Consolidated Statement of Income (Loss) and Comprehensive Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Operating Revenues:
Total operating revenues	$ 2,060	$ 2,306	$ 5,882	$ 5,911
Operating Expenses:
Fuel	158	117	423	376
Purchased Power	272	563	1,095	1,058
Natural gas purchased for resale	30	58	280	431
Other operations and maintenance	470	475	1,368	1,427
Depreciation and amortization	369	350	1,024	965
Taxes other than income taxes	147	144	398	415
Total operating expenses	1,446	1,707	4,588	4,672
Operating Income	614	599	1,294	1,239
Other Income, Net	101	58	261	180
Interest Charges	152	126	413	356
Income Before Income Taxes	563	531	1,142	1,063
Income Taxes	69	78	144	148
Net Income	494	453	998	915
Less: Net Income Attributable to Noncontrolling Interests	1	1	4	4
Net Income Attributable to Ameren Common Shareholders	493	452	994	911
Pension and other postretirement benefit plan activity, net of income taxes (benefit)	(1)	0	(3)	1
Comprehensive Income	493	453	995	916
Less: Comprehensive Income Attributable to Noncontrolling Interests	1	1	4	4
Comprehensive Income Attributable to Ameren Common Shareholders	$ 492	$ 452	$ 991	$ 912
Earnings Per Share, Basic [Abstract]
Earnings per Common Share – Basic	$ 1.88	$ 1.75	$ 3.79	$ 3.53
Earnings Per Share, Diluted [Abstract]
Earnings per Common Share – Diluted	$ 1.87	$ 1.74	$ 3.78	$ 3.51
Weighted-average Common Shares Outstanding – Basic	262.8	258.4	262.5	258.2
Weighted-average Common Shares Outstanding – Diluted	263.4	259.5	263.2	259.3
Electric
Operating Revenues:
Total operating revenues	$ 1,921	$ 2,140	$ 5,096	$ 4,971
Natural gas
Operating Revenues:
Total operating revenues	139	166	786	940
Union Electric Company
Operating Revenues:
Total operating revenues	1,237	1,359	3,101	3,096
Operating Expenses:
Fuel	158	117	423	376
Purchased Power	75	247	420	458
Natural gas purchased for resale	4	7	60	65
Other operations and maintenance	256	252	732	744
Depreciation and amortization	217	208	579	550
Taxes other than income taxes	108	106	276	281
Total operating expenses	818	937	2,490	2,474
Operating Income	419	422	611	622
Other Income, Net	44	25	85	72
Interest Charges	63	58	166	157
Income Before Income Taxes	400	389	530	537
Income Taxes	(12)	(9)	(14)	(13)
Net Income	412	398	544	550
Preferred Stock Dividends	1	1	3	3
Net Income Attributable to Parent	411	397	541	547
Union Electric Company | Electric
Operating Revenues:
Total operating revenues	1,219	1,338	2,978	2,966
Union Electric Company | Natural gas
Operating Revenues:
Total operating revenues	18	21	123	130
Ameren Illinois Company
Operating Revenues:
Total operating revenues	783	904	2,663	2,697
Operating Expenses:
Purchased Power	200	319	679	608
Natural gas purchased for resale	26	51	220	366
Other operations and maintenance	200	215	603	663
Depreciation and amortization	139	130	410	382
Taxes other than income taxes	34	34	108	122
Total operating expenses	599	749	2,020	2,141
Operating Income	184	155	643	556
Other Income, Net	37	26	115	75
Interest Charges	54	42	151	125
Income Before Income Taxes	167	139	607	506
Income Taxes	42	36	154	130
Net Income	125	103	453	376
Preferred Stock Dividends	0	0	1	1
Net Income Attributable to Parent	125	103	452	375
Ameren Illinois Company | Electric
Operating Revenues:
Total operating revenues	661	758	1,998	1,886
Ameren Illinois Company | Natural gas
Operating Revenues:
Total operating revenues	$ 122	$ 146	$ 665	$ 811