Consolidated Statement of Income (Loss) and Comprehensive Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Operating Revenues:
Total operating revenues	$ 2,173	$ 2,060	$ 5,682	$ 5,882
Operating Expenses:
Fuel and purchased power	499	430	1,154	1,518
Natural gas purchased for resale	30	30	214	280
Other operations and maintenance	520	470	1,455	1,368
Depreciation and amortization	388	369	1,125	1,024
Taxes other than income taxes	150	147	416	398
Total operating expenses	1,587	1,446	4,364	4,588
Operating Income	586	614	1,318	1,294
Other Income, Net	101	101	293	261
Interest Charges	173	152	492	413
Income Before Income Taxes	514	563	1,119	1,142
Income Taxes	57	69	140	144
Net Income	457	494	979	998
Less: Net Income Attributable to Noncontrolling Interests	1	1	4	4
Net Income Attributable to Ameren Common Shareholders	456	493	975	994
Pension and other postretirement benefit plan activity, net of income taxes (benefit)	(1)	(1)	(4)	(3)
Comprehensive Income	456	493	975	995
Less: Comprehensive Income Attributable to Noncontrolling Interests	1	1	4	4
Comprehensive Income Attributable to Ameren Common Shareholders	$ 455	$ 492	$ 971	$ 991
Earnings Per Share, Basic [Abstract]
Earnings per Common Share – Basic	$ 1.71	$ 1.88	$ 3.66	$ 3.79
Earnings Per Share, Diluted [Abstract]
Earnings per Common Share – Diluted	$ 1.70	$ 1.87	$ 3.65	$ 3.78
Weighted-average Common Shares Outstanding – Basic	266.8	262.8	266.6	262.5
Weighted-average Common Shares Outstanding – Diluted	267.3	263.4	266.9	263.2
Electric
Operating Revenues:
Total operating revenues	$ 2,035	$ 1,921	$ 4,920	$ 5,096
Natural gas
Operating Revenues:
Total operating revenues	138	139	762	786
Union Electric Company
Operating Revenues:
Total operating revenues	1,342	1,237	3,005	3,101
Operating Expenses:
Fuel and purchased power	334	233	689	843
Natural gas purchased for resale	4	4	41	60
Other operations and maintenance	288	256	789	732
Depreciation and amortization	220	217	623	579
Taxes other than income taxes	109	108	287	276
Total operating expenses	955	818	2,429	2,490
Operating Income	387	419	576	611
Other Income, Net	51	44	144	85
Interest Charges	62	63	187	166
Income Before Income Taxes	376	400	533	530
Income Taxes	(6)	(12)	(4)	(14)
Net Income	382	412	537	544
Preferred Stock Dividends	1	1	3	3
Net Income Available to Common Shareholder	381	411	534	541
Union Electric Company | Electric
Operating Revenues:
Total operating revenues	1,324	1,219	2,902	2,978
Union Electric Company | Natural gas
Operating Revenues:
Total operating revenues	18	18	103	123
Ameren Illinois Company
Operating Revenues:
Total operating revenues	793	783	2,559	2,663
Operating Expenses:
Purchased Power	169	200	474	679
Natural gas purchased for resale	26	26	173	220
Other operations and maintenance	229	200	663	603
Depreciation and amortization	155	139	462	410
Taxes other than income taxes	37	34	116	108
Total operating expenses	616	599	1,888	2,020
Operating Income	177	184	671	643
Other Income, Net	37	37	105	115
Interest Charges	63	54	178	151
Income Before Income Taxes	151	167	598	607
Income Taxes	37	42	144	154
Net Income	114	125	454	453
Preferred Stock Dividends	0	0	1	1
Net Income Available to Common Shareholder	114	125	453	452
Ameren Illinois Company | Electric
Operating Revenues:
Total operating revenues	672	661	1,899	1,998
Ameren Illinois Company | Natural gas
Operating Revenues:
Total operating revenues	$ 121	$ 122	$ 660	$ 665