclear decommissioning trust fund	$	842	$	414	$	—	$	1,256	(a)	$	787	$	354	$	—	$	1,141	(a)
	Total Ameren Missouri	$	843	$	417	$	16	$	1,276		$	789	$	357	$	14	$	1,160
Ameren Illinois
	Derivative assets – commodity contracts:
	Natural gas	—		1		3		4			—		1		2		3

	Total Ameren Illinois	$	—	$	1	$	3	$	4		$	—	$	1	$	2	$	3
Ameren
	Derivative assets – commodity contracts(b)	$	1	$	4	$	19	$	24		$	2	$	4	$	16	$	22
	Nuclear decommissioning trust fund(c)	842		414		—		1,256		(a)	787		354		—		1,141		(a)
	Total Ameren	$	843	$	418	$	19	$	1,280		$	789	$	358	$	16	$	1,163
Liabilities:
Ameren Missouri
	Derivative liabilities – commodity contracts:
	Fuel oils	$	1	$	—	$	—	$	1		$	2	$	—	$	—	$	2
	Natural gas	—		16		1		17			—		19		3		22
	Power	—		—		1		1			—		—		1		1

	Total Ameren Missouri	$	1	$	16	$	2	$	19		$	2	$	19	$	4	$	25
Ameren Illinois
	Derivative liabilities – commodity contracts:
	Natural gas	$	2	$	52	$	7	$	61		$	4	$	60	$	11	$	75
	Power	—		—		61		61			—		—		68		68
	Total Ameren Illinois	$	2	$	52	$	68	$	122		$	4	$	60	$	79	$	143
Ameren
	Derivative liabilities – commodity contracts(b)	$	3	$	68	$	70	$	141		$	6	$	79	$	83	$	168

(a)Balance excludes $10 million and $9 million of cash and cash equivalents, receivables, payables, and accrued income, net, for June 30, 2024, and December 31, 2023, 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 and six months ended June 30, 2024 and 2023:


	2024						2023
	Ameren Missouri		Ameren Illinois		Ameren			Ameren Missouri		Ameren Illinois		Ameren
For the three months ended June 30:
Beginning balance at April 1	$	2	$	(54)	$	(52)		$	5	$	(52)	$	(47)
Realized and unrealized gains/(losses) included in regulatory assets/liabilities	15		(12)		3			14		(20)		(6)


Settlements	(3)		5		2			(5)		4		(1)


Ending balance at June 30	$	14	$	(61)	$	(47)		$	14	$	(68)	$	(54)
Change in unrealized gains/(losses) related to assets/liabilities held at June 30	$	14	$	(12)	$	2		$	14	$	(20)	$	(6)
For the six months ended June 30:
Beginning balance at January 1	$	4	$	(68)	$	(64)		$	12	$	(33)	$	(21)
Realized and unrealized gains/(losses) included in regulatory assets/liabilities	14		(2)		12			8		(41)		(33)


Settlements	(4)		9		5			(6)		6		—


Ending balance at June 30	$	14	$	(61)	$	(47)		$	14	$	(68)	$	(54)
Change in unrealized gains/(losses) related to assets/liabilities held at June 30	$	14	$	—	$	14		$	14	$	(35)	$	(21)

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 June 30, 2024, and December 31, 2023:


			Fair Value						Weighted Average(b)
	Commodity		Assets		Liabilities	Valuation Technique(s)	Unobservable Input(a)	Range
2024	Power(c)	$	15	$	(62)	Discounted cash flow	Average forward peak and off-peak pricing – forwards/swaps ($/MWh)	33 – 70	43

							Nodal basis ($/MWh)	(10) – (1)	(5)


2023	Power(c)	$	5	$	(69)	Discounted cash flow	Average forward peak and off-peak pricing – forwards/swaps ($/MWh)	31 – 65	43

							Nodal basis ($/MWh)	(8) – (1)	(5)

(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.

The following table sets forth the carrying amount and, by level within the fair value hierarchy, the fair value of long-term debt (including current portion) disclosed, but not recorded, at fair value as of June 30, 2024, and December 31, 2023:


Long-Term Debt (Including Current Portion):	Carrying Amount(a)		Fair Value
			Level 2		Level 3			Total
	June 30, 2024




Ameren	$	17,079	$	14,990	$	460	(b)	$	15,450






Ameren Missouri	6,830		6,069		—			6,069





Ameren Illinois	5,851		5,251		—			5,251
	December 31, 2023



Ameren	$	15,970	$	14,366	$	467	(b)	$	14,833






Ameren Missouri	6,341		5,800		—			5,800




Ameren Illinois	5,232		4,867		—			4,867

(a)Included unamortized debt issuance costs, which were excluded from the fair value measurement, of $124 million, $53 million, and $52 million for Ameren, Ameren Missouri, and Ameren Illinois, respectively, as of June 30, 2024. Included unamortized debt issuance costs, which were excluded from the fair value measurement, of $111 million, $45 million, and $47 million for Ameren, Ameren Missouri, and Ameren Illinois, respectively, as of December 31, 2023.

(b)The Level 3 fair value amount consists of ATXI’s senior unsecured notes.

The Ameren Companies’ carrying amounts of cash, cash equivalents, and restricted cash approximate fair value and are considered Level 1 in the fair value hierarchy. The Ameren Companies’ short-term borrowings approximate fair value because of the short-term nature of these instruments and are considered Level 2 in the fair value hierarchy.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Related Party Transactions

6 Months Ended

Jun. 30, 2024

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 agreements, 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 $22 million and $24 million, respectively, as of June 30, 2024, and $31 million and $34 million, respectively, as of December 31, 2023, related to Ameren Services’ allocated portion of Ameren’s pension and postretirement benefit plans.

In December 2023, ATXI placed in service a transmission operations control center. Rental revenues received by ATXI from Ameren Services associated with this facility are affiliate transactions and are eliminated in consolidation for Ameren’s consolidated financial statements. Ameren Services’ rental expenses incurred are subsequently allocated to Ameren Missouri and Ameren Illinois as part of the Ameren Services support agreement.

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 June 30, 2024, and December 31, 2023:


	June 30, 2024				December 31, 2023
	Ameren Missouri		Ameren Illinois		Ameren Missouri		Ameren Illinois
Income taxes payable to parent(a)	$	—	$	44	$	—	$	2
Income taxes receivable from parent(b)	54		—		56		22

(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 and six months ended June 30, 2024 and 2023:


				Three Months				Six Months
Agreement	Income Statement Line Item			Ameren Missouri		Ameren Illinois		Ameren Missouri		Ameren Illinois
Ameren Missouri power supply	Operating Revenues	2024	$	(b)	$	(a)	$	(b)	$	(a)
agreements with Ameren Illinois		2023		(b)		(a)		(b)		(a)
Ameren Missouri and Ameren Illinois	Operating Revenues	2024	$	8	$	(b)	$	15	$	(b)
rent and facility services		2023		8		(b)		18		(b)
Ameren Missouri and Ameren Illinois miscellaneous	Operating Revenues	2024	$	1	$	(b)	$	1	$	1
support services		2023		(b)		(b)		(b)		(b)
Total Operating Revenues		2024	$	9	$	(b)	$	16	$	1
		2023		8		(b)		18		(b)
Ameren Illinois power supply	Purchased Power	2024	$	(a)	$	(b)	$	(a)	$	(b)
agreements with Ameren Missouri		2023		(a)		(b)		(a)		(b)
Ameren Missouri and Ameren Illinois	Purchased Power	2024	$	2	$	1	$	4	$	1
transmission services from ATXI		2023		1		(b)		1		(b)
Total Purchased Power		2024	$	2	$	1	$	4	$	1
		2023		1		(b)		1		(b)
Ameren Missouri and Ameren Illinois	Other Operations and Maintenance	2024	$	(b)	$	(b)	$	(b)	$	(b)
rent and facility services		2023		(b)		(b)		(b)		2
Ameren Services support services	Other Operations and Maintenance	2024	$	43	$	40	$	81	$	77
agreement		2023		35		33		70		68
Total Other Operations and		2024	$	43	$	40	$	81	$	77
Maintenance		2023		35		33		70		70
Money pool interest	(Interest Charges)/Other Income, Net	2024	$	(b)	$	(b)	$	(3)	$	(2)
		2023		(b)		(b)		(b)		(b)

(a)Not applicable.

(b)Amount less than $1 million.

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-5

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
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-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-6

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
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-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481062/946-235-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
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-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481062/946-235-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
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-Paragraph 1
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(g)(3))
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-URI https://asc.fasb.org//1943274/2147483575/946-220-S99-1

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
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-Name Accounting Standards Codification
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-Paragraph 1
-Subparagraph (SX 210.6-07(2)(c))
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-URI https://asc.fasb.org//1943274/2147483575/946-220-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(e))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483575/946-220-S99-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-Name Accounting Standards Codification
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-URI https://asc.fasb.org//850/tableOfContent

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
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-Section 50
-Paragraph 6
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-URI https://asc.fasb.org//1943274/2147483326/850-10-50-6

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
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-Paragraph 1
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-URI https://asc.fasb.org//1943274/2147483326/850-10-50-1

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
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-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483326/850-10-50-1

+ Details

Commitments And Contingencies	6 Months Ended
Commitments And Contingencies	Jun. 30, 2024
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 energy-related 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 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 SO2, particulate matter, NOx, mercury, toxic metals and acid gases, and CO2 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 those 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. Since 2021, Ameren Missouri’s High Prairie Renewable Energy Center curtailed nighttime operations from April through October to limit impacts on protected species during the critical biological season. Seasonal nighttime curtailment began again in April 2024, but the extent and duration of the curtailment is currently unknown as assessment of mitigation technologies is ongoing. Ameren Missouri does not anticipate these operating curtailments will 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 2024 through 2028 to comply with environmental regulations. These estimates exclude capital expenditures that may be necessary to comply with regulations issued by the EPA in 2024 relating to CO2 emissions, MATS, effluent limitations guidelines, and CCR management, which Ameren and Ameren Missouri are assessing and are discussed below. Additional capital expenditures for environmental controls beyond 2028 could be required. This estimate of capital expenditures includes surface impoundment closure and corrective action measures required by the 2015 CCR Rule and modifications to cooling water intake structures at existing power plants under Clean Water Act rules in place prior to 2024, all of which are discussed below. In addition to planned retirements of coal-fired energy centers identified in the 2023 IRP filed with the MoPSC in September 2023 and as noted below with respect to the NSR and Clean Air Act litigation and Illinois emissions standards discussed in Note 14 – Commitments and Contingencies under Part II, Item 8, of the Form 10-K, 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 statutes and regulations 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 regulations. Clean Air Act Federal and state laws, including the CSAPR, regulate emissions of SO2 and NOx through the reduction of emissions at their source and the use and retirement of emission allowances. In April 2022, the EPA proposed the Good Neighbor Rule of the Clean Air Act, which includes additional NOx 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 Rule 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, which were subsequently published to the Federal Register in June 2023, reducing the amount of NOx allowances available for state budgets and imposing NOx emission limits on electric generating units for Missouri, Illinois, and other states under the Good Neighbor Rule of the Clean Air Act. In April 2023, the Missouri Attorney General and Ameren Missouri separately filed lawsuits in the United States Court of Appeals for the Eighth Circuit challenging the EPA’s disapproval of the Missouri state plan and sought a stay of the EPA’s disapproval of the Missouri state plan. The United States Court of Appeals for the Eighth Circuit in May 2023 granted those stay motions thereby preventing the EPA from imposing the federal implementation plan until the court of appeals issues a ruling. In June 2024, the United States Supreme Court granted applications to stay the EPA’s imposition of the federal implementation plan until resolution of appellate court challenges. Ameren Missouri complies 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 existing NOx air pollution control equipment. Reducing the amount of state budget NOx allowances for compliance with NOx emission limits could result in additional controls being required on Ameren Missouri’s generating units and/or the reduction of operations. Any additional costs for compliance are expected to be recovered from customers, subject to MoPSC prudence review, through the FAC or higher base rates. CO2 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 the EPA’s proposed rules were designed to shift generation from fossil-fuel-fired power plants to renewable energy facilities, which was improper absent specific congressional authorization. In response to that ruling, in April 2024, the EPA issued a final rule that sets CO2 emission standards for existing coal-fired and new natural gas-fired power plants that relies on the adoption of carbon capture technology and/or natural gas co-firing for coal-fired power plants and carbon capture technology for new natural gas-fired power plants. Affected power plants are required to comply with the rule through a phased-in approach or retire. In July 2024, the United States Court of Appeals for the District of Columbia Circuit denied a request for stay by various stakeholders including state attorney generals and industry groups but indicated it would establish an expedited schedule regarding the legal merits of the final rule. Subsequently in July 2024, motions for stay of the final rule were filed with the United States Supreme Court. Ameren and Ameren Missouri are monitoring the legal challenges and assessing the impacts of the final rule and, at this time, cannot predict the impacts on their results of operations, financial position, and liquidity. MATS In April 2024, the EPA revised the MATS by establishing a more stringent standard for emissions of particulate matter, requiring the use of continuous emissions monitoring systems. Ameren and Ameren Missouri are assessing the impacts of the revised rule and, at this time, cannot predict the impacts on their results of operations, financial position, and liquidity. 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 September 2023, the district court granted Ameren Missouri’s request to modify the remedy order to allow the retirement of the Rush Island Energy Center in advance of its previously expected retirement date of 2039 in lieu of installing a flue gas desulfurization system. In its amended remedy order, the district court established an October 15, 2024 retirement date to allow for the completion of various transmission reliability projects and, in the interim, authorized Ameren Missouri to operate the energy center only as needed and as directed by the MISO. The United States Department of Justice is seeking an order from the district court providing for additional mitigation relief related to prior emissions. Ameren Missouri contends that the retirement of the Rush Island Energy Center, which eliminates all future emissions from the energy center, mitigates claims relating to prior emissions. In March 2024, the district court ordered Ameren Missouri and the United States Department of Justice to file proposed draft orders outlining additional mitigation relief. In May 2024, Ameren Missouri filed a proposed draft order that includes retiring the Rush Island Energy Center, a program to provide electric buses and charging stations to schools in the metro St. Louis area, a program to provide air filters to eligible Ameren Missouri electric residential customers, and the retirement of SO2 allowances. Excluding the accelerated retirement of the Rush Island Energy Center, these programs are estimated to cost approximately $20 million. Also in May 2024, the United States Department of Justice filed a proposed draft order that includes a program to provide electric buses and charging stations to schools in the metro St. Louis area and a program to provide air filters to eligible Ameren Missouri electric residential customers. These programs include a significantly greater number of buses, charging stations, and air filters than Ameren Missouri’s proposal and the United States Department of Justice estimates these programs would cost approximately $120 million. A mediation proceeding related to the potential additional mitigation relief is scheduled for September 2024. As of June 30, 2024, Ameren and Ameren Missouri recorded a $20 million liability in “Other current liabilities” on their consolidated balance sheets related to the cost of potential additional mitigation, which represents the estimated minimum liability, as no other amount within the range was a better estimate. Ameren Missouri could be required to implement some or all of the additional mitigation relief programs included in the United States Department of Justice’s proposed draft order, the costs of which could be material and could adversely impact Ameren and Ameren Missouri’s results of operations and financial position. Depending on the scope and basis of any final order issued by the district court, which is expected by the end of 2024, Ameren Missouri or the United States Department of Justice could appeal any additional mitigation relief ordered. The MISO designated the Rush Island Energy Center as a system support resource in 2022 and concluded that certain reliability mitigation measures, including transmission upgrades, should occur before the energy center is retired. The Rush Island Energy Center began operating as a system support resource on September 1, 2022. In 2024, the MISO extended the system support resource designation through Rush Island Energy Center’s retirement date of October 15, 2024. In July 2024, an agreement between Ameren Missouri and the MISO was filed with the FERC for approval regarding the continued operation of the energy center during peak demand times and emergencies. Construction activities are ongoing for the transmission upgrades approved by the MISO, with the majority of the upgrades expected to be completed in the fall of 2024. Ameren Missouri expects to complete the last of the necessary upgrades by mid-2025. 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 Part II, Item 8, of the Form 10-K for additional information. In connection with the accelerated retirement of the Rush Island Energy Center, the MoPSC issued an order in June 2024 authorizing Ameren Missouri 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. Costs associated with the retirement would exclude any additional mitigation relief ordered in the NSR and Clean Air Act litigation discussed above. See Note 2 – Rate and Regulatory Matters for additional information. As of June 30, 2024, the Rush Island Energy Center had a net plant balance of $508 million included in plant to be abandoned, net, within “Property, Plant, and Equipment, Net”. 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. Clean Water Act Among other items, the Clean Water Act requires 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 this 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. In April 2024, the EPA issued new effluent limitation guidelines that established a zero discharge limit for flue gas desulfurization wastewater, bottom ash transport water, and combustion residual leachate. Ameren and Ameren Missouri expect the impacts of the new guidelines on their results of operations, financial position, and liquidity to be immaterial. CCR Management The EPA’s 2015 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, with closures of surface impoundments in process at its Sioux Energy Center and retired Meramec Energy Center. Ameren Missouri plans to substantially complete the closures of remaining surface impoundments by the end of 2026. Ameren Missouri’s CCR management compliance plan includes installation of groundwater monitoring equipment and groundwater treatment facilities. In April 2024, the EPA revised the CCR Rule to impose groundwater monitoring, and corrective action, closure, and post-closure requirements on certain active and inactive CCR surface impoundments and management disposal units. Ameren and Ameren Missouri have AROs of $42 million associated with CCR storage facilities recorded on their respective balance sheets as of June 30, 2024. This amount includes an immaterial incremental ARO related to the 2024 CCR Rule, which will be revised as additional site studies are performed. Ameren and Ameren Missouri are assessing the impacts of this rule revision and, at this time, cannot predict the final impacts on their results of operations, financial position, and liquidity. 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 June 30, 2024, Ameren Illinois has remediated the majority of the 44 former MGP sites in Illinois with an estimated remaining obligation primarily related to three of these former MGP sites at $45 million to $95 million. Ameren and Ameren Illinois recorded a liability of $45 million to represent the estimated minimum obligation for these sites, as no other amount within the range was a better estimate. Ameren cannot estimate the completion date of the estimated remaining obligation due to site accessibility, among other things. 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 impacted, regulatory changes, local ordinances, and site accessibility. The actual costs and timing of completion may vary substantially from these estimates. The ICC allows Ameren Illinois to recover MGP 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. 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

