Consolidated Statement of Income (Loss) and Comprehensive Income - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Operating Revenues:
Total operating revenues	$ 2,062	$ 1,879
Operating Expenses:
Fuel	113	176
Purchased power	495	177
Natural gas purchased for resale	208	293
Other operations and maintenance	448	461
Depreciation and amortization	320	299
Taxes other than income taxes	127	142
Total operating expenses	1,711	1,548
Operating Income	351	331
Other Income, Net	78	60
Interest Charges	127	104
Income Before Income Taxes	302	287
Income Taxes	37	34
Net Income	265	253
Less: Net Income Attributable to Noncontrolling Interests	1	1
Net Income Attributable to Ameren Common Shareholders	264	252
Pension and other postretirement benefit plan activity, net of income taxes (benefit)	(1)	1
Comprehensive Income	264	254
Less: Comprehensive Income Attributable to Noncontrolling Interests	1	1
Comprehensive Income Attributable to Ameren Common Shareholders	$ 263	$ 253
Earnings Per Share, Basic and Diluted [Abstract]
Earnings per Common Share – Basic	$ 1.01	$ 0.98
Earnings per Common Share – Diluted	$ 1.00	$ 0.97
Weighted-average Common Shares Outstanding – Basic	262.2	257.9
Weighted-average Common Shares Outstanding – Diluted	263.1	259.0
Electric
Operating Revenues:
Total operating revenues	$ 1,590	$ 1,318
Natural gas
Operating Revenues:
Total operating revenues	472	561
Union Electric Company
Operating Revenues:
Total operating revenues	923	818
Operating Expenses:
Fuel	113	176
Purchased power	208	50
Natural gas purchased for resale	47	46
Other operations and maintenance	239	232
Depreciation and amortization	176	164
Taxes other than income taxes	80	85
Total operating expenses	863	753
Operating Income	60	65
Other Income, Net	19	23
Interest Charges	51	39
Income Before Income Taxes	28	49
Income Taxes	(1)	(2)
Net Income	29	51
Preferred Stock Dividends	1	1
Net Income Attributable to Parent	28	50
Union Electric Company | Electric
Operating Revenues:
Total operating revenues	841	738
Union Electric Company | Natural gas
Operating Revenues:
Total operating revenues	82	80
Ameren Illinois Company
Operating Revenues:
Total operating revenues	1,101	1,024
Operating Expenses:
Purchased power	287	131
Natural gas purchased for resale	161	247
Other operations and maintenance	202	223
Depreciation and amortization	133	124
Taxes other than income taxes	42	53
Total operating expenses	825	778
Operating Income	276	246
Other Income, Net	37	24
Interest Charges	47	42
Income Before Income Taxes	266	228
Income Taxes	68	59
Net Income	198	169
Net Income Attributable to Parent	198	169
Ameren Illinois Company | Electric
Operating Revenues:
Total operating revenues	710	543
Ameren Illinois Company | Natural gas
Operating Revenues:
Total operating revenues	$ 391	$ 481