Consolidated Statement of Income (Loss) and Comprehensive Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Operating Revenues:
Total operating revenues	$ 1,726	$ 1,472	$ 3,605	$ 3,038
Operating Expenses:
Fuel	83	173	259	238
Purchased power	318	129	495	320
Natural gas purchased for resale	80	65	373	230
Other operations and maintenance	491	412	952	832
Depreciation and amortization	316	285	615	566
Taxes other than income taxes	129	122	271	250
Total operating expenses	1,417	1,186	2,965	2,436
Operating Income	309	286	640	602
Other Income, Net	62	49	122	95
Interest Charges	126	96	230	196
Income Before Income Taxes	245	239	532	501
Income Taxes	36	31	70	58
Net Income	209	208	462	443
Less: Net Income Attributable to Noncontrolling Interests	2	1	3	3
Net Income Attributable to Ameren Common Shareholders	207	207	459	440
Pension and other postretirement benefit plan activity, net of income taxes (benefit)	0	(1)	1	0
Comprehensive Income	209	207	463	443
Less: Comprehensive Income Attributable to Noncontrolling Interests	2	1	3	3
Comprehensive Income Attributable to Ameren Common Shareholders	$ 207	$ 206	$ 460	$ 440
Earnings Per Share, Basic and Diluted [Abstract]
Earnings per Common Share – Basic	$ 0.80	$ 0.81	$ 1.78	$ 1.72
Earnings per Common Share – Diluted	$ 0.80	$ 0.80	$ 1.77	$ 1.71
Weighted-average Common Shares Outstanding – Basic	258.2	256.1	258.0	255.2
Weighted-average Common Shares Outstanding – Diluted	259.4	257.2	259.2	256.5
Electric
Operating Revenues:
Total operating revenues	$ 1,513	$ 1,284	$ 2,831	$ 2,440
Natural gas
Operating Revenues:
Total operating revenues	213	188	774	598
Union Electric Company
Operating Revenues:
Total operating revenues	919	809	1,737	1,513
Operating Expenses:
Fuel	83	173	259	238
Purchased power	161	50	211	138
Natural gas purchased for resale	12	5	58	36
Other operations and maintenance	260	218	492	443
Depreciation and amortization	178	157	342	313
Taxes other than income taxes	90	85	175	162
Total operating expenses	784	688	1,537	1,330
Operating Income	135	121	200	183
Other Income, Net	24	24	47	47
Interest Charges	60	36	99	75
Income Before Income Taxes	99	109	148	155
Income Taxes	(2)	(3)	(4)	(5)
Net Income	101	112	152	160
Preferred Stock Dividends	1	1	2	2
Net Income Attributable to Parent	100	111	150	158
Union Electric Company | Electric
Operating Revenues:
Total operating revenues	890	789	1,628	1,430
Union Electric Company | Natural gas
Operating Revenues:
Total operating revenues	29	20	109	83
Ameren Illinois Company
Operating Revenues:
Total operating revenues	769	629	1,793	1,452
Operating Expenses:
Purchased power	158	84	289	190
Natural gas purchased for resale	68	60	315	194
Other operations and maintenance	225	193	448	387
Depreciation and amortization	128	117	252	232
Taxes other than income taxes	35	34	88	80
Total operating expenses	614	488	1,392	1,083
Operating Income	155	141	401	369
Other Income, Net	25	16	49	30
Interest Charges	41	40	83	82
Income Before Income Taxes	139	117	367	317
Income Taxes	35	31	94	81
Net Income	104	86	273	236
Preferred Stock Dividends	1	0	1	1
Net Income Attributable to Parent	103	86	272	235
Ameren Illinois Company | Electric
Operating Revenues:
Total operating revenues	585	461	1,128	937
Ameren Illinois Company | Natural gas
Operating Revenues:
Total operating revenues	$ 184	$ 168	$ 665	$ 515