6 Months Ended

Jun. 30, 2024

Nuclear Waste Matters [Abstract]

CALLAWAY ENERGY CENTER

See 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 December 2023 and is reflected within the ARO. Ameren Missouri’s filing supported no change in electric service rates for decommissioning costs. There is no deadline by which the MoPSC must issue an order regarding the filing. 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, 2024:


Type and Source of Coverage	Most Recent Renewal Date	Maximum Coverages			Maximum Assessments for Single Incidents
Public liability and nuclear worker liability:
American Nuclear Insurers	January 1, 2024	$	500		$	—
Pool participation	(a)	15,763		(a)	166		(b)
		$	16,263	(c)	$	166
Property damage:
NEIL and EMANI	April 1, 2024	$	3,200	(d)	$	28	(e)
Accidental outage:
NEIL	April 1, 2024	$	490	(f)	$	11	(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 $500 million in the event of an incident at any licensed United States commercial reactor, payable at $24.7 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 $0.7 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 $291 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 October 2023. 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

6 Months Ended

Jun. 30, 2024

Retirement Benefits [Abstract]

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 and six months ended June 30, 2024 and 2023:


	Pension Benefits								Postretirement Benefits
	Three Months				Six Months				Three Months				Six Months
	2024		2023		2024		2023		2024		2023		2024		2023
Service cost(a)	$	23	$	23	$	44	$	46	$	3	$	3	$	6	$	6
Non-service cost components:
Interest cost	56		56		111		111		11		12		22		23
Expected return on plan assets(b)	(82)		(84)		(164)		(167)		(23)		(23)		(46)		(46)
Amortization of(b):

Prior service benefit	—		—		—		—		(1)		(1)		(2)		(2)
Actuarial (gain)	(16)		(28)		(33)		(57)		(10)		(12)		(20)		(23)
Total non-service cost components(c)	$	(42)	$	(56)	$	(86)	$	(113)	$	(23)	$	(24)	$	(46)	$	(48)

Net periodic benefit income(d)	$	(19)	$	(33)	$	(42)	$	(67)	$	(20)	$	(21)	$	(40)	$	(42)

(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 and six months ended June 30, 2024 and 2023:


	Pension Benefits								Postretirement Benefits
	Three Months				Six Months				Three Months				Six Months
	2024		2023		2024		2023		2024		2023		2024		2023
Ameren Missouri(a)	$	(10)	$	(17)	$	(22)	$	(35)	$	(7)	$	(7)	$	(14)	$	(15)
Ameren Illinois	(8)		(13)		(17)		(27)		(13)		(14)		(26)		(27)
Other	(1)		(3)		(3)		(5)		—		—		—		—
Ameren(a)	$	(19)	$	(33)	$	(42)	$	(67)	$	(20)	$	(21)	$	(40)	$	(42)

(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.

- Definition

The entire disclosure for retirement benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 70
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Income Taxes

6 Months Ended

Jun. 30, 2024

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 and six months ended June 30, 2024 and 2023:


	Ameren				Ameren Missouri				Ameren Illinois
	2024		2023		2024		2023		2024		2023
Three Months
Federal statutory corporate income tax rate	21	%	21	%	21	%	21	%	21	%	21	%
Increases (decreases) from:
Amortization of excess deferred taxes(a)	(8)		(7)		(14)		(15)		(4)		(2)

Renewable and other tax credits(b)	(4)		(5)		(8)		(10)		—		—
State tax	5		5		3		3		7		7
Depreciation differences	(1)		—		(1)		—		—		(1)



Effective income tax rate	13	%	14	%	1	%	(1)	%	24	%	25	%
Six Months
Federal statutory corporate income tax rate	21	%	21	%	21	%	21	%	21	%	21	%
Increases (decreases) from:

Amortization of excess deferred taxes(a)	(8)		(8)		(14)		(15)		(4)		(2)

Renewable and other tax credits(b)	(4)		(4)		(8)		(10)		—		—
State tax	5		5		3		3		7		7

Depreciation differences	—		—		—		—		—		(1)
Other permanent items	—		(1)		—		—		—		—
Effective income tax rate	14	%	13	%	2	%	(1)	%	24	%	25	%

(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.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//740/tableOfContent

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-14

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-21

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 270
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482526/740-270-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 17
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-17

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479360/740-10-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479360/740-10-S99-2

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482603/740-30-50-2

+ Details

Supplemental Information

6 Months Ended

Jun. 30, 2024

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 June 30, 2024, and December 31, 2023:


	June 30, 2024						December 31, 2023
	Ameren		Ameren Missouri		Ameren Illinois		Ameren		Ameren Missouri		Ameren Illinois
“Cash and cash equivalents”	$	19	$	—	$	6	$	25	$	—	$	—

Restricted cash included in “Other current assets”	18		7		7		13		5		5
Restricted cash included in “Other assets”	260		—		260		229		—		229
Restricted cash included in “Nuclear decommissioning trust fund”	4		4		—		5		5		—
Total cash, cash equivalents, and restricted cash	$	301	$	11	$	273	$	272	$	10	$	234

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 June 30, 2024, and December 31, 2023, “Other current liabilities” on Ameren’s and Ameren Illinois’ balance sheets included payables for purchased receivables of $49 million and $42 million, respectively.

The following table provides a reconciliation of the beginning and ending amount of the allowance for doubtful accounts for the three and six months ended June 30, 2024 and 2023:


	Three Months				Six Months
	2024		2023		2024		2023
Ameren:
Beginning of period	$	37	$	34	$	30	$	31
Bad debt expense	6		13		16		23
Charged to other accounts(a)	1		1		4		1
Net write-offs	(7)		(9)		(13)		(16)
End of period	$	37	$	39	$	37	$	39
Ameren Missouri:
Beginning of period	$	11	$	12	$	12	$	13
Bad debt expense	4		2		5		4
Net write-offs	(3)		(2)		(5)		(5)
End of period	$	12	$	12	$	12	$	12
Ameren Illinois:(b)
Beginning of period	$	26	$	22	$	18	$	18
Bad debt expense	2		11		11		19
Charged to other accounts(a)	1		1		4		1
Net write-offs	(4)		(7)		(8)		(11)
End of period	$	25	$	27	$	25	$	27

(a)Amounts associated with the allowance for doubtful accounts related to receivables purchased by Ameren Illinois from alternative retail electric suppliers, as required by the Illinois Public Utilities Act.

(b)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. The table above does not include the impact related to the riders.

Supplemental Cash Flow Information

The following table provides noncash financing and investing activity excluded from the statements of cash flows for the six months ended June 30, 2024 and 2023:


	June 30, 2024						June 30, 2023
	Ameren		Ameren Missouri				Ameren Illinois	Ameren		Ameren Missouri		Ameren Illinois
Investing:
Accrued capital expenditures, including nuclear fuel expenditures	$	380	$	232	$	134		$	325	$	132	$	173

Net realized and unrealized gain – nuclear decommissioning trust fund	103		103		—			105		105		—
Return of investment in industrial development revenue bonds(a)	—		—		—			240		240		—
Financing:
Issuance of common stock for stock-based compensation	$	16	$	—	$	—		$	37	$	—	$	—
Issuance of common stock under the DRPlus	7		—		—			7		—		—
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 six months ended June 30, 2024:


	Ameren Missouri			Ameren Illinois			Ameren
Balance at December 31, 2023	$	787	(a)	$	4	(b)	$	791	(a)
Liabilities incurred	7		(c)	—			7		(c)
Liabilities settled	(4)			(1)			(5)
Accretion	17		(d)	—			17		(d)

Balance at June 30, 2024	$	807	(a)	$	3	(b)	$	810	(a)

(a)Balance included $19 million in “Other current liabilities” on the balance sheet as of both June 30, 2024, and December 31, 2023.

(b)Included in “Other deferred credits and liabilities” on the balance sheet.

(c)In June 2024, Ameren and Ameren Missouri recorded an ARO related to the decommissioning for the Cass County Solar Project. In addition, as a result of the 2024 CCR Rule, Ameren and Ameren Missouri recorded an immaterial increase to their AROs associated with CCR storage facilities. See Note 9 – Commitments and Contingencies for additional information.

(d)Accretion expense attributable to Ameren Missouri was recorded as a decrease to regulatory liabilities.

Stock-based Compensation

In the first quarter of 2024, Ameren granted 359,133 performance share units with a grant date fair value of $21 million and 153,887 restricted share units with a grant date fair value of $11 million. Awards vest approximately 3 years after the grant date based on continued employment 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 (307,816 performance share units) or clean energy transition targets (51,317 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 six months ended June 30, 2024 and 2023, excess tax benefits (deficiencies) associated with the settlement of stock-based compensation awards increased income tax expense by $1 million and reduced income tax expense by $6 million, respectively.

Deferred Compensation

At June 30, 2024, and December 31, 2023, the present value of benefits to be paid for deferred compensation obligations was $80 million and $85 million, respectively, which was primarily reflected in “Other deferred credits and liabilities” on Ameren’s consolidated balance sheet.

Operating Revenues

As of June 30, 2024 and 2023, 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 and six months ended June 30, 2024 and 2023:


	Three Months				Six Months
	2024		2023		2024		2023
Ameren Missouri	$	41	$	39	$	76	$	73
Ameren Illinois	28		26		65		63
Ameren	$	69	$	65	$	141	$	136

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 and six months ended June 30, 2024 and 2023:


	Three Months		Six Months
	2024	2023	2024	2023


Weighted-average Common Shares Outstanding – Basic	266.7	262.6	266.5	262.4
Assumed settlement of performance share units and restricted stock units	0.1	0.6	0.3	0.8

Weighted-average Common Shares Outstanding – Diluted(a)	266.8	263.2	266.8	263.2

(a)There was an immaterial number of anti-dilutive performance share units excluded from the earnings per diluted share calculations for the three and six months ended June 30, 2024 and 2023. The outstanding forward sale agreements as of June 30, 2024 and 2023, were anti-dilutive for the three and six months ended June 30, 2024 and 2023, and were excluded from the earnings per diluted share calculation as calculated using the treasury stock method. For additional information about the outstanding forward sale agreements, see Note 4 – Long-term Debt and Equity Financings.

Segment Information

6 Months Ended

Jun. 30, 2024

Segment Reporting [Abstract]

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 and six months ended June 30, 2024 and 2023. 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 2024:
External revenues	$	879	$	509	$	148	$	157		$	—	$	—	$	1,693
Intersegment revenues	9		—		—		34			—		(43)		—
Net income (loss) attributable to Ameren common shareholders	128		61		6		79		(a)	(16)		—		258
Capital expenditures	638		132		59		175			2		(4)		1,002
Three Months 2023:
External revenues	$	933	$	540	$	152	$	135		$	—	$	—	$	1,760
Intersegment revenues	8		—		—		26			—		(34)		—
Net income (loss) attributable to Ameren common shareholders	102		66		11		72		(a)	(14)		—		237
Capital expenditures	433		180		90		197			2		(11)		891
Six Months 2024:
External revenues	$	1,647	$	1,015	$	539	$	308		$	—	$	—	$	3,509
Intersegment revenues	16		—		—		68			—		(84)		—
Net income (loss) attributable to Ameren common shareholders	153		117		112		151		(a)	(14)		—		519
Capital expenditures	1,104		316		119		341			4		8		1,892
Six Months 2023:
External revenues	$	1,846	$	1,164	$	543	$	269		$	—	$	—	$	3,822
Intersegment revenues	18		—		—		55			—		(73)		—
Net income attributable to Ameren common shareholders	130		127		98		143		(a)	3		—		501
Capital expenditures	914		350		141		410			5		2		1,822

(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 2024:
External revenues	$	509	$	148	$	109	$	—	$	766
Intersegment revenues	—		—		27		(27)		—
Net income available to common shareholder	61		6		57		—		124
Capital expenditures	132		59		153		—		344
Three Months 2023:
External revenues	$	540	$	152	$	87	$	—	$	779
Intersegment revenues	—		—		26		(26)		—
Net income available to common shareholder	66		11		52		—		129
Capital expenditures	180		90		167		—		437
Six Months 2024:
External revenues	$	1,015	$	539	$	212	$	—	$	1,766
Intersegment revenues	—		—		55		(55)		—
Net income available to common shareholder	117		112		110		—		339
Capital expenditures	316		119		282		—		717
Six Months 2023:
External revenues	$	1,164	$	543	$	173	$	—	$	1,880
Intersegment revenues	—		—		54		(54)		—
Net income available to common shareholder	127		98		102		—		327
Capital expenditures	350		141		353		—		844

The following tables present disaggregated revenues by segment at Ameren and Ameren Illinois for the three and six months ended June 30, 2024 and 2023. 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 2024:
Residential	$	395	$	311		$	—	$	—	$	—	$	706
Commercial	324		163			—		—		—		487
Industrial	77		47			—		—		—		124
Other	68		(12)		(a)	—		191		(43)		204
Total electric revenues	$	864	$	509		$	—	$	191	$	(43)	$	1,521
Residential	$	13	$	—		$	102	$	—	$	—	$	115
Commercial	5		—			24		—		—		29
Industrial	1		—			1		—		—		2
Other	5		—			21		—		—		26
Total natural gas revenues	$	24	$	—		$	148	$	—	$	—	$	172
Total revenues(b)	$	888	$	509		$	148	$	191	$	(43)	$	1,693


	Ameren Missouri		Ameren Illinois Electric Distribution			Ameren Illinois Natural Gas		Ameren Transmission		Intersegment Eliminations		Ameren
Three Months 2023:
Residential	$	360	$	337		$	—	$	—	$	—	$	697
Commercial	311		193			—		—		—		504
Industrial	75		48			—		—		—		123
Other	172		(38)		(a)	—		161		(34)		261
Total electric revenues	$	918	$	540		$	—	$	161	$	(34)	$	1,585
Residential	$	13	$	—		$	98	$	—	$	—	$	111
Commercial	6		—			25		—		—		31
Industrial	1		—			2		—		—		3
Other	3		—			27		—		—		30
Total natural gas revenues	$	23	$	—		$	152	$	—	$	—	$	175
Total revenues(b)	$	941	$	540		$	152	$	161	$	(34)	$	1,760
Six Months 2024:
Residential	$	736	$	608		$	—	$	—	$	—	$	1,344
Commercial	583		328			—		—		—		911
Industrial	138		92			—		—		—		230
Other	121		(13)		(a)	—		376		(84)		400
Total electric revenues	$	1,578	$	1,015		$	—	$	376	$	(84)	$	2,885
Residential	$	53	$	—		$	389	$	—	$	—	$	442
Commercial	21		—			92		—		—		113
Industrial	3		—			5		—		—		8
Other	8		—			53		—		—		61
Total natural gas revenues	$	85	$	—		$	539	$	—	$	—	$	624
Total revenues(b)	$	1,663	$	1,015		$	539	$	376	$	(84)	$	3,509
Six Months 2023:
Residential	$	684	$	719		$	—	$	—	$	—	$	1,403
Commercial	558		393			—		—		—		951
Industrial	136		96			—		—		—		232
Other	381		(44)		(a)	—		324		(72)		589
Total electric revenues	$	1,759	$	1,164		$	—	$	324	$	(72)	$	3,175
Residential	$	65	$	—		$	394	$	—	$	—	$	459
Commercial	29		—			102		—		—		131
Industrial	3		—			9		—		—		12
Other	8		—			38		—		(1)		45
Total natural gas revenues	$	105	$	—		$	543	$	—	$	(1)	$	647
Total revenues(b)	$	1,864	$	1,164		$	543	$	324	$	(73)	$	3,822

(a)Includes over-recoveries of various riders.

(b)The following table presents increases/(decreases) in revenues from alternative revenue programs and other revenues not from contracts with customers for the three and six months ended June 30, 2024 and 2023:


	Ameren Missouri			Ameren Illinois Electric Distribution		Ameren Illinois Natural Gas		Ameren Transmission		Ameren
Three Months 2024:
Revenues from alternative revenue programs	$	(1)		$	22	$	—	$	4	$	25
Other revenues not from contracts with customers	1			1		1		—		3
Three Months 2023:
Revenues from alternative revenue programs	$	—		$	60	$	9	$	5	$	74
Other revenues not from contracts with customers	(2)		(a)	2		1		—		1		(a)
Six Months 2024:
Revenues from alternative revenue programs	$	(7)		$	61	$	19	$	13	$	86
Other revenues not from contracts with customers	2			3		2		—		7
Six Months 2023:
Revenues from alternative revenue programs	$	(2)		$	124	$	37	$	13	$	172
Other revenues not from contracts with customers	(8)		(a)	4		2		—		(2)		(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 2024:
Residential	$	311		$	102	$	—	$	—	$	413
Commercial	163			24		—		—		187
Industrial	47			1		—		—		48
Other	(12)		(a)	21		136		(27)		118
Total revenues(b)	$	509		$	148	$	136	$	(27)	$	766
Three Months 2023:
Residential	$	337		$	98	$	—	$	—	$	435
Commercial	193			25		—		—		218
Industrial	48			2		—		—		50
Other	(38)		(a)	27		113		(26)		76
Total revenues(b)	$	540		$	152	$	113	$	(26)	$	779
Six Months 2024:
Residential	$	608		$	389	$	—	$	—	$	997
Commercial	328			92		—		—		420
Industrial	92			5		—		—		97
Other	(13)		(a)	53		267		(55)		252
Total revenues(b)	$	1,015		$	539	$	267	$	(55)	$	1,766
Six Months 2023:
Residential	$	719		$	394	$	—	$	—	$	1,113
Commercial	393			102		—		—		495
Industrial	96			9		—		—		105
Other	(44)		(a)	38		227		(54)		167
Total revenues(b)	$	1,164		$	543	$	227	$	(54)	$	1,880

(a)Includes over-recoveries of various riders.

