Consolidated Statement of Income (Loss) and Comprehensive Income - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Operating Revenues:
Total operating revenues	$ 1,816	$ 2