Consolidated Statement of Income (Loss) and Comprehensive Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Operating Revenues:
Total operating revenues	$ 2,306	$ 1,811	$ 5,911	$ 4,849
Operating Expenses:
Fuel	117	184	376	422
Purchased power	563	159	1,058	479
Natural gas purchased for resale	58	45	431	275
Other operations and maintenance	475	457	1,427	1,289
Depreciation and amortization	350	290	965	856
Taxes other than income taxes	144	142	415	392
Total operating expenses	1,707	1,277	4,672	3,713
Operating Income	599	534	1,239	1,136
Other Income, Net	58	56	180	151
Interest Charges	126	94	356	290
Income Before Income Taxes	531	496	1,063	997
Income Taxes	78	70	148	128
Net Income	453	426	915	869
Less: Net Income Attributable to Noncontrolling Interests	1	1	4	4
Net Income Attributable to Ameren Common Shareholders	452	425	911	865
Pension and other postretirement benefit plan activity, net of income taxes (benefit)	0	1	1	1
Comprehensive Income	453	427	916	870
Less: Comprehensive Income Attributable to Noncontrolling Interests	1	1	4	4
Comprehensive Income Attributable to Ameren Common Shareholders	$ 452	$ 426	$ 912	$ 866
Earnings Per Share, Basic and Diluted [Abstract]
Earnings per Common Share – Basic	$ 1.75	$ 1.66	$ 3.53	$ 3.38
Earnings per Common Share – Diluted	$ 1.74	$ 1.65	$ 3.51	$ 3.36
Weighted-average Common Shares Outstanding – Basic	258.4	257.3	258.2	255.9
Weighted-average Common Shares Outstanding – Diluted	259.5	258.6	259.3	257.2
Electric
Operating Revenues:
Total operating revenues	$ 2,140	$ 1,668	$ 4,971	$ 4,108
Natural gas
Operating Revenues:
Total operating revenues	166	143	940	741
Union Electric Company
Operating Revenues:
Total operating revenues	1,359	1,129	3,096	2,642
Operating Expenses:
Fuel	117	184	376	422
Purchased power	247	57	458	195
Natural gas purchased for resale	7	4	65	40
Other operations and maintenance	252	240	744	683
Depreciation and amortization	208	161	550	474
Taxes other than income taxes	106	104	281	266
Total operating expenses	937	750	2,474	2,080
Operating Income	422	379	622	562
Other Income, Net	25	27	72	74
Interest Charges	58	32	157	107
Income Before Income Taxes	389	374	537	529
Income Taxes	(9)	(2)	(13)	(7)
Net Income	398	376	550	536
Preferred Stock Dividends	1	1	3	3
Net Income Attributable to Parent	397	375	547	533
Union Electric Company | Electric
Operating Revenues:
Total operating revenues	1,338	1,113	2,966	2,543
Union Electric Company | Natural gas
Operating Revenues:
Total operating revenues	21	16	130	99
Ameren Illinois Company
Operating Revenues:
Total operating revenues	904	645	2,697	2,097
Operating Expenses:
Purchased power	319	108	608	298
Natural gas purchased for resale	51	41	366	235
Other operations and maintenance	215	217	663	604
Depreciation and amortization	130	118	382	350
Taxes other than income taxes	34	34	122	114
Total operating expenses	749	518	2,141	1,601
Operating Income	155	127	556	496
Other Income, Net	26	19	75	49
Interest Charges	42	41	125	123
Income Before Income Taxes	139	105	506	422
Income Taxes	36	26	130	107
Net Income	103	79	376	315
Preferred Stock Dividends	0	0	1	1
Net Income Attributable to Parent	103	79	375	314
Ameren Illinois Company | Electric
Operating Revenues:
Total operating revenues	758	518	1,886	1,455
Ameren Illinois Company | Natural gas
Operating Revenues:
Total operating revenues	$ 146	$ 127	$ 811	$ 642