(b)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 and six months ended June 30, 2024 and 2023:


	Ameren Illinois Electric Distribution		Ameren Illinois Natural Gas		Ameren Illinois Transmission		Ameren Illinois
Three Months 2024:
Revenues from alternative revenue programs	$	22	$	—	$	2	$	24
Other revenues not from contracts with customers	1		1		—		2
Three Months 2023:
Revenues from alternative revenue programs	$	60	$	9	$	3	$	72
Other revenues not from contracts with customers	2		1		—		3
Six Months 2024:
Revenues from alternative revenue programs	$	61	$	19	$	10	$	90
Other revenues not from contracts with customers	3		2		—		5
Six Months 2023:
Revenues from alternative revenue programs	$	124	$	37	$	10	$	171
Other revenues not from contracts with customers	4		2		—		6

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-22

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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-Paragraph 15
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-15

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

+ Details

Insider Trading Arrangements	3 Months Ended	6 Months Ended
Insider Trading Arrangements	Jun. 30, 2024 shares	Jun. 30, 2024 shares
Trading Arrangements, by Individual
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false
Michael L. Moehn [Member]
Trading Arrangements, by Individual
Material Terms of Trading Arrangement		On May 21, 2024, Michael L. Moehn, Senior Executive Vice President and Chief Financial Officer of Ameren, adopted a Rule 10b5-1 trading arrangement. Mr. Moehn's Rule 10b5-1 trading arrangement provides for the sale of an aggregate 26,000 shares to be sold in four equal quarterly installments between August 2024 and July 2025. Mr. Moehn’s' Rule 10b5-1 trading arrangement will terminate on the earlier of: (i) July 31, 2025; (ii) execution of all trades or expiration of all orders relating to such trades under the Rule 10b5-1 trading arrangement; or (iii) such date as the Rule 10b5-1 trading arrangement is otherwise terminated according to its terms.
Name	Michael L. Moehn
Title	Senior Executive Vice President and Chief Financial Officer of Ameren
Rule 10b5-1 Arrangement Adopted	true
Adoption Date	May 21, 2024
Arrangement Duration	436 days
Aggregate Available	26,000	26,000
Shawn E. Schukar [Member]
Trading Arrangements, by Individual
Material Terms of Trading Arrangement		On May 22, 2024, Shawn E. Schukar, Chairman and President of ATXI, adopted a Rule 10b5-1 trading arrangement. Mr. Schukar's Rule 10b5-1 trading arrangement provides for the sale of 100% of any net shares of Ameren common stock received, after tax withholding, in connection with certain previously awarded restricted stock units and performance share units that will vest upon payment in March 2025 and March 2026. The estimated maximum number of shares to be sold pursuant to the Rule 10b5-1 trading arrangement is 10,170 shares. The actual number of shares sold pursuant to the Rule 10b5-1 trading arrangement will depend on the actual number of shares earned pursuant to the awards, which is generally dependent on the Company's achievement of certain performance measures, the actual dividends paid by the Company during the applicable vesting periods, and Mr. Schukar's continued employment and individual performance during the applicable vesting periods. Mr. Schukar's Rule 10b5-1 trading arrangement will terminate on the earlier of: (i) March 31, 2026; (ii) execution of all trades or expiration of all orders relating to such trades under the Rule 10b5-1 trading arrangement; or (iii) such date as the Rule 10b5-1 trading arrangement is otherwise terminated according to its terms.
Name	Shawn E. Schukar
Title	Chairman and President of ATXI
Rule 10b5-1 Arrangement Adopted	true
Adoption Date	May 22, 2024
Arrangement Duration	678 days
Aggregate Available	10,170	10,170
Mark C. Lindgren [Member]
Trading Arrangements, by Individual
Material Terms of Trading Arrangement		On June 6, 2024, Mark C. Lindgren, Executive Vice President, Corporate Communications, and Chief Human Resources Officer of Ameren Services Company, adopted a Rule 10b5-1 trading arrangement. Mr. Lindgren's Rule 10b5-1 trading arrangement provides for the sale of 50% of any net shares of Ameren common stock received, after tax withholding, in connection with certain previously awarded restricted stock units and performance share units that will vest upon payment in March 2025 and March 2026. The estimated maximum number of shares to be sold pursuant to the Rule 10b5-1 trading arrangement is 3,841 shares. The actual number of shares sold pursuant to the Rule 10b5-1 trading arrangement will depend on the actual number of shares earned pursuant to the awards, which is generally dependent on the Company's achievement of certain performance measures, the actual dividends paid by the Company during the applicable vesting periods, and Mr. Lindgren's continued employment and individual performance during the applicable vesting periods. Mr. Lindgren's Rule 10b5-1 trading arrangement will terminate on the earlier of: (i) March 31, 2026; (ii) execution of all trades or expiration of all orders relating to such trades under the Rule 10b5-1 trading arrangement; or (iii) such date as the Rule 10b5-1 trading arrangement is otherwise terminated according to its terms.
Name	Mark C. Lindgren
Title	Executive Vice President, Corporate Communications, and Chief Human Resources Officer of Ameren Services Company
Rule 10b5-1 Arrangement Adopted	true
Adoption Date	June 6, 2024
Arrangement Duration	663 days
Aggregate Available	3,841	3,841

Summary Of Significant Accounting Policies (Policies)	6 Months Ended
Summary Of Significant Accounting Policies (Policies)	Jun. 30, 2024
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 also 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 statement of our results. The preparation of financial statements in conformity with GAAP requires management to make certain estimates and assumptions. Such estimates and assumptions affect reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the dates of financial statements, and the reported amounts of revenues and expenses during the 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 June 30, 2024, and December 31, 2023, Ameren had unconsolidated variable interests in various equity method investments, primarily to advance clean and resilient energy technologies, totaling $75 million and $73 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 June 30, 2024, Ameren’s maximum exposure to loss related to these variable interests is limited to its investment of $75 million plus associated outstanding funding commitments of $12 million.
Life Insurance, Corporate Or Bank Owned	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.
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 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. 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.
Deferred Compensation	Deferred Compensation At June 30, 2024, and December 31, 2023, the present value of benefits to be paid for deferred compensation obligations was $80 million and $85 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 June 30, 2024 and 2023, 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 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.

- Definition

Disclosure of accounting policy for revenue from contract with customer.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
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-Name Accounting Standards Codification
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-URI https://asc.fasb.org//1943274/2147479806/606-10-50-17

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Rate and Regulatory Matters (Tables)

6 Months Ended

Jun. 30, 2024

Regulated Operations [Abstract]

Schedule of Generation Facilities

The following table provides information with respect to each agreement:

Agreement type

Facility size

Status of MoPSC CCN

Status of FERC approval of acquisition

Anticipated in-service date(a)

Huck Finn Solar Project(b)(c)

Build-transfer

200-MW

Approved February 2023

Received March 2023

Fourth quarter 2024

Boomtown Solar Project(c)(d)

Build-transfer

150-MW

Approved April 2023

Received October 2023

Fourth quarter 2024(e)

Cass County Solar Project(d)

Development-transfer(f)

150-MW

Approved June 2024

Not applicable

Fourth quarter 2024

Vandalia Solar Project(c)(g)

Self-build

50-MW

Approved March 2024

Not applicable

Fourth quarter 2025

Bowling Green Solar Project(c)(g)

Self-build

50-MW

Approved March 2024

Not applicable

First quarter 2026

Split Rail Solar Project(g)

Build-transfer

300-MW

Approved March 2024

Requested July 2024

Mid-2026

Castle Bluff Natural Gas Project

Self-build

800-MW

Filed June 2024

Not applicable

Fourth quarter 2027

(a)Anticipated in-service dates are dependent on the timing of regulatory approvals and construction completion, among other things.

(b)The Huck Finn Solar Project is expected to support Ameren Missouri’s compliance with the state of Missouri’s renewable energy standard. Investments in the project will be eligible for recovery under the RESRAM. Ameren Missouri expects to close on the acquisition of the Huck Finn Solar Project in the fourth quarter of 2024.

(c)These projects collectively represent approximately $0.85 billion of expected capital expenditures.

(d)The Boomtown and Cass County solar projects are expected to support Ameren Missouri’s transition to renewable energy generation and serve customers under the Renewable Solutions Program.

(e)Ameren Missouri expects to close on the acquisition of the Boomtown Solar Project in August 2024.

(f)In June 2024, Ameren Missouri acquired the Cass County Solar Project, which includes solar panels, project design, land rights, and engineering, procurement, and construction agreements, for approximately $250 million and took over construction management of the project.

(g)These solar projects are expected to support Ameren Missouri’s transition to renewable energy generation.

Schedule of MYRP details

The following table presents the approved revenue requirements and average annual rate base in the ICC’s June 2024 rehearing order, as well as the proposed revenue requirements and average annual rate base in Ameren Illinois’ July 2024 revised MYRP and the ICC staff’s July 2024 revised MYRP recommendation:


Year	Revenue Requirement (in millions)	Average Annual Rate Base (in billions)
ICC’s June 2024 Rehearing Order(a):
2024	$1,196	$4.0
2025	$1,282	$4.3
2026	$1,350	$4.5
2027	$1,397	$4.7
Ameren Illinois’ July 2024 Revised MYRP(a):
2024	$1,215	$4.3
2025	$1,300	$4.5
2026	$1,386	$4.8
2027	$1,446	$5.0
ICC Staff’s July 2024 Revised MYRP(a):
2024	$1,201	$4.2
2025	$1,281	$4.4
2026	$1,361	$4.6
2027	$1,414	$4.8

(a)Based on an allowed ROE of 8.72% and a capital structure composed of 50% common equity. The ROE is under appeal, as discussed above.

Short-Term Debt and Liquidity (Tables)

6 Months Ended

Jun. 30, 2024

Debt Disclosure [Abstract]

Schedule of Short-term Debt

The following table presents commercial paper outstanding, net of issuance discounts, as of June 30, 2024, and December 31, 2023. There were no borrowings outstanding under the Credit Agreements as of June 30, 2024, or December 31, 2023.


	June 30, 2024		December 31, 2023
Ameren (parent)	$	301	$	—
Ameren Missouri	390		170
Ameren Illinois	—		366
Ameren consolidated	$	691	$	536

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 six months ended June 30, 2024 and 2023:


	Ameren (parent)			Ameren Missouri			Ameren Illinois			Ameren Consolidated
2024
Average daily amount outstanding	$	84		$	109		$	385		$	578

Weighted-average interest rate	5.55		%	5.53		%	5.57		%	5.56		%
Peak amount outstanding during period(a)	$	301		$	509		$	694		$	1,084
Peak interest rate	5.60		%	5.68		%	5.68		%	5.68		%
2023
Average daily amount outstanding	$	595		$	343		$	230		$	1,168

Weighted-average interest rate	5.14		%	5.04		%	5.10		%	5.10		%
Peak amount outstanding during period(a)	$	841		$	592		$	450		$	1,381
Peak interest rate	5.55		%	5.55		%	5.60		%	5.60		%

(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 amount for the period.

Other Income, Net (Tables)

6 Months Ended

Jun. 30, 2024

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 and six months ended June 30, 2024 and 2023:


	Three Months				Six Months
	2024		2023		2024		2023
Ameren:

Allowance for equity funds used during construction	$	16	$	14	$	25	$	23
Other interest income	13		9		21		17

Non-service cost components of net periodic benefit income(a)	76		63		152		127
Miscellaneous income	4		2		6		4
Earnings related to equity method investments	1		—		1		2
Donations	(2)		(2)		(4)		(4)
Miscellaneous expense	(5)		(4)		(9)		(9)
Total Other Income, Net	$	103	$	82	$	192	$	160
Ameren Missouri:

Allowance for equity funds used during construction	$	14	$	8	$	23	$	12
Other interest income	3		2		5		6
Non-service cost components of net periodic benefit income(a)	35		14		69		28
Miscellaneous income	—		1		2		2
Donations	(1)		(1)		(2)		(2)
Miscellaneous expense	(2)		(2)		(4)		(5)
Total Other Income, Net	$	49	$	22	$	93	$	41
Ameren Illinois:

Allowance for equity funds used during construction	$	2	$	6	$	2	$	10
Other interest income	9		6		15		10

Non-service cost components of net periodic benefit income	26		31		53		62
Miscellaneous income	2		1		3		2
Donations	(1)		(1)		(2)		(2)
Miscellaneous expense	(1)		(2)		(3)		(4)
Total Other Income, Net	$	37	$	41	$	68	$	78

(a)For the three and six months ended June 30, 2024, the non-service cost components of net periodic benefit income were adjusted by amounts deferred of $(11) million and $(20) 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. The deferral was $17 million and $34 million, respectively, for the three and six months ended June 30, 2023. See Note 11 – Retirement Benefits for additional information.

Derivative Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2024

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 June 30, 2024, and December 31, 2023. As of June 30, 2024, these contracts extended through October 2027, October 2029 and May 2032 for fuel oils, natural gas and power, respectively.


	Quantity (in millions)
	June 30, 2024			December 31, 2023
Commodity	Ameren Missouri	Ameren Illinois	Ameren	Ameren Missouri	Ameren Illinois	Ameren
Fuel oils (in gallons)	20	—	20	17	—	17
Natural gas (in mmbtu)	52	221	273	53	218	271
Power (in MWhs)	—	5	5	—	5	5
Uranium (pounds in thousands)	—	—	—	186	—	186

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 June 30, 2024, and December 31, 2023:


		June 30, 2024						December 31, 2023
	Balance Sheet Location	Ameren Missouri		Ameren Illinois		Ameren			Ameren Missouri		Ameren Illinois		Ameren







Fuel oils	Other current assets	$	2	$	—	$	2		$	2	$	—	$	2



Natural gas	Other current assets	1		3		4			—		—		—
	Other assets	2		1		3			3		3		6


Power	Other current assets	15		—		15			5		—		5



Uranium	Other current assets	—		—		—			9		—		9

	Total assets	$	20	$	4	$	24		$	19	$	3	$	22


Fuel oils	Other current liabilities	$	1	$	—	$	1		$	1	$	—	$	1
	Other deferred credits and liabilities	—		—		—			1		—		1


Natural gas	Other current liabilities	9		33		42			12		45		57
	Other deferred credits and liabilities	8		28		36			10		30		40


Power	Other current liabilities	1		11		12			1		12		13
	Other deferred credits and liabilities	—		50		50			—		56		56




	Total liabilities	$	19	$	122	$	141		$	25	$	143	$	168

Offsetting Assets and Liabilities

The following table provides the recognized gross derivative balances and the net amounts of those derivatives subject to an enforceable master netting arrangement or similar agreement as of June 30, 2024, and December 31, 2023:


			Gross Amounts Not Offset in the Balance Sheet
Commodity Contracts Eligible to be Offset	Gross Amounts Recognized in the Balance Sheet		Derivative Instruments		Cash Collateral Received/Posted(a)		Net Amount
June 30, 2024
Assets:
Ameren Missouri	$	20	$	5	$	—	$	15
Ameren Illinois	4		2		—		2
Ameren	$	24	$	7	$	—	$	17
Liabilities:
Ameren Missouri	$	19	$	5	$	—	$	14
Ameren Illinois	122		2		—		120
Ameren	$	141	$	7	$	—	$	134
December 31, 2023
Assets:
Ameren Missouri	$	19	$	6	$	—	$	13
Ameren Illinois	3		1		—		2
Ameren	$	22	$	7	$	—	$	15
Liabilities:
Ameren Missouri	$	25	$	6	$	—	$	19
Ameren Illinois	143		1		6		136
Ameren	$	168	$	7	$	6	$	155

(a)Cash collateral received reduces gross asset balances and is included in “Other current liabilities” and “Other deferred credits and liabilities” on the balance sheet. Cash collateral posted reduces gross liability balances and is included in “Other current assets” and “Other assets” on the balance sheet.

Derivative Instruments With Credit Risk-Related Contingent Features

The following table presents, as of June 30, 2024, 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 Collateral Posted		Potential Aggregate Amount of Additional Collateral Required(b)
Ameren Missouri	$	19	$	—	$	13
Ameren Illinois	61		—		59
Ameren	$	80	$	—	$	72

(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)

6 Months Ended

Jun. 30, 2024

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 June 30, 2024, and December 31, 2023:


		June 30, 2024									December 31, 2023
		Level 1		Level 2		Level 3		Total			Level 1		Level 2		Level 3		Total
Assets:
Ameren Missouri
	Derivative assets – commodity contracts:
	Fuel oils	$	1	$	—	$	1	$	2		$	2	$	—	$	—	$	2
	Natural gas	—		3		—		3			—		3		—		3
	Power	—		—		15		15			—		—		5		5
	Uranium	—		—		—		—			—		—		9		9
	Total derivative assets – commodity contracts	$	1	$	3	$	16	$	20		$	2	$	3	$	14	$	19
	Nuclear decommissioning trust fund:

	Equity securities:
	U.S. large capitalization	$	842	$	—	$	—	$	842		$	787	$	—	$	—	$	787
	Debt securities:
	U.S. Treasury and agency securities	—		178		—		178			—		150		—		150
	Corporate bonds	—		154		—		154			—		136		—		136


	Other	—		82		—		82			—		68		—		68
	Total nuclear decommissioning trust fund	$	842	$	414	$	—	$	1,256	(a)	$	787	$	354	$	—	$	1,141	(a)
	Total Ameren Missouri	$	843	$	417	$	16	$	1,276		$	789	$	357	$	14	$	1,160
Ameren Illinois
	Derivative assets – commodity contracts:
	Natural gas	—		1		3		4			—		1		2		3

	Total Ameren Illinois	$	—	$	1	$	3	$	4		$	—	$	1	$	2	$	3
Ameren
	Derivative assets – commodity contracts(b)	$	1	$	4	$	19	$	24		$	2	$	4	$	16	$	22
	Nuclear decommissioning trust fund(c)	842		414		—		1,256		(a)	787		354		—		1,141		(a)
	Total Ameren	$	843	$	418	$	19	$	1,280		$	789	$	358	$	16	$	1,163
Liabilities:
Ameren Missouri
	Derivative liabilities – commodity contracts:
	Fuel oils	$	1	$	—	$	—	$	1		$	2	$	—	$	—	$	2
	Natural gas	—		16		1		17			—		19		3		22
	Power	—		—		1		1			—		—		1		1

	Total Ameren Missouri	$	1	$	16	$	2	$	19		$	2	$	19	$	4	$	25
Ameren Illinois
	Derivative liabilities – commodity contracts:
	Natural gas	$	2	$	52	$	7	$	61		$	4	$	60	$	11	$	75
	Power	—		—		61		61			—		—		68		68
	Total Ameren Illinois	$	2	$	52	$	68	$	122		$	4	$	60	$	79	$	143
Ameren
	Derivative liabilities – commodity contracts(b)	$	3	$	68	$	70	$	141		$	6	$	79	$	83	$	168

(a)Balance excludes $10 million and $9 million of cash and cash equivalents, receivables, payables, and accrued income, net, for June 30, 2024, and December 31, 2023, 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 and six months ended June 30, 2024 and 2023:


	2024						2023
	Ameren Missouri		Ameren Illinois		Ameren			Ameren Missouri		Ameren Illinois		Ameren
For the three months ended June 30:
Beginning balance at April 1	$	2	$	(54)	$	(52)		$	5	$	(52)	$	(47)
Realized and unrealized gains/(losses) included in regulatory assets/liabilities	15		(12)		3			14		(20)		(6)


Settlements	(3)		5		2			(5)		4		(1)


Ending balance at June 30	$	14	$	(61)	$	(47)		$	14	$	(68)	$	(54)
Change in unrealized gains/(losses) related to assets/liabilities held at June 30	$	14	$	(12)	$	2		$	14	$	(20)	$	(6)
For the six months ended June 30:
Beginning balance at January 1	$	4	$	(68)	$	(64)		$	12	$	(33)	$	(21)
Realized and unrealized gains/(losses) included in regulatory assets/liabilities	14		(2)		12			8		(41)		(33)


Settlements	(4)		9		5			(6)		6		—


Ending balance at June 30	$	14	$	(61)	$	(47)		$	14	$	(68)	$	(54)
Change in unrealized gains/(losses) related to assets/liabilities held at June 30	$	14	$	—	$	14		$	14	$	(35)	$	(21)

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 June 30, 2024, and December 31, 2023:


			Fair Value						Weighted Average(b)
	Commodity		Assets		Liabilities	Valuation Technique(s)	Unobservable Input(a)	Range
2024	Power(c)	$	15	$	(62)	Discounted cash flow	Average forward peak and off-peak pricing – forwards/swaps ($/MWh)	33 – 70	43

							Nodal basis ($/MWh)	(10) – (1)	(5)


2023	Power(c)	$	5	$	(69)	Discounted cash flow	Average forward peak and off-peak pricing – forwards/swaps ($/MWh)	31 – 65	43

							Nodal basis ($/MWh)	(8) – (1)	(5)

(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.

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 long-term debt (including current portion) disclosed, but not recorded, at fair value as of June 30, 2024, and December 31, 2023:


Long-Term Debt (Including Current Portion):	Carrying Amount(a)		Fair Value
			Level 2		Level 3			Total
	June 30, 2024




Ameren	$	17,079	$	14,990	$	460	(b)	$	15,450






Ameren Missouri	6,830		6,069		—			6,069





Ameren Illinois	5,851		5,251		—			5,251
	December 31, 2023



Ameren	$	15,970	$	14,366	$	467	(b)	$	14,833






Ameren Missouri	6,341		5,800		—			5,800




Ameren Illinois	5,232		4,867		—			4,867

(a)Included unamortized debt issuance costs, which were excluded from the fair value measurement, of $124 million, $53 million, and $52 million for Ameren, Ameren Missouri, and Ameren Illinois, respectively, as of June 30, 2024. Included unamortized debt issuance costs, which were excluded from the fair value measurement, of $111 million, $45 million, and $47 million for Ameren, Ameren Missouri, and Ameren Illinois, respectively, as of December 31, 2023.

(b)The Level 3 fair value amount consists of ATXI’s senior unsecured notes.

Related Party Transactions (Tables)

6 Months Ended

Jun. 30, 2024

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 June 30, 2024, and December 31, 2023:


	June 30, 2024				December 31, 2023
	Ameren Missouri		Ameren Illinois		Ameren Missouri		Ameren Illinois
Income taxes payable to parent(a)	$	—	$	44	$	—	$	2
Income taxes receivable from parent(b)	54		—		56		22

(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 and six months ended June 30, 2024 and 2023:


				Three Months				Six Months
Agreement	Income Statement Line Item			Ameren Missouri		Ameren Illinois		Ameren Missouri		Ameren Illinois
Ameren Missouri power supply	Operating Revenues	2024	$	(b)	$	(a)	$	(b)	$	(a)
agreements with Ameren Illinois		2023		(b)		(a)		(b)		(a)
Ameren Missouri and Ameren Illinois	Operating Revenues	2024	$	8	$	(b)	$	15	$	(b)
rent and facility services		2023		8		(b)		18		(b)
Ameren Missouri and Ameren Illinois miscellaneous	Operating Revenues	2024	$	1	$	(b)	$	1	$	1
support services		2023		(b)		(b)		(b)		(b)
Total Operating Revenues		2024	$	9	$	(b)	$	16	$	1
		2023		8		(b)		18		(b)
Ameren Illinois power supply	Purchased Power	2024	$	(a)	$	(b)	$	(a)	$	(b)
agreements with Ameren Missouri		2023		(a)		(b)		(a)		(b)
Ameren Missouri and Ameren Illinois	Purchased Power	2024	$	2	$	1	$	4	$	1
transmission services from ATXI		2023		1		(b)		1		(b)
Total Purchased Power		2024	$	2	$	1	$	4	$	1
		2023		1		(b)		1		(b)
Ameren Missouri and Ameren Illinois	Other Operations and Maintenance	2024	$	(b)	$	(b)	$	(b)	$	(b)
rent and facility services		2023		(b)		(b)		(b)		2
Ameren Services support services	Other Operations and Maintenance	2024	$	43	$	40	$	81	$	77
agreement		2023		35		33		70		68
Total Other Operations and		2024	$	43	$	40	$	81	$	77
Maintenance		2023		35		33		70		70
Money pool interest	(Interest Charges)/Other Income, Net	2024	$	(b)	$	(b)	$	(3)	$	(2)
		2023		(b)		(b)		(b)		(b)

(a)Not applicable.

(b)Amount less than $1 million.

Callaway Energy Center (Tables)

6 Months Ended

Jun. 30, 2024

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, 2024:


Type and Source of Coverage	Most Recent Renewal Date	Maximum Coverages			Maximum Assessments for Single Incidents
Public liability and nuclear worker liability:
American Nuclear Insurers	January 1, 2024	$	500		$	—
Pool participation	(a)	15,763		(a)	166		(b)
		$	16,263	(c)	$	166
Property damage:
NEIL and EMANI	April 1, 2024	$	3,200	(d)	$	28	(e)
Accidental outage:
NEIL	April 1, 2024	$	490	(f)	$	11	(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 $500 million in the event of an incident at any licensed United States commercial reactor, payable at $24.7 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 $0.7 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 $291 million.

Retirement Benefits (Tables)

6 Months Ended

Jun. 30, 2024

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 and six months ended June 30, 2024 and 2023:


	Pension Benefits								Postretirement Benefits
	Three Months				Six Months				Three Months				Six Months
	2024		2023		2024		2023		2024		2023		2024		2023
Service cost(a)	$	23	$	23	$	44	$	46	$	3	$	3	$	6	$	6
Non-service cost components:
Interest cost	56		56		111		111		11		12		22		23
Expected return on plan assets(b)	(82)		(84)		(164)		(167)		(23)		(23)		(46)		(46)
Amortization of(b):

Prior service benefit	—		—		—		—		(1)		(1)		(2)		(2)
Actuarial (gain)	(16)		(28)		(33)		(57)		(10)		(12)		(20)		(23)
Total non-service cost components(c)	$	(42)	$	(56)	$	(86)	$	(113)	$	(23)	$	(24)	$	(46)	$	(48)

Net periodic benefit income(d)	$	(19)	$	(33)	$	(42)	$	(67)	$	(20)	$	(21)	$	(40)	$	(42)

(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 and six months ended June 30, 2024 and 2023:


	Pension Benefits								Postretirement Benefits
	Three Months				Six Months				Three Months				Six Months
	2024		2023		2024		2023		2024		2023		2024		2023
Ameren Missouri(a)	$	(10)	$	(17)	$	(22)	$	(35)	$	(7)	$	(7)	$	(14)	$	(15)
Ameren Illinois	(8)		(13)		(17)		(27)		(13)		(14)		(26)		(27)
Other	(1)		(3)		(3)		(5)		—		—		—		—
Ameren(a)	$	(19)	$	(33)	$	(42)	$	(67)	$	(20)	$	(21)	$	(40)	$	(42)

(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 (Tables)

6 Months Ended

Jun. 30, 2024

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 and six months ended June 30, 2024 and 2023:


	Ameren				Ameren Missouri				Ameren Illinois
	2024		2023		2024		2023		2024		2023
Three Months
Federal statutory corporate income tax rate	21	%	21	%	21	%	21	%	21	%	21	%
Increases (decreases) from:
Amortization of excess deferred taxes(a)	(8)		(7)		(14)		(15)		(4)		(2)

Renewable and other tax credits(b)	(4)		(5)		(8)		(10)		—		—
State tax	5		5		3		3		7		7
Depreciation differences	(1)		—		(1)		—		—		(1)



Effective income tax rate	13	%	14	%	1	%	(1)	%	24	%	25	%
Six Months
Federal statutory corporate income tax rate	21	%	21	%	21	%	21	%	21	%	21	%
Increases (decreases) from:

Amortization of excess deferred taxes(a)	(8)		(8)		(14)		(15)		(4)		(2)

Renewable and other tax credits(b)	(4)		(4)		(8)		(10)		—		—
State tax	5		5		3		3		7		7

Depreciation differences	—		—		—		—		—		(1)
Other permanent items	—		(1)		—		—		—		—
Effective income tax rate	14	%	13	%	2	%	(1)	%	24	%	25	%

(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 (Tables)

6 Months Ended

Jun. 30, 2024

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 June 30, 2024, and December 31, 2023:


	June 30, 2024						December 31, 2023
	Ameren		Ameren Missouri		Ameren Illinois		Ameren		Ameren Missouri		Ameren Illinois
“Cash and cash equivalents”	$	19	$	—	$	6	$	25	$	—	$	—

Restricted cash included in “Other current assets”	18		7		7		13		5		5
Restricted cash included in “Other assets”	260		—		260		229		—		229
Restricted cash included in “Nuclear decommissioning trust fund”	4		4		—		5		5		—
Total cash, cash equivalents, and restricted cash	$	301	$	11	$	273	$	272	$	10	$	234

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 and six months ended June 30, 2024 and 2023:


	Three Months				Six Months
	2024		2023		2024		2023
Ameren:
Beginning of period	$	37	$	34	$	30	$	31
Bad debt expense	6		13		16		23
Charged to other accounts(a)	1		1		4		1
Net write-offs	(7)		(9)		(13)		(16)
End of period	$	37	$	39	$	37	$	39
Ameren Missouri:
Beginning of period	$	11	$	12	$	12	$	13
Bad debt expense	4		2		5		4
Net write-offs	(3)		(2)		(5)		(5)
End of period	$	12	$	12	$	12	$	12
Ameren Illinois:(b)
Beginning of period	$	26	$	22	$	18	$	18
Bad debt expense	2		11		11		19
Charged to other accounts(a)	1		1		4		1
Net write-offs	(4)		(7)		(8)		(11)
End of period	$	25	$	27	$	25	$	27

(a)Amounts associated with the allowance for doubtful accounts related to receivables purchased by Ameren Illinois from alternative retail electric suppliers, as required by the Illinois Public Utilities Act.

(b)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. The table above does not include the impact related to the riders.

Schedule of Cash Flow, Supplemental Disclosures

The following table provides noncash financing and investing activity excluded from the statements of cash flows for the six months ended June 30, 2024 and 2023:


	June 30, 2024						June 30, 2023
	Ameren		Ameren Missouri				Ameren Illinois	Ameren		Ameren Missouri		Ameren Illinois
Investing:
Accrued capital expenditures, including nuclear fuel expenditures	$	380	$	232	$	134		$	325	$	132	$	173

Net realized and unrealized gain – nuclear decommissioning trust fund	103		103		—			105		105		—
Return of investment in industrial development revenue bonds(a)	—		—		—			240		240		—
Financing:
Issuance of common stock for stock-based compensation	$	16	$	—	$	—		$	37	$	—	$	—
Issuance of common stock under the DRPlus	7		—		—			7		—		—
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 six months ended June 30, 2024:


	Ameren Missouri			Ameren Illinois			Ameren
Balance at December 31, 2023	$	787	(a)	$	4	(b)	$	791	(a)
Liabilities incurred	7		(c)	—			7		(c)
Liabilities settled	(4)			(1)			(5)
Accretion	17		(d)	—			17		(d)

Balance at June 30, 2024	$	807	(a)	$	3	(b)	$	810	(a)

(a)Balance included $19 million in “Other current liabilities” on the balance sheet as of both June 30, 2024, and December 31, 2023.

(b)Included in “Other deferred credits and liabilities” on the balance sheet.

(c)In June 2024, Ameren and Ameren Missouri recorded an ARO related to the decommissioning for the Cass County Solar Project. In addition, as a result of the 2024 CCR Rule, Ameren and Ameren Missouri recorded an immaterial increase to their AROs associated with CCR storage facilities. See Note 9 – Commitments and Contingencies for additional information.

(d)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 and six months ended June 30, 2024 and 2023:


	Three Months				Six Months
	2024		2023		2024		2023
Ameren Missouri	$	41	$	39	$	76	$	73
Ameren Illinois	28		26		65		63
Ameren	$	69	$	65	$	141	$	136

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 and six months ended June 30, 2024 and 2023:


	Three Months		Six Months
	2024	2023	2024	2023


Weighted-average Common Shares Outstanding – Basic	266.7	262.6	266.5	262.4
Assumed settlement of performance share units and restricted stock units	0.1	0.6	0.3	0.8

Weighted-average Common Shares Outstanding – Diluted(a)	266.8	263.2	266.8	263.2

(a)There was an immaterial number of anti-dilutive performance share units excluded from the earnings per diluted share calculations for the three and six months ended June 30, 2024 and 2023. The outstanding forward sale agreements as of June 30, 2024 and 2023, were anti-dilutive for the three and six months ended June 30, 2024 and 2023, and were excluded from the earnings per diluted share calculation as calculated using the treasury stock method. For additional information about the outstanding forward sale agreements, see Note 4 – Long-term Debt and Equity Financings.

Segment Information (Tables)

6 Months Ended

Jun. 30, 2024

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 and six months ended June 30, 2024 and 2023. 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 2024:
External revenues	$	879	$	509	$	148	$	157		$	—	$	—	$	1,693
Intersegment revenues	9		—		—		34			—		(43)		—
Net income (loss) attributable to Ameren common shareholders	128		61		6		79		(a)	(16)		—		258
Capital expenditures	638		132		59		175			2		(4)		1,002
Three Months 2023:
External revenues	$	933	$	540	$	152	$	135		$	—	$	—	$	1,760
Intersegment revenues	8		—		—		26			—		(34)		—
Net income (loss) attributable to Ameren common shareholders	102		66		11		72		(a)	(14)		—		237
Capital expenditures	433		180		90		197			2		(11)		891
Six Months 2024:
External revenues	$	1,647	$	1,015	$	539	$	308		$	—	$	—	$	3,509
Intersegment revenues	16		—		—		68			—		(84)		—
Net income (loss) attributable to Ameren common shareholders	153		117		112		151		(a)	(14)		—		519
Capital expenditures	1,104		316		119		341			4		8		1,892
Six Months 2023:
External revenues	$	1,846	$	1,164	$	543	$	269		$	—	$	—	$	3,822
Intersegment revenues	18		—		—		55			—		(73)		—
Net income attributable to Ameren common shareholders	130		127		98		143		(a)	3		—		501
Capital expenditures	914		350		141		410			5		2		1,822

(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 2024:
External revenues	$	509	$	148	$	109	$	—	$	766
Intersegment revenues	—		—		27		(27)		—
Net income available to common shareholder	61		6		57		—		124
Capital expenditures	132		59		153		—		344
Three Months 2023:
External revenues	$	540	$	152	$	87	$	—	$	779
Intersegment revenues	—		—		26		(26)		—
Net income available to common shareholder	66		11		52		—		129
Capital expenditures	180		90		167		—		437
Six Months 2024:
External revenues	$	1,015	$	539	$	212	$	—	$	1,766
Intersegment revenues	—		—		55		(55)		—
Net income available to common shareholder	117		112		110		—		339
Capital expenditures	316		119		282		—		717
Six Months 2023:
External revenues	$	1,164	$	543	$	173	$	—	$	1,880
Intersegment revenues	—		—		54		(54)		—
Net income available to common shareholder	127		98		102		—		327
Capital expenditures	350		141		353		—		844

Disaggregation of Revenue

The following tables present disaggregated revenues by segment at Ameren and Ameren Illinois for the three and six months ended June 30, 2024 and 2023. 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 2024:
Residential	$	395	$	311		$	—	$	—	$	—	$	706
Commercial	324		163			—		—		—		487
Industrial	77		47			—		—		—		124
Other	68		(12)		(a)	—		191		(43)		204
Total electric revenues	$	864	$	509		$	—	$	191	$	(43)	$	1,521
Residential	$	13	$	—		$	102	$	—	$	—	$	115
Commercial	5		—			24		—		—		29
Industrial	1		—			1		—		—		2
Other	5		—			21		—		—		26
Total natural gas revenues	$	24	$	—		$	148	$	—	$	—	$	172
Total revenues(b)	$	888	$	509		$	148	$	191	$	(43)	$	1,693


	Ameren Missouri		Ameren Illinois Electric Distribution			Ameren Illinois Natural Gas		Ameren Transmission		Intersegment Eliminations		Ameren
Three Months 2023:
Residential	$	360	$	337		$	—	$	—	$	—	$	697
Commercial	311		193			—		—		—		504
Industrial	75		48			—		—		—		123
Other	172		(38)		(a)	—		161		(34)		261
Total electric revenues	$	918	$	540		$	—	$	161	$	(34)	$	1,585
Residential	$	13	$	—		$	98	$	—	$	—	$	111
Commercial	6		—			25		—		—		31
Industrial	1		—			2		—		—		3
Other	3		—			27		—		—		30
Total natural gas revenues	$	23	$	—		$	152	$	—	$	—	$	175
Total revenues(b)	$	941	$	540		$	152	$	161	$	(34)	$	1,760
Six Months 2024:
Residential	$	736	$	608		$	—	$	—	$	—	$	1,344
Commercial	583		328			—		—		—		911
Industrial	138		92			—		—		—		230
Other	121		(13)		(a)	—		376		(84)		400
Total electric revenues	$	1,578	$	1,015		$	—	$	376	$	(84)	$	2,885
Residential	$	53	$	—		$	389	$	—	$	—	$	442
Commercial	21		—			92		—		—		113
Industrial	3		—			5		—		—		8
Other	8		—			53		—		—		61
Total natural gas revenues	$	85	$	—		$	539	$	—	$	—	$	624
Total revenues(b)	$	1,663	$	1,015		$	539	$	376	$	(84)	$	3,509
Six Months 2023:
Residential	$	684	$	719		$	—	$	—	$	—	$	1,403
Commercial	558		393			—		—		—		951
Industrial	136		96			—		—		—		232
Other	381		(44)		(a)	—		324		(72)		589
Total electric revenues	$	1,759	$	1,164		$	—	$	324	$	(72)	$	3,175
Residential	$	65	$	—		$	394	$	—	$	—	$	459
Commercial	29		—			102		—		—		131
Industrial	3		—			9		—		—		12
Other	8		—			38		—		(1)		45
Total natural gas revenues	$	105	$	—		$	543	$	—	$	(1)	$	647
Total revenues(b)	$	1,864	$	1,164		$	543	$	324	$	(73)	$	3,822

(a)Includes over-recoveries of various riders.

(b)The following table presents increases/(decreases) in revenues from alternative revenue programs and other revenues not from contracts with customers for the three and six months ended June 30, 2024 and 2023:


	Ameren Missouri			Ameren Illinois Electric Distribution		Ameren Illinois Natural Gas		Ameren Transmission		Ameren
Three Months 2024:
Revenues from alternative revenue programs	$	(1)		$	22	$	—	$	4	$	25
Other revenues not from contracts with customers	1			1		1		—		3
Three Months 2023:
Revenues from alternative revenue programs	$	—		$	60	$	9	$	5	$	74
Other revenues not from contracts with customers	(2)		(a)	2		1		—		1		(a)
Six Months 2024:
Revenues from alternative revenue programs	$	(7)		$	61	$	19	$	13	$	86
Other revenues not from contracts with customers	2			3		2		—		7
Six Months 2023:
Revenues from alternative revenue programs	$	(2)		$	124	$	37	$	13	$	172
Other revenues not from contracts with customers	(8)		(a)	4		2		—		(2)		(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 2024:
Residential	$	311		$	102	$	—	$	—	$	413
Commercial	163			24		—		—		187
Industrial	47			1		—		—		48
Other	(12)		(a)	21		136		(27)		118
Total revenues(b)	$	509		$	148	$	136	$	(27)	$	766
Three Months 2023:
Residential	$	337		$	98	$	—	$	—	$	435
Commercial	193			25		—		—		218
Industrial	48			2		—		—		50
Other	(38)		(a)	27		113		(26)		76
Total revenues(b)	$	540		$	152	$	113	$	(26)	$	779
Six Months 2024:
Residential	$	608		$	389	$	—	$	—	$	997
Commercial	328			92		—		—		420
Industrial	92			5		—		—		97
Other	(13)		(a)	53		267		(55)		252
Total revenues(b)	$	1,015		$	539	$	267	$	(55)	$	1,766
Six Months 2023:
Residential	$	719		$	394	$	—	$	—	$	1,113
Commercial	393			102		—		—		495
Industrial	96			9		—		—		105
Other	(44)		(a)	38		227		(54)		167
Total revenues(b)	$	1,164		$	543	$	227	$	(54)	$	1,880

(a)Includes over-recoveries of various riders.

(b)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 and six months ended June 30, 2024 and 2023:


	Ameren Illinois Electric Distribution		Ameren Illinois Natural Gas		Ameren Illinois Transmission		Ameren Illinois
Three Months 2024:
Revenues from alternative revenue programs	$	22	$	—	$	2	$	24
Other revenues not from contracts with customers	1		1		—		2
Three Months 2023:
Revenues from alternative revenue programs	$	60	$	9	$	3	$	72
Other revenues not from contracts with customers	2		1		—		3
Six Months 2024:
Revenues from alternative revenue programs	$	61	$	19	$	10	$	90
Other revenues not from contracts with customers	3		2		—		5
Six Months 2023:
Revenues from alternative revenue programs	$	124	$	37	$	10	$	171
Other revenues not from contracts with customers	4		2		—		6

Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Basis Of Presentation And Significant Accounting Policies [Line Items]
Unconsolidated variable interest	$ 75	$ 73
Cash Surrender Value of Life Insurance	255	248
Corporate owned life insurance, borrowings	103	104
Ameren Illinois Company
Basis Of Presentation And Significant Accounting Policies [Line Items]
Cash Surrender Value of Life Insurance	114	111
Corporate owned life insurance, borrowings	103	$ 104
Partnership Funding Commitment
Basis Of Presentation And Significant Accounting Policies [Line Items]
Outstanding funding commitments	$ 12

Rate And Regulatory Matters (Narrative-Missouri) (Details) $ in Millions	1 Months Ended	3 Months Ended					6 Months Ended		12 Months Ended
	Nov. 30, 2023 USD ($)	Jun. 30, 2024 MWh	Sep. 30, 2023 MWh	Dec. 31, 2022 MWh	Sep. 30, 2022 MWh	Jun. 30, 2022 MWh	Jun. 30, 2024 USD ($) MWh	Jun. 30, 2023 USD ($)	Dec. 31, 2025 USD ($)
Rate And Regulatory Matters [Line Items]
Capital expenditures							$ 1,892	$ 1,822
Union Electric Company
Rate And Regulatory Matters [Line Items]
Capital expenditures							1,104	$ 914
Cass County Solar Project Purchase Price							250
Union Electric Company \| Rush Island Energy Center
Rate And Regulatory Matters [Line Items]
MoPSC Approved Costs to be Securitized							$ 470
Requested Costs to be Securitized	$ 519
Regulatory Asset, Amortization Period	15 years
Union Electric Company \| Solar generation facility
Rate And Regulatory Matters [Line Items]
Amount of Megawatts \| MWh							500
Capital expenditures							$ 850
Union Electric Company \| Electric \| Pending Rate Case
Rate And Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount							$ 446
Public Utilities, Requested Return on Equity, Percentage							10.25%
Public Utilities, Requested Equity Capital Structure, Percentage							52.00%
Rate Base							$ 14,000
Months to complete a rate proceeding							11 months
Union Electric Company \| Electric \| MEEIA 2024 \| Forecast
Rate And Regulatory Matters [Line Items]
Energy efficiency investments in MEEIA 2019 programs									$ 123
Percentage of MEEIA Energy Efficiency Goals Achieved									100.00%
Incentive award if energy efficiency goals are achieved									$ 56
Incentive award if energy efficiency goals are exceeded									$ 14
Union Electric Company \| Build-transfer \| Solar generation facility
Rate And Regulatory Matters [Line Items]
Amount of Megawatts \| MWh			300		200	150
Union Electric Company \| Development-transfer \| Solar generation facility
Rate And Regulatory Matters [Line Items]
Amount of Megawatts \| MWh			150
Union Electric Company \| Self-build \| Solar generation facility
Rate And Regulatory Matters [Line Items]
Amount of Megawatts \| MWh			50	50
Union Electric Company \| Self-build \| Natural Gas Generation Facility
Rate And Regulatory Matters [Line Items]
Amount of Megawatts \| MWh		800

Rate And Regulatory Matters (Narrative-Illinois) (Details) - USD ($) $ in Millions	1 Months Ended			3 Months Ended	6 Months Ended		12 Months Ended
	Dec. 31, 2023	Nov. 30, 2023	Oct. 31, 2023	Sep. 30, 2024	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2027	Dec. 31, 2026	Dec. 31, 2025	Dec. 31, 2024
Rate And Regulatory Matters [Line Items]
Capital expenditures					$ 1,892	$ 1,822
Ameren Illinois Company
Rate And Regulatory Matters [Line Items]
Capital expenditures					717	$ 844
Ameren Illinois Company \| Natural gas
Rate And Regulatory Matters [Line Items]
Public Utilities, Requested Equity Capital Structure, Percentage	52.00%
Public Utilities, Requested Return on Equity, Percentage	9.89%
IETL \| Ameren Illinois Company \| Electric Distribution \| Forecast
Rate And Regulatory Matters [Line Items]
Approved return on equity percentage							8.72%	8.72%	8.72%	8.72%
Multi-year rate plan rehearing approved revenue requirement							$ 1,397	$ 1,350	$ 1,282	$ 1,196
Approved rate base							4,700	4,500	4,300	4,000
Revised multi-year rate plan requested revenue requirement							1,446	1,386	1,300	1,215
Revised multi-year rate plan requested rate base							5,000	4,800	4,500	4,300
ICC staff revised multi-year rate plan recommended revenue requirement							1,414	1,361	1,281	1,201
ICC staff revised multi-year rate plan recommended rate base							$ 4,800	$ 4,600	$ 4,400	$ 4,200
Public Utilities, Approved Equity Capital Structure, Percentage							50.00%	50.00%	50.00%	50.00%
Public Utilities, Approved Rate Increase (Decrease), Amount										$ 285
Public Utilities, Requested Rate Increase (Decrease), Amount										334
ICC staff recommended rate increase										$ 302
Pending Rate Case \| Ameren Illinois Company \| Electric Distribution
Rate And Regulatory Matters [Line Items]
ICC staff recommended rate increase					157
Pending Rate Case \| Ameren Illinois Company \| Electric Distribution \| Subsequent Event
Rate And Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount				$ 158
Public Utilities, Requested Equity Capital Structure, Percentage				50.00%
Pending Rate Case \| Ameren Illinois Company \| Electric Energy-Efficiency
Rate And Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount					$ 26
Pending Rate Case \| Ameren Illinois Company \| Natural gas
Rate And Regulatory Matters [Line Items]
Capital expenditures			$ 53
Over-Recovery Challenged by the Attorney General			$ 3
Final Rate Order \| Ameren Illinois Company \| Natural gas
Rate And Regulatory Matters [Line Items]
Approved return on equity percentage		9.44%
Approved rate base		$ 2,850
Public Utilities, Approved Equity Capital Structure, Percentage		50.00%
Public Utilities, Requested Rate Increase (Decrease), Amount		$ 112
Capital expenditures	$ 93	$ 93

Rate And Regulatory Matters (Narrative-Federal) (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	May 31, 2020	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Rate And Regulatory Matters [Line Items]
ROE Change				0.50%
Revenues		$ 1,693	$ 1,760	$ 3,509	$ 3,822
Ameren Illinois Company
Rate And Regulatory Matters [Line Items]
Revenues		$ 766	$ 779	1,766	$ 1,880
Midwest Independent Transmission System Operator, Inc
Rate And Regulatory Matters [Line Items]
Revenues				21
Midwest Independent Transmission System Operator, Inc \| Ameren Illinois Company
Rate And Regulatory Matters [Line Items]
Revenues				$ 15
Midwest Independent Transmission System Operator, Inc \| Final Rate Order
Rate And Regulatory Matters [Line Items]
Approved return on equity percentage	10.02%

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481687/323-10-50-3

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 28
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482907/825-10-50-28

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(1))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483621/220-10-S99-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(i))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1A

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(ii))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1A

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iii)(A))
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-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1A

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iv))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1A

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(5))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1A

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(i))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1B

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(A))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1B

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(B))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1B

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iv))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1B

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(5))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1B

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 30
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-30

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-42

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-22

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 40
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-40

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-22

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 41
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-41

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 235
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-05(b)(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479557/942-235-S99-1

+ Details

Short-Term Debt And Liquidity (Narrative) (Details) $ in Billions	3 Months Ended		6 Months Ended
	Jun. 30, 2024 USD ($)	Jun. 30, 2023	Jun. 30, 2024 USD ($)	Jun. 30, 2023
Credit Agreements
Short-term Debt [Line Items]
Net Liquidity Available	$ 1.9		$ 1.9
Actual debt-to-capital ratio	0.61		0.61
Utilities
Short-term Debt [Line Items]
Short-term Debt, Weighted Average Interest Rate, over Time	5.51%	5.28%	5.41%	5.04%
Union Electric Company \| Missouri Credit Agreement
Short-term Debt [Line Items]
Actual debt-to-capital ratio	0.49		0.49
Ameren Illinois Company \| Illinois Credit Agreement
Short-term Debt [Line Items]
Actual debt-to-capital ratio	0.45		0.45

Short-Term Debt and Liquidity (Short-Term Debt outstanding) (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Short-term Debt [Line Items]
Short-term debt	$ 691	$ 536
Union Electric Company
Short-term Debt [Line Items]
Short-term debt	390	170
Ameren Illinois Company
Short-term Debt [Line Items]
Short-term debt	0	366
Commercial Paper
Short-term Debt [Line Items]
Short-term debt	691	536
Commercial Paper \| Parent Company
Short-term Debt [Line Items]
Short-term debt	301	0
Commercial Paper \| Union Electric Company
Short-term Debt [Line Items]
Short-term debt	390	170
Commercial Paper \| Ameren Illinois Company
Short-term Debt [Line Items]
Short-term debt	$ 0	$ 366

Short-Term Debt and Liquidity (Short-Term Debt Activity) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Short-term Debt [Line Items]
Average daily amount outstanding	$ 578	$ 1,168
Weighted-average interest rate	5.56%	5.10%
Short-term Debt, Maximum Amount Outstanding During Period	$ 1,084	$ 1,381
Peak interest rate	5.68%	5.60%
Parent Company
Short-term Debt [Line Items]
Average daily amount outstanding	$ 84	$ 595
Weighted-average interest rate	5.55%	5.14%
Short-term Debt, Maximum Amount Outstanding During Period	$ 301	$ 841
Peak interest rate	5.60%	5.55%
Union Electric Company
Short-term Debt [Line Items]
Average daily amount outstanding	$ 109	$ 343
Weighted-average interest rate	5.53%	5.04%
Short-term Debt, Maximum Amount Outstanding During Period	$ 509	$ 592
Peak interest rate	5.68%	5.55%
Ameren Illinois Company
Short-term Debt [Line Items]
Average daily amount outstanding	$ 385	$ 230
Weighted-average interest rate	5.57%	5.10%
Short-term Debt, Maximum Amount Outstanding During Period	$ 694	$ 450
Peak interest rate	5.68%	5.60%

Long-Term debt and Equity Financings (Details) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2024 USD ($) shares	Mar. 31, 2024 USD ($) shares	Jun. 30, 2023 USD ($) shares	Jun. 30, 2024 USD ($) $ / shares shares	Jun. 30, 2023 USD ($) shares	Apr. 30, 2024 USD ($)	Jan. 31, 2024 USD ($)
Long-Term Debt And Equity Financings [Line Items]
Shares issued under the DRPlus and 401(k) plan \| shares	0.2		0.1	0.3	0.2
Issuances of common stock				$ 21.0	$ 16.0
Stock Issued During Period, Shares, Other \| shares	0.0	0.2	0.0	0.2	0.5
Stock Issued During Period, Value, Other		$ 16.0
Maximum Value Of Shares To Be Issued Under ATM Program	$ 770.0			$ 770.0
Forward Contract Indexed to Issuer's Equity, Basis Spread	75			75
Minimum
Long-Term Debt And Equity Financings [Line Items]
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share \| $ / shares				$ 76.69
Maximum
Long-Term Debt And Equity Financings [Line Items]
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share \| $ / shares				89.31
Weighted Average
Long-Term Debt And Equity Financings [Line Items]
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share \| $ / shares				$ 80.45
Dividend reinvestment and 401 (k) plans
Long-Term Debt And Equity Financings [Line Items]
Issuances of common stock	$ 4.0			$ 14.0
Accrued Proceeds from Issuance of Common Stock				$ 7.0
Forward Sale Agreements Outstanding
Long-Term Debt And Equity Financings [Line Items]
Forward Contract Indexed to Issuer's Equity, Settlement Alternatives, Shares, at Fair Value \| shares	2.9			2.9
Forward Contract Indexed to Issuer's Equity, Settlement Alternatives, Cash, at Fair Value	$ 232.0			$ 232.0
Period End Net Cash Settlement Price	29.0			29.0
Period End Net Share Settlement Price	$ 0.4			$ 0.4
Forward Sale Agreement Equity Offering Shares \| shares	2.9			2.9
Forward Sale Agreement Gross Sales Price	$ 232.0			$ 232.0
Union Electric Company
Long-Term Debt And Equity Financings [Line Items]
Capital contributions from parent				350.0	$ 0.0
Union Electric Company \| Other Paid-in Capital:
Long-Term Debt And Equity Financings [Line Items]
Capital contributions from parent	350.0		$ 0.0	350.0	$ 0.0
Union Electric Company \| Secured Debt \| First Mortgage Bonds, 5.25%, Due 2054 - $350 Issuance
Long-Term Debt And Equity Financings [Line Items]
Debt Instrument, Face Amount							$ 350.0
Debt Instrument, Interest Rate, Stated Percentage							5.25%
Union Electric Company \| Secured Debt \| Senior Secured Notes 5.20% Due 2034
Long-Term Debt And Equity Financings [Line Items]
Debt Instrument, Face Amount						$ 500.0
Debt Instrument, Interest Rate, Stated Percentage						5.20%
Union Electric Company \| Secured Debt \| Senior Secured Notes350 Due2024
Long-Term Debt And Equity Financings [Line Items]
Debt Instrument, Face Amount						$ 350.0
Debt Instrument, Interest Rate, Stated Percentage						3.50%
Ameren Illinois Company \| Secured Debt \| First Mortgage Bonds, 5.55%, Due 2054 - $625 Issuance
Long-Term Debt And Equity Financings [Line Items]
Debt Instrument, Face Amount	$ 625.0			$ 625.0
Debt Instrument, Interest Rate, Stated Percentage	5.55%			5.55%

Other Income, Net (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
Other Income, Net (Details) - USD ($) $ in Millions	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Other Nonoperating Income (Expense) [Line Items]
Allowance for equity funds used during construction	$ 16	$ 14	$ 25	$ 23
Other interest income	13	9	21	17
Non-service cost components of net periodic benefit income	76	63	152	127
Miscellaneous income	4	2	6	4
Income (Loss) from Equity Method Investments	1	0	1	2
Donations	(2)	(2)	(4)	(4)
Miscellaneous expense	(5)	(4)	(9)	(9)
Total Other Income, Net	103	82	192	160
Union Electric Company
Other Nonoperating Income (Expense) [Line Items]
Allowance for equity funds used during construction	14	8	23	12
Other interest income	3	2	5	6
Non-service cost components of net periodic benefit income	35	14	69	28
Miscellaneous income	0	1	2	2
Donations	(1)	(1)	(2)	(2)
Miscellaneous expense	(2)	(2)	(4)	(5)
Total Other Income, Net	49	22	93	41
Defined Benefit Plan, Non-service Cost or Income Components - Tracker	(11)	17	(20)	34
Ameren Illinois Company
Other Nonoperating Income (Expense) [Line Items]
Allowance for equity funds used during construction	2	6	2	10
Other interest income	9	6	15	10
Non-service cost components of net periodic benefit income	26	31	53	62
Miscellaneous income	2	1	3	2
Donations	(1)	(1)	(2)	(2)
Miscellaneous expense	(1)	(2)	(3)	(4)
Total Other Income, Net	$ 37	$ 41	$ 68	$ 78

Derivative Financial Instruments (Open Gross Derivative Volumes By Commodity Type) (Detail) lb in Thousands, gal in Millions, MWh in Millions, MMBTU in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2024 MWh MMBTU lb gal	Dec. 31, 2023 MWh MMBTU lb gal
Fuel oils
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume \| gal	20	17
Natural gas
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure \| MMBTU	273	271
Power
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure \| MWh	5	5
Uranium
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass \| lb	0	186
Union Electric Company \| Fuel oils
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume \| gal	20	17
Union Electric Company \| Natural gas
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure \| MMBTU	52	53
Union Electric Company \| Power
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure \| MWh	0	0
Union Electric Company \| Uranium
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass \| lb	0	186
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	221	218
Ameren Illinois Company \| Power
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure \| MWh	5	5
Ameren Illinois Company \| Uranium
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass \| lb	0	0

Derivative Financial Instruments (Derivative Instruments Carrying Value) (Detail) - Not Designated As Hedging Instrument - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Derivative [Line Items]
Derivative Assets	$ 24	$ 22
Derivative Liability	141	168
Fuel oils \| Other current assets
Derivative [Line Items]
Derivative Assets	2	2
Fuel oils \| Other current liabilities
Derivative [Line Items]
Derivative Liability	1	1
Fuel oils \| Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	0	1
Natural gas \| Other current assets
Derivative [Line Items]
Derivative Assets	4	0
Natural gas \| Other assets
Derivative [Line Items]
Derivative Assets	3	6
Natural gas \| Other current liabilities
Derivative [Line Items]
Derivative Liability	42	57
Natural gas \| Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	36	40
Power \| Other current assets
Derivative [Line Items]
Derivative Assets	15	5
Power \| Other current liabilities
Derivative [Line Items]
Derivative Liability	12	13
Power \| Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	50	56
Uranium \| Other current assets
Derivative [Line Items]
Derivative Assets	0	9
Union Electric Company
Derivative [Line Items]
Derivative Assets	20	19
Derivative Liability	19	25
Union Electric Company \| Fuel oils \| Other current assets
Derivative [Line Items]
Derivative Assets	2	2
Union Electric Company \| Fuel oils \| Other current liabilities
Derivative [Line Items]
Derivative Liability	1	1
Union Electric Company \| Fuel oils \| Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	0	1
Union Electric Company \| Natural gas \| Other current assets
Derivative [Line Items]
Derivative Assets	1	0
Union Electric Company \| Natural gas \| Other assets
Derivative [Line Items]
Derivative Assets	2	3
Union Electric Company \| Natural gas \| Other current liabilities
Derivative [Line Items]
Derivative Liability	9	12
Union Electric Company \| Natural gas \| Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	8	10
Union Electric Company \| Power \| Other current assets
Derivative [Line Items]
Derivative Assets	15	5
Union Electric Company \| Power \| Other current liabilities
Derivative [Line Items]
Derivative Liability	1	1
Union Electric Company \| Power \| Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	0	0
Union Electric Company \| Uranium \| Other current assets
Derivative [Line Items]
Derivative Assets	0	9
Ameren Illinois Company
Derivative [Line Items]
Derivative Assets	4	3
Derivative Liability	122	143
Ameren Illinois Company \| Fuel oils \| Other current assets
Derivative [Line Items]
Derivative Assets	0	0
Ameren Illinois Company \| Fuel oils \| Other current liabilities
Derivative [Line Items]
Derivative Liability	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	3	0
Ameren Illinois Company \| Natural gas \| Other assets
Derivative [Line Items]
Derivative Assets	1	3
Ameren Illinois Company \| Natural gas \| Other current liabilities
Derivative [Line Items]
Derivative Liability	33	45
Ameren Illinois Company \| Natural gas \| Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	28	30
Ameren Illinois Company \| Power \| Other current assets
Derivative [Line Items]
Derivative Assets	0	0
Ameren Illinois Company \| Power \| Other current liabilities
Derivative [Line Items]
Derivative Liability	11	12
Ameren Illinois Company \| Power \| Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	50	56
Ameren Illinois Company \| Uranium \| Other current assets
Derivative [Line Items]
Derivative Assets	$ 0	$ 0

Derivative Financial Instruments (Offsetting Assets and Liabilities) (Details) - Not Designated As Hedging Instrument - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Derivative [Line Items]
Gross derivative asset amount recognized on the balance sheet	$ 24	$ 22
Gross derivative instruments not offset in the balance sheet	7	7
Gross cash collateral received not offset in the balance sheet	0	0
Net derivative asset	17	15
Gross derivative liability amount recognized on the balance sheet	141	168
Gross derivative instruments not offset in the balance sheet	7	7
Gross cash collateral posted not offset in the balance sheet	0	6
Net derivative liability	134	155
Union Electric Company
Derivative [Line Items]
Gross derivative asset amount recognized on the balance sheet	20	19
Gross derivative instruments not offset in the balance sheet	5	6
Gross cash collateral received not offset in the balance sheet	0	0
Net derivative asset	15	13
Gross derivative liability amount recognized on the balance sheet	19	25
Gross derivative instruments not offset in the balance sheet	5	6
Gross cash collateral posted not offset in the balance sheet	0	0
Net derivative liability	14	19
Ameren Illinois Company
Derivative [Line Items]
Gross derivative asset amount recognized on the balance sheet	4	3
Gross derivative instruments not offset in the balance sheet	2	1
Gross cash collateral received not offset in the balance sheet	0	0
Net derivative asset	2	2
Gross derivative liability amount recognized on the balance sheet	122	143
Gross derivative instruments not offset in the balance sheet	2	1
Gross cash collateral posted not offset in the balance sheet	0	6
Net derivative liability	$ 120	$ 136

Derivative Financial Instruments (Derivative Instruments with Credit Risk-Related Contingent Features) (Details) $ in Millions	Jun. 30, 2024 USD ($)
Derivative [Line Items]
Aggregate Fair Value of Derivative Liabilities	$ 80
Cash Collateral Posted	0
Potential Aggregate Amount of Additional Collateral Required	72
Union Electric Company
Derivative [Line Items]
Aggregate Fair Value of Derivative Liabilities	19
Cash Collateral Posted	0
Potential Aggregate Amount of Additional Collateral Required	13
Ameren Illinois Company
Derivative [Line Items]
Aggregate Fair Value of Derivative Liabilities	61
Cash Collateral Posted	0
Potential Aggregate Amount of Additional Collateral Required	$ 59

Fair Value Measurements (Schedule Of Fair Value Hierarchy Of Assets And Liabilities Measured At Fair Value On Recurring Basis) (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	$ 1,256	$ 1,141
Assets fair value	1,280	1,163
Excluded receivables, payables, and accrued income, net	10	9
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	842	787
Assets fair value	843	789
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	414	354
Assets fair value	418	358
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Assets fair value	19	16
Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Assets	24	22
Derivative Liability	141	168
Commodity Contract \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Assets	1	2
Derivative Liability	3	6
Commodity Contract \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Assets	4	4
Derivative Liability	68	79
Commodity Contract \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Assets	19	16
Derivative Liability	70	83
Union Electric Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	1,256	1,141
Assets fair value	1,276	1,160
Union Electric Company \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	842	787
Assets fair value	843	789
Union Electric Company \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	414	354
Assets fair value	417	357
Union Electric Company \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Assets fair value	16	14
Union Electric Company \| Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Assets	20	19
Derivative Liability	19	25
Union Electric Company \| Commodity Contract \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Assets	1	2
Derivative Liability	1	2
Union Electric Company \| Commodity Contract \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Assets	3	3
Derivative Liability	16	19
Union Electric Company \| Commodity Contract \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Assets	16	14
Derivative Liability	2	4
Union Electric Company \| Fuel oils \| Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Assets	2	2
Derivative Liability	1	2
Union Electric Company \| Fuel oils \| Commodity Contract \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Assets	1	2
Derivative Liability	1	2
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	1	0
Derivative Liability	0	0
Union Electric Company \| Natural gas \| Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Assets	3	3
Derivative Liability	17	22
Union Electric Company \| Natural gas \| Commodity Contract \| Level 1
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 \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Assets	3	3
Derivative Liability	16	19
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	1	3
Union Electric Company \| Power \| Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Assets	15	5
Derivative Liability	1	1
Union Electric Company \| Power \| Commodity Contract \| Level 1
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 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	15	5
Derivative Liability	1	1
Union Electric Company \| Uranium \| Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Assets	0	9
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	0	9
Union Electric Company \| Equity securities: \| U.S. large capitalization
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	842	787
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:	842	787
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:	178	150
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:	178	150
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:	154	136
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:	154	136
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:	82	68
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:	82	68
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	4	3
Ameren Illinois Company \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets fair value	0	0
Ameren Illinois Company \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets fair value	1	1
Ameren Illinois Company \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets fair value	3	2
Ameren Illinois Company \| Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liability	122	143
Ameren Illinois Company \| Commodity Contract \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liability	2	4
Ameren Illinois Company \| Commodity Contract \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liability	52	60
Ameren Illinois Company \| Commodity Contract \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liability	68	79
Ameren Illinois Company \| Natural gas \| Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Assets	4	3
Derivative Liability	61	75
Ameren Illinois Company \| Natural gas \| Commodity Contract \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Assets	0	0
Derivative Liability	2	4
Ameren Illinois Company \| Natural gas \| Commodity Contract \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Assets	1	1
Derivative Liability	52	60
Ameren Illinois Company \| Natural gas \| Commodity Contract \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Assets	3	2
Derivative Liability	7	11
Ameren Illinois Company \| Power \| Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liability	61	68
Ameren Illinois Company \| Power \| Commodity Contract \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liability	0	0
Ameren Illinois Company \| Power \| Commodity Contract \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liability	0	0
Ameren Illinois Company \| Power \| Commodity Contract \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liability	$ 61	$ 68

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		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ (52)	$ (47)	$ (64)	$ (21)
Included in regulatory assets/liabilities	3	(6)	12	(33)
Settlements, assets	2			0
Settlement, liabilities		(1)	5
Change in unrealized gains (losses) related to assets/liabilities held at period end	2	(6)	14	(21)
Ending balance	(47)	(54)	(47)	(54)
Union Electric Company
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	2	5	4	12
Included in regulatory assets/liabilities	15	14	14	8
Settlements, assets				6
Settlement, liabilities	(3)	(5)	(4)
Change in unrealized gains (losses) related to assets/liabilities held at period end	14	14	14	14
Ending balance	14	14	14	14
Ameren Illinois Company
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	(54)	(52)	(68)	(33)
Included in regulatory assets/liabilities	(12)	(20)	(2)	(41)
Settlements, assets	5	4	9
Settlement, liabilities				6
Change in unrealized gains (losses) related to assets/liabilities held at period end	(12)	(20)	0	(35)
Ending balance	$ (61)	$ (68)	$ (61)	$ (68)

Fair Value Measurements (Schedule Of Valuation Process And Unobservable Inputs) (Details) - Power $ in Millions	Jun. 30, 2024 USD ($) $ / MWh	Dec. 31, 2023 USD ($) $ / MWh
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative Assets \| $	$ 15	$ 5
Derivative liabilities \| $	$ (62)	$ (69)
Commodity Forward Price \| Discounted cash flow \| Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Measurement input	33	31
Commodity Forward Price \| Discounted cash flow \| Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Measurement input	70	65
Commodity Forward Price \| Discounted cash flow \| Weighted Average
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Measurement input	43	43
Nodal Basis \| Discounted cash flow \| Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Measurement input	(10)	(8)
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	(5)	(5)

Fair Value Measurements (Schedule Of Carrying Amounts And Estimated Fair Values Of Financial Assets and Liabilities) (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Carrying Amount(a)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-Term Debt, Carrying Amount	$ 17,079	$ 15,970
Debt Issuance Costs, Net	124	111
Carrying Amount(a) \| Union Electric Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-Term Debt, Carrying Amount	6,830	6,341
Debt Issuance Costs, Net	53	45
Carrying Amount(a) \| Ameren Illinois Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-Term Debt, Carrying Amount	5,851	5,232
Debt Issuance Costs, Net	52	47
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	15,450	14,833
Fair Value \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	14,990	14,366
Fair Value \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	460	467
Fair Value \| Union Electric Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	6,069	5,800
Fair Value \| Union Electric Company \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	6,069	5,800
Fair Value \| Union Electric Company \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	0	0
Fair Value \| Ameren Illinois Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	5,251	4,867
Fair Value \| Ameren Illinois Company \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	5,251	4,867
Fair Value \| Ameren Illinois Company \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	$ 0	$ 0

Related Party Transactions (Narrative) (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Related Party Transaction [Line Items]
Other assets	$ 1,049	$ 921
Union Electric Company
Related Party Transaction [Line Items]
Other assets	194	152
Ameren Illinois Company
Related Party Transaction [Line Items]
Other assets	656	603
Ameren Services Support Services Agreement \| Union Electric Company \| Related Party
Related Party Transaction [Line Items]
Other assets	22	31
Ameren Services Support Services Agreement \| Ameren Illinois Company \| Related Party
Related Party Transaction [Line Items]
Other assets	$ 24	$ 34

Related Party Transactions (Schedule of Affiliate Receivables and Payables) (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	$ 774	$ 1,136
Accounts Receivable, Related Parties, Current	514	494
Union Electric Company \| Related Party
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	58	53
Accounts Receivable, Related Parties, Current	67	72
Union Electric Company \| Income taxes payable to parent \| Related Party
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	0	0
Union Electric Company \| Income taxes receivable from parent \| Related Party
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties, Current	54	56
Ameren Illinois Company \| Related Party
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	97	52
Accounts Receivable, Related Parties, Current	11	35
Ameren Illinois Company \| Income taxes payable to parent \| Related Party
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	44	2
Ameren Illinois Company \| Income taxes receivable from parent \| Related Party
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties, Current	$ 0	$ 22

Related Party Transactions (Effects of Related-party Transactions on the Statement of Income) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Related Party Transaction [Line Items]
Operating Revenues	$ 1,693	$ 1,760	$ 3,509	$ 3,822
Other operations and maintenance	465	450	935	898
(Interest Charges)/Other Income, Net	(165)	(134)	(319)	(261)
Union Electric Company
Related Party Transaction [Line Items]
Operating Revenues	888	941	1,663	1,864
Other operations and maintenance	247	237	501	476
(Interest Charges)/Other Income, Net	(63)	(52)	(125)	(103)
Union Electric Company \| Ameren Missouri Power Supply Agreements with Ameren Illinois \| Related Party
Related Party Transaction [Line Items]
Operating Revenues	1	1	1	1
Union Electric Company \| Ameren Missouri and Ameren Illinois Rent and Facility Services \| Related Party
Related Party Transaction [Line Items]
Operating Revenues	8	8	15	18
Other operations and maintenance	1	1	1	1
Union Electric Company \| Ameren Missouri and Ameren Illinois Miscellaneous Support Services \| Related Party
Related Party Transaction [Line Items]
Operating Revenues	1	1	1	1
Union Electric Company \| Total Related Party Operating Revenues \| Related Party
Related Party Transaction [Line Items]
Operating Revenues	9	8	16	18
Union Electric Company \| Ameren Missouri and Ameren Illinois Transmission Services from ATXI \| Related Party
Related Party Transaction [Line Items]
Purchased Power	2	1	4	1
Union Electric Company \| Purchased Power \| Related Party
Related Party Transaction [Line Items]
Purchased Power	2	1	4	1
Union Electric Company \| Ameren Services Support Services Agreement \| Related Party
Related Party Transaction [Line Items]
Other operations and maintenance	43	35	81	70
Union Electric Company \| Total Related Party Other Operations and Maintenance \| Related Party
Related Party Transaction [Line Items]
Other operations and maintenance	43	35	81	70
Union Electric Company \| Money pool interest \| Related Party
Related Party Transaction [Line Items]
(Interest Charges)/Other Income, Net	(1)	(1)	(3)	(1)
Ameren Illinois Company
Related Party Transaction [Line Items]
Operating Revenues	766	779	1,766	1,880
Purchased Power	141	192	305	479
Other operations and maintenance	224	201	434	403
(Interest Charges)/Other Income, Net	(60)	(50)	(115)	(97)
Ameren Illinois Company \| Ameren Missouri and Ameren Illinois Rent and Facility Services \| Related Party
Related Party Transaction [Line Items]
Operating Revenues	1	1	1	1
Other operations and maintenance	1	1	1	2
Ameren Illinois Company \| Ameren Missouri and Ameren Illinois Miscellaneous Support Services \| Related Party
Related Party Transaction [Line Items]
Operating Revenues	1	1	1	1
Ameren Illinois Company \| Total Related Party Operating Revenues \| Related Party
Related Party Transaction [Line Items]
Operating Revenues	1	1	1	1
Ameren Illinois Company \| Ameren Illinois Power Supply Agreements with Ameren Missouri \| Related Party
Related Party Transaction [Line Items]
Purchased Power	1	1	1	1
Ameren Illinois Company \| Ameren Missouri and Ameren Illinois Transmission Services from ATXI \| Related Party
Related Party Transaction [Line Items]
Purchased Power	1	1	1	1
Ameren Illinois Company \| Purchased Power \| Related Party
Related Party Transaction [Line Items]
Purchased Power	1	1	1	1
Ameren Illinois Company \| Ameren Services Support Services Agreement \| Related Party
Related Party Transaction [Line Items]
Other operations and maintenance	40	33	77	68
Ameren Illinois Company \| Total Related Party Other Operations and Maintenance \| Related Party
Related Party Transaction [Line Items]
Other operations and maintenance	40	33	77	70
Ameren Illinois Company \| Money pool interest \| Related Party
Related Party Transaction [Line Items]
(Interest Charges)/Other Income, Net	$ (1)	$ (1)	$ (2)	$ (1)

Commitments And Contingencies (Environmental Matters) (Detail) $ in Millions	Jun. 30, 2024 USD ($) scrubber site	May 30, 2024 USD ($)	Dec. 31, 2023 USD ($)
Loss Contingencies [Line Items]
Asset Retirement Obligation	$ 810		$ 791
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	$ 807		787
Union Electric Company \| Coal Fired Electric Generation Equipment
Loss Contingencies [Line Items]
Plant To Be Abandoned, Net	508
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	3		$ 4
Rush Island Energy Center Additional Mitigation Relief Proposed by Ameren Missouri \| Union Electric Company
Loss Contingencies [Line Items]
Estimate of possible loss	20
Accrual for environmental loss contingencies	20
Rush Island Energy Center Additional Mitigation Relief Proposed by Department of Justice \| Union Electric Company
Loss Contingencies [Line Items]
Estimate of possible loss		$ 120
Manufactured Gas Plant
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies	45
Manufactured Gas Plant \| Ameren Illinois Company
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies	$ 45
Number of remediation sites \| site	44
Manufactured Gas Plant \| Ameren Illinois Company \| Minimum
Loss Contingencies [Line Items]
Estimate of possible loss	$ 45
Manufactured Gas Plant \| Ameren Illinois Company \| Maximum
Loss Contingencies [Line Items]
Estimate of possible loss	95
New CCR Rules Estimate
Loss Contingencies [Line Items]
Asset Retirement Obligation	42
New CCR Rules Estimate \| Union Electric Company
Loss Contingencies [Line Items]
Asset Retirement Obligation	$ 42

Callaway Energy Center (Insurance Disclosure) (Details) $ in Millions	6 Months Ended
	Jun. 30, 2024 USD ($) yr
Nuclear Waste Matters [Line Items]
Decommissioning Cost	$ 7.0
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	$ 500.0
Insurance Maximum Coverage per Incident	0.0
Public Liability And Nuclear Worker Liability - Pool Participation
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	15,763.0
Insurance Maximum Coverage per Incident	166.0
Threshold Amount For Retrospective Insurance Assessment For Covered Loss Under Public Liability And Nuclear Worker Liability Insurance Policy	500.0
Maximum Annual Payment Per Incident At Licensed Commercial Nuclear Reactor	24.7
Public Liability
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	16,263.0
Insurance Maximum Coverage per Incident	166.0
Property Damage - Nuclear Electric Insurance Ltd
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	3,200.0
Insurance Maximum Coverage per Incident	28.0
Accidental Outage - Nuclear Electric Insurance Ltd
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	490.0
Insurance Maximum Coverage per Incident	11.0
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	490.0
Sub-Limit Of Amount Of Weekly Indemnity Coverage Thereafter Not Exceeding Policy Limit For Non-Nuclear Events	291.0
Radiation Event
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	2,700.0
Aggregate Nuclear Power Industry Insurance Policy Limit For Losses From Terrorist Attacks Within Twelve Month Period	3,200.0
Non-Radiation Event
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	700.0
Aggregate Nuclear Power Industry Insurance Policy Limit For Losses From Terrorist Attacks Within Twelve Month Period	1,800.0
Property Damage European Mutual Association for Nuclear Insurance
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	$ 490.0

Retirement Benefits (Components Of Net Periodic Benefit Cost) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total non-service cost components	$ (76)	$ (63)	$ (152)	$ (127)
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	23	23	44	46
Interest cost	56	56	111	111
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	(82)	(84)	(164)	(167)
Prior service benefit	0	0	0	0
Actuarial (gain)	(16)	(28)	(33)	(57)
Total non-service cost components	(42)	(56)	(86)	(113)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Total	(19)	(33)	$ (42)	(67)
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	3	$ 6	6
Interest cost	11	12	22	23
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	(23)	(23)	(46)	(46)
Prior service benefit	(1)	(1)	(2)	(2)
Actuarial (gain)	(10)	(12)	(20)	(23)
Total non-service cost components	(23)	(24)	(46)	(48)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Total	$ (20)	$ (21)	$ (40)	$ (42)
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 Benefit Plan Costs Incurred) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	$ (19)	$ (33)	$ (42)	$ (67)
Pension Plan \| Union Electric Company
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	(10)	(17)	(22)	(35)
Pension Plan \| Ameren Illinois Company
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	(8)	(13)	(17)	(27)
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	(1)	(3)	(3)	(5)
Other Postretirement Benefit Plan, Defined Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	(20)	(21)	(40)	(42)
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	(7)	(7)	(14)	(15)
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)	(14)	(26)	(27)
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	$ 0	$ 0

Income Taxes (Schedule of Effective Income Tax Rate Reconciliation) (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Income Taxes [Line Items]
Federal statutory corporate income tax rate	21.00%	21.00%	21.00%	21.00%
Increases (decreases) from:
Amortization of excess deferred taxes	(8.00%)	(7.00%)	(8.00%)	(8.00%)
Renewable and other tax credits	(4.00%)	(5.00%)	(4.00%)	(4.00%)
State tax	5.00%	5.00%	5.00%	5.00%
Depreciation differences	(1.00%)	0.00%	0.00%	0.00%
Other permanent items			0.00%	(1.00%)
Effective income tax rate	13.00%	14.00%	14.00%	13.00%
Union Electric Company
Income Taxes [Line Items]
Federal statutory corporate income tax rate	21.00%	21.00%	21.00%	21.00%
Increases (decreases) from:
Amortization of excess deferred taxes	(14.00%)	(15.00%)	(14.00%)	(15.00%)
Renewable and other tax credits	(8.00%)	(10.00%)	(8.00%)	(10.00%)
State tax	3.00%	3.00%	3.00%	3.00%
Depreciation differences	(1.00%)	0.00%	0.00%	0.00%
Other permanent items			0.00%	0.00%
Effective income tax rate	1.00%	(1.00%)	2.00%	(1.00%)
Ameren Illinois Company
Income Taxes [Line Items]
Federal statutory corporate income tax rate	21.00%	21.00%	21.00%	21.00%
Increases (decreases) from:
Amortization of excess deferred taxes	(4.00%)	(2.00%)	(4.00%)	(2.00%)
Renewable and other tax credits	0.00%	0.00%	0.00%	0.00%
State tax	7.00%	7.00%	7.00%	7.00%
Depreciation differences	0.00%	(1.00%)	0.00%	(1.00%)
Other permanent items			0.00%	0.00%
Effective income tax rate	24.00%	25.00%	24.00%	25.00%

Supplemental Information (Cash and Cash Equivalents) (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023	Dec. 31, 2022
Schedule of Cash and Cash Equivalents Including Restricted Cash [Line Items]
Cash and cash equivalents	$ 19	$ 25
Restricted cash included in “Other current assets”	18	13
Restricted cash included in “Other assets”	260	229
Restricted cash included in “Nuclear decommissioning trust fund”	4	5
Total cash, cash equivalents, and restricted cash	301	272	$ 246	$ 216
Union Electric 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”	7	5
Restricted cash included in “Other assets”	0	0
Restricted cash included in “Nuclear decommissioning trust fund”	4	5
Total cash, cash equivalents, and restricted cash	11	10	8	13
Ameren Illinois Company
Schedule of Cash and Cash Equivalents Including Restricted Cash [Line Items]
Cash and cash equivalents	6	0
Restricted cash included in “Other current assets”	7	5
Restricted cash included in “Other assets”	260	229
Restricted cash included in “Nuclear decommissioning trust fund”	0	0
Total cash, cash equivalents, and restricted cash	$ 273	$ 234	$ 229	$ 191

Supplemental Information (Allowance for Doubtful Accounts) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Allowance for Doubtful Accounts Receivable [Roll Forward]
Beginning of period	$ 37	$ 34	$ 30	$ 31
Bad debt expense	6	13	16	23
Charged to other accounts	1	1	4	1
Net write-offs	(7)	(9)	(13)	(16)
End of period	37	39	37	39
Payables for purchased receivables	49		49		$ 42
Union Electric Company
Allowance for Doubtful Accounts Receivable [Roll Forward]
Beginning of period	11	12	12	13
Bad debt expense	4	2	5	4
Net write-offs	(3)	(2)	(5)	(5)
End of period	12	12	12	12
Ameren Illinois Company
Allowance for Doubtful Accounts Receivable [Roll Forward]
Beginning of period	26	22	18	18
Bad debt expense	2	11	11	19
Charged to other accounts	1	1	4	1
Net write-offs	(4)	(7)	(8)	(11)
End of period	25	$ 27	25	$ 27
Payables for purchased receivables	$ 49		$ 49		$ 42

Supplemental Information (Supplemental Cash Flow Information) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Supplemental Cash Flow Information [Line Items]
Accrued capital expenditures, including nuclear fuel expenditures	$ 380	$ 325
Net realized and unrealized gain – nuclear decommissioning trust fund	103	105
Return on investment in industrial development revenue bonds	0	240
Termination of a financing obligation	0	240
Issuance of common stock for stock-based compensation
Supplemental Cash Flow Information [Line Items]
Stock Issued	16	37
Issuance of common stock under the DRPlus
Supplemental Cash Flow Information [Line Items]
Stock Issued	7	7
Union Electric Company
Supplemental Cash Flow Information [Line Items]
Accrued capital expenditures, including nuclear fuel expenditures	232	132
Net realized and unrealized gain – nuclear decommissioning trust fund	103	105
Return on investment in industrial development revenue bonds	0	240
Termination of a financing obligation	0	240
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, including nuclear fuel expenditures	134	173
Net realized and unrealized gain – nuclear decommissioning trust fund	0	0
Return on investment in industrial development revenue bonds	0	0
Termination of a financing obligation	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 (Schedule of Asset Retirement Obligations) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Dec. 31, 2023
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Beginning Balance	$ 791
Liabilities incurred	7
Liabilities settled	(5)
Accretion	17
Asset Retirement Obligation, Ending Balance	810
Other current liabilities	655	$ 501
Union Electric Company
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Beginning Balance	787
Liabilities incurred	7
Liabilities settled	(4)
Accretion	17
Asset Retirement Obligation, Ending Balance	807
Other current liabilities	234	153
Ameren Illinois Company
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Beginning Balance	4
Liabilities incurred	0
Liabilities settled	(1)
Accretion	0
Asset Retirement Obligation, Ending Balance	3
Other current liabilities	219	263
Asset Retirement Obligation Balance
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Other current liabilities	19	19
Asset Retirement Obligation Balance \| Union Electric Company
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Other current liabilities	$ 19	$ 19

Supplemental Information (Narrative) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Effective Income Tax Rate Reconciliation, Share-based Compensation, Excess Tax Benefit, Amount	$ 1	$ (6)
Deferred Compensation Liability, Classified, Noncurrent	$ 80		$ 85
Q1 2024 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 2024 Issuance
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)	359,133
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Granted in Period, Fair Value	$ 21
Stock Issued During Period Percentage Conversion Of Units, Low End	0.00%
Stock Issued During Period Percentage Conversion Of Units, High End	200.00%
Performance Shares \| Market performance measures achievement \| Q1 2024 Issuance
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)	307,816
Performance Shares \| Renewable generation and energy storage installation targets \| Q1 2024 Issuance
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)	51,317
Restricted Stock Units (RSUs) \| Q1 2024 Issuance
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)	153,887
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Granted in Period, Fair Value	$ 11

Supplemental Information (Schedule Of Excise Taxes) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Accounting Policies [Line Items]
Excise tax expense	$ 69	$ 65	$ 141	$ 136
Union Electric Company
Accounting Policies [Line Items]
Excise tax expense	41	39	76	73
Ameren Illinois Company
Accounting Policies [Line Items]
Excise tax expense	$ 28	$ 26	$ 65	$ 63

Supplemental Information (Earnings Per Share) (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Earnings Per Share Reconciliation [Abstract]
Weighted-average Common Shares Outstanding – Basic	266,700,000	262,600,000	266,500,000	262,400,000
Assumed settlement of performance share units and restricted stock units	100,000	600,000	300,000	800,000
Weighted-average Common Shares Outstanding – Diluted	266,800,000	263,200,000	266,800,000	263,200,000
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in shares)	0	0	0	0

Segment Information (Schedule Of Segment Reporting Information By Segment) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Segment Reporting Information [Line Items]
Operating Revenues	$ 1,693	$ 1,760	$ 3,509	$ 3,822
Net income (loss) attributable to common shareholders	258	237	519	501
Capital expenditures	1,002	891	1,892	1,822
Union Electric Company
Segment Reporting Information [Line Items]
Operating Revenues	888	941	1,663	1,864
Net Income (Loss)	128	102	153	130
Ameren Illinois Company
Segment Reporting Information [Line Items]
Operating Revenues	766	779	1,766	1,880
Net Income (Loss)	124	129	339	327
Capital expenditures	344	437	717	844
Operating Segments \| Union Electric Company
Segment Reporting Information [Line Items]
Operating Revenues	879	933	1,647	1,846
Net Income (Loss)	128	102	153	130
Capital expenditures	638	433	1,104	914
Operating Segments \| Ameren Illinois Electric Distribution
Segment Reporting Information [Line Items]
Operating Revenues	509	540	1,015	1,164
Net Income (Loss)	61	66	117	127
Capital expenditures	132	180	316	350
Operating Segments \| Ameren Illinois Natural Gas
Segment Reporting Information [Line Items]
Operating Revenues	148	152	539	543
Net Income (Loss)	6	11	112	98
Capital expenditures	59	90	119	141
Operating Segments \| Ameren Transmission
Segment Reporting Information [Line Items]
Operating Revenues	157	135	308	269
Net Income (Loss)	79	72	151	143
Capital expenditures	175	197	341	410
Operating Segments \| Ameren Illinois Company \| Ameren Illinois Electric Distribution
Segment Reporting Information [Line Items]
Operating Revenues	509	540	1,015	1,164
Net Income (Loss)	61	66	117	127
Capital expenditures	132	180	316	350
Operating Segments \| Ameren Illinois Company \| Ameren Illinois Natural Gas
Segment Reporting Information [Line Items]
Operating Revenues	148	152	539	543
Net Income (Loss)	6	11	112	98
Capital expenditures	59	90	119	141
Operating Segments \| Ameren Illinois Company \| Ameren Illinois Transmission
Segment Reporting Information [Line Items]
Operating Revenues	109	87	212	173
Net Income (Loss)	57	52	110	102
Capital expenditures	153	167	282	353
Other
Segment Reporting Information [Line Items]
Net Income (Loss)	(16)	(14)	(14)	3
Capital expenditures	2	2	4	5
Intersegment Eliminations
Segment Reporting Information [Line Items]
Intersegment revenues	(43)	(34)	(84)	(73)
Capital expenditures	(4)	(11)	8	2
Intersegment Eliminations \| Union Electric Company
Segment Reporting Information [Line Items]
Intersegment revenues	(9)	(8)	(16)	(18)
Intersegment Eliminations \| Ameren Illinois Electric Distribution
Segment Reporting Information [Line Items]
Intersegment revenues	0	0	0	0
Intersegment Eliminations \| Ameren Illinois Natural Gas
Segment Reporting Information [Line Items]
Intersegment revenues	0	0	0	0
Intersegment Eliminations \| Ameren Transmission
Segment Reporting Information [Line Items]
Intersegment revenues	(34)	(26)	(68)	(55)
Intersegment Eliminations \| Ameren Illinois Company
Segment Reporting Information [Line Items]
Intersegment revenues	(27)	(26)	(55)	(54)
Intersegment Eliminations \| Ameren Illinois Company \| Ameren Illinois Electric Distribution
Segment Reporting Information [Line Items]
Intersegment revenues	0	0	0	0
Intersegment Eliminations \| Ameren Illinois Company \| Ameren Illinois Natural Gas
Segment Reporting Information [Line Items]
Intersegment revenues	0	0	0	0
Intersegment Eliminations \| Ameren Illinois Company \| Ameren Illinois Transmission
Segment Reporting Information [Line Items]
Intersegment revenues	$ (27)	$ (26)	$ (55)	$ (54)

Segment Information (Disaggregation of Revenue) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Disaggregation of Revenue [Line Items]
Operating Revenues	$ 1,693	$ 1,760	$ 3,509	$ 3,822
Revenues	1,693	1,760	3,509	3,822
Revenues from alternative revenue programs	25	74	86	172
Other revenues not from contracts with customers	3	1	7	(2)
Union Electric Company
Disaggregation of Revenue [Line Items]
Revenues from alternative revenue programs	(1)	0	(7)	(2)
Other revenues not from contracts with customers	1	(2)	2	(8)
Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues from alternative revenue programs	22	60	61	124
Other revenues not from contracts with customers	1	2	3	4
Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues from alternative revenue programs	0	9	19	37
Other revenues not from contracts with customers	1	1	2	2
Ameren Transmission
Disaggregation of Revenue [Line Items]
Revenues from alternative revenue programs	4	5	13	13
Other revenues not from contracts with customers	0	0	0	0
Electric
Disaggregation of Revenue [Line Items]
Operating Revenues	1,521	1,585	2,885	3,175
Revenues	1,521	1,585	2,885	3,175
Electric \| Residential
Disaggregation of Revenue [Line Items]
Operating Revenues	706	697	1,344	1,403
Electric \| Commercial
Disaggregation of Revenue [Line Items]
Operating Revenues	487	504	911	951
Electric \| Industrial
Disaggregation of Revenue [Line Items]
Operating Revenues	124	123	230	232
Electric \| Other
Disaggregation of Revenue [Line Items]
Revenues	204	261	400	589
Natural gas
Disaggregation of Revenue [Line Items]
Operating Revenues	172	175	624	647
Revenues	172	175	624	647
Natural gas \| Residential
Disaggregation of Revenue [Line Items]
Operating Revenues	115	111	442	459
Natural gas \| Commercial
Disaggregation of Revenue [Line Items]
Operating Revenues	29	31	113	131
Natural gas \| Industrial
Disaggregation of Revenue [Line Items]
Operating Revenues	2	3	8	12
Natural gas \| Other
Disaggregation of Revenue [Line Items]
Revenues	26	30	61	45
Ameren Illinois Company
Disaggregation of Revenue [Line Items]
Operating Revenues	766	779	1,766	1,880
Revenues	766	779	1,766	1,880
Revenues from alternative revenue programs	24	72	90	171
Other revenues not from contracts with customers	2	3	5	6
Ameren Illinois Company \| Residential
Disaggregation of Revenue [Line Items]
Operating Revenues	413	435	997	1,113
Ameren Illinois Company \| Commercial
Disaggregation of Revenue [Line Items]
Operating Revenues	187	218	420	495
Ameren Illinois Company \| Industrial
Disaggregation of Revenue [Line Items]
Operating Revenues	48	50	97	105
Ameren Illinois Company \| Other
Disaggregation of Revenue [Line Items]
Revenues	118	76	252	167
Ameren Illinois Company \| Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues from alternative revenue programs	22	60	61	124
Other revenues not from contracts with customers	1	2	3	4
Ameren Illinois Company \| Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues from alternative revenue programs	0	9	19	37
Other revenues not from contracts with customers	1	1	2	2
Ameren Illinois Company \| Ameren Illinois Transmission
Disaggregation of Revenue [Line Items]
Revenues from alternative revenue programs	2	3	10	10
Other revenues not from contracts with customers	0	0	0	0
Ameren Illinois Company \| Electric
Disaggregation of Revenue [Line Items]
Operating Revenues	618	627	1,227	1,337
Ameren Illinois Company \| Natural gas
Disaggregation of Revenue [Line Items]
Operating Revenues	148	152	539	543
Operating Segments \| Union Electric Company
Disaggregation of Revenue [Line Items]
Operating Revenues	879	933	1,647	1,846
Revenues	888	941	1,663	1,864
Operating Segments \| Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Operating Revenues	509	540	1,015	1,164
Revenues	509	540	1,015	1,164
Operating Segments \| Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Operating Revenues	148	152	539	543
Revenues	148	152	539	543
Operating Segments \| Ameren Transmission
Disaggregation of Revenue [Line Items]
Operating Revenues	157	135	308	269
Revenues	191	161	376	324
Operating Segments \| Electric \| Union Electric Company
Disaggregation of Revenue [Line Items]
Revenues	864	918	1,578	1,759
Operating Segments \| Electric \| Union Electric Company \| Residential
Disaggregation of Revenue [Line Items]
Operating Revenues	395	360	736	684
Operating Segments \| Electric \| Union Electric Company \| Commercial
Disaggregation of Revenue [Line Items]
Operating Revenues	324	311	583	558
Operating Segments \| Electric \| Union Electric Company \| Industrial
Disaggregation of Revenue [Line Items]
Operating Revenues	77	75	138	136
Operating Segments \| Electric \| Union Electric Company \| Other
Disaggregation of Revenue [Line Items]
Revenues	68	172	121	381
Operating Segments \| Electric \| Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues	509	540	1,015	1,164
Operating Segments \| Electric \| Ameren Illinois Electric Distribution \| Residential
Disaggregation of Revenue [Line Items]
Operating Revenues	311	337	608	719
Operating Segments \| Electric \| Ameren Illinois Electric Distribution \| Commercial
Disaggregation of Revenue [Line Items]
Operating Revenues	163	193	328	393
Operating Segments \| Electric \| Ameren Illinois Electric Distribution \| Industrial
Disaggregation of Revenue [Line Items]
Operating Revenues	47	48	92	96
Operating Segments \| Electric \| Ameren Illinois Electric Distribution \| Other
Disaggregation of Revenue [Line Items]
Revenues	(12)	(38)	(13)	(44)
Operating Segments \| Electric \| Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments \| Electric \| Ameren Illinois Natural Gas \| Residential
Disaggregation of Revenue [Line Items]
Operating Revenues	0	0	0	0
Operating Segments \| Electric \| Ameren Illinois Natural Gas \| Commercial
Disaggregation of Revenue [Line Items]
Operating Revenues	0	0	0	0
Operating Segments \| Electric \| Ameren Illinois Natural Gas \| Industrial
Disaggregation of Revenue [Line Items]
Operating Revenues	0	0	0	0
Operating Segments \| Electric \| Ameren Illinois Natural Gas \| Other
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments \| Electric \| Ameren Transmission
Disaggregation of Revenue [Line Items]
Revenues	191	161	376	324
Operating Segments \| Electric \| Ameren Transmission \| Residential
Disaggregation of Revenue [Line Items]
Operating Revenues	0	0	0	0
Operating Segments \| Electric \| Ameren Transmission \| Commercial
Disaggregation of Revenue [Line Items]
Operating Revenues	0	0	0	0
Operating Segments \| Electric \| Ameren Transmission \| Industrial
Disaggregation of Revenue [Line Items]
Operating Revenues	0	0	0	0
Operating Segments \| Electric \| Ameren Transmission \| Other
Disaggregation of Revenue [Line Items]
Revenues	191	161	376	324
Operating Segments \| Natural gas \| Union Electric Company
Disaggregation of Revenue [Line Items]
Revenues	24	23	85	105
Operating Segments \| Natural gas \| Union Electric Company \| Residential
Disaggregation of Revenue [Line Items]
Operating Revenues	13	13	53	65
Operating Segments \| Natural gas \| Union Electric Company \| Commercial
Disaggregation of Revenue [Line Items]
Operating Revenues	5	6	21	29
Operating Segments \| Natural gas \| Union Electric Company \| Industrial
Disaggregation of Revenue [Line Items]
Operating Revenues	1	1	3	3
Operating Segments \| Natural gas \| Union Electric Company \| Other
Disaggregation of Revenue [Line Items]
Revenues	5	3	8	8
Operating Segments \| Natural gas \| Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments \| Natural gas \| Ameren Illinois Electric Distribution \| Residential
Disaggregation of Revenue [Line Items]
Operating Revenues	0	0	0	0
Operating Segments \| Natural gas \| Ameren Illinois Electric Distribution \| Commercial
Disaggregation of Revenue [Line Items]
Operating Revenues	0	0	0	0
Operating Segments \| Natural gas \| Ameren Illinois Electric Distribution \| Industrial
Disaggregation of Revenue [Line Items]
Operating Revenues	0	0	0	0
Operating Segments \| Natural gas \| Ameren Illinois Electric Distribution \| Other
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments \| Natural gas \| Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues	148	152	539	543
Operating Segments \| Natural gas \| Ameren Illinois Natural Gas \| Residential
Disaggregation of Revenue [Line Items]
Operating Revenues	102	98	389	394
Operating Segments \| Natural gas \| Ameren Illinois Natural Gas \| Commercial
Disaggregation of Revenue [Line Items]
Operating Revenues	24	25	92	102
Operating Segments \| Natural gas \| Ameren Illinois Natural Gas \| Industrial
Disaggregation of Revenue [Line Items]
Operating Revenues	1	2	5	9
Operating Segments \| Natural gas \| Ameren Illinois Natural Gas \| Other
Disaggregation of Revenue [Line Items]
Revenues	21	27	53	38
Operating Segments \| Natural gas \| Ameren Transmission
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments \| Natural gas \| Ameren Transmission \| Residential
Disaggregation of Revenue [Line Items]
Operating Revenues	0	0	0	0
Operating Segments \| Natural gas \| Ameren Transmission \| Commercial
Disaggregation of Revenue [Line Items]
Operating Revenues	0	0	0	0
Operating Segments \| Natural gas \| Ameren Transmission \| Industrial
Disaggregation of Revenue [Line Items]
Operating Revenues	0	0	0	0
Operating Segments \| Natural gas \| Ameren Transmission \| Other
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments \| Ameren Illinois Company \| Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Operating Revenues	509	540	1,015	1,164
Operating Segments \| Ameren Illinois Company \| Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Operating Revenues	148	152	539	543
Operating Segments \| Ameren Illinois Company \| Ameren Illinois Transmission
Disaggregation of Revenue [Line Items]
Operating Revenues	109	87	212	173
Operating Segments \| Ameren Illinois Company \| Electric \| Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues	509	540	1,015	1,164
Operating Segments \| Ameren Illinois Company \| Electric \| Ameren Illinois Electric Distribution \| Residential
Disaggregation of Revenue [Line Items]
Operating Revenues	311	337	608	719
Operating Segments \| Ameren Illinois Company \| Electric \| Ameren Illinois Electric Distribution \| Commercial
Disaggregation of Revenue [Line Items]
Operating Revenues	163	193	328	393
Operating Segments \| Ameren Illinois Company \| Electric \| Ameren Illinois Electric Distribution \| Industrial
Disaggregation of Revenue [Line Items]
Operating Revenues	47	48	92	96
Operating Segments \| Ameren Illinois Company \| Electric \| Ameren Illinois Electric Distribution \| Other
Disaggregation of Revenue [Line Items]
Revenues	(12)	(38)	(13)	(44)
Operating Segments \| Ameren Illinois Company \| Electric \| Ameren Illinois Transmission
Disaggregation of Revenue [Line Items]
Revenues	136	113	267	227
Operating Segments \| Ameren Illinois Company \| Electric \| Ameren Illinois Transmission \| Residential
Disaggregation of Revenue [Line Items]
Operating Revenues	0	0	0	0
Operating Segments \| Ameren Illinois Company \| Electric \| Ameren Illinois Transmission \| Commercial
Disaggregation of Revenue [Line Items]
Operating Revenues	0	0	0	0
Operating Segments \| Ameren Illinois Company \| Electric \| Ameren Illinois Transmission \| Industrial
Disaggregation of Revenue [Line Items]
Operating Revenues	0	0	0	0
Operating Segments \| Ameren Illinois Company \| Electric \| Ameren Illinois Transmission \| Other
Disaggregation of Revenue [Line Items]
Revenues	136	113	267	227
Operating Segments \| Ameren Illinois Company \| Natural gas \| Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues	148	152	539	543
Operating Segments \| Ameren Illinois Company \| Natural gas \| Ameren Illinois Natural Gas \| Residential
Disaggregation of Revenue [Line Items]
Operating Revenues	102	98	389	394
Operating Segments \| Ameren Illinois Company \| Natural gas \| Ameren Illinois Natural Gas \| Commercial
Disaggregation of Revenue [Line Items]
Operating Revenues	24	25	92	102
Operating Segments \| Ameren Illinois Company \| Natural gas \| Ameren Illinois Natural Gas \| Industrial
Disaggregation of Revenue [Line Items]
Operating Revenues	1	2	5	9
Operating Segments \| Ameren Illinois Company \| Natural gas \| Ameren Illinois Natural Gas \| Other
Disaggregation of Revenue [Line Items]
Revenues	21	27	53	38
Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Revenues	(43)	(34)	(84)	(73)
Revenues	(43)	(34)	(84)	(73)
Intersegment Eliminations \| Union Electric Company
Disaggregation of Revenue [Line Items]
Revenues	(9)	(8)	(16)	(18)
Intersegment Eliminations \| Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations \| Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations \| Ameren Transmission
Disaggregation of Revenue [Line Items]
Revenues	(34)	(26)	(68)	(55)
Intersegment Eliminations \| Electric
Disaggregation of Revenue [Line Items]
Revenues	(43)	(34)	(84)	(72)
Intersegment Eliminations \| Electric \| Residential
Disaggregation of Revenue [Line Items]
Operating Revenues	0	0	0	0
Intersegment Eliminations \| Electric \| Commercial
Disaggregation of Revenue [Line Items]
Operating Revenues	0	0	0	0
Intersegment Eliminations \| Electric \| Industrial
Disaggregation of Revenue [Line Items]
Operating Revenues	0	0	0	0
Intersegment Eliminations \| Electric \| Other
Disaggregation of Revenue [Line Items]
Revenues	(43)	(34)	(84)	(72)
Intersegment Eliminations \| Natural gas
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	(1)
Intersegment Eliminations \| Natural gas \| Residential
Disaggregation of Revenue [Line Items]
Operating Revenues	0	0	0	0
Intersegment Eliminations \| Natural gas \| Commercial
Disaggregation of Revenue [Line Items]
Operating Revenues	0	0	0	0
Intersegment Eliminations \| Natural gas \| Industrial
Disaggregation of Revenue [Line Items]
Operating Revenues	0	0	0	0
Intersegment Eliminations \| Natural gas \| Other
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	(1)
Intersegment Eliminations \| Ameren Illinois Company
Disaggregation of Revenue [Line Items]
Revenues	(27)	(26)	(55)	(54)
Revenues	(27)	(26)	(55)	(54)
Intersegment Eliminations \| Ameren Illinois Company \| Residential
Disaggregation of Revenue [Line Items]
Operating Revenues	0	0	0	0
Intersegment Eliminations \| Ameren Illinois Company \| Commercial
Disaggregation of Revenue [Line Items]
Operating Revenues	0	0	0	0
Intersegment Eliminations \| Ameren Illinois Company \| Industrial
Disaggregation of Revenue [Line Items]
Operating Revenues	0	0	0	0
Intersegment Eliminations \| Ameren Illinois Company \| Other
Disaggregation of Revenue [Line Items]
Revenues	(27)	(26)	(55)	(54)
Intersegment Eliminations \| Ameren Illinois Company \| Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations \| Ameren Illinois Company \| Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations \| Ameren Illinois Company \| Ameren Illinois Transmission
Disaggregation of Revenue [Line Items]
Revenues	$ (27)	$ (26)	$ (55)	$ (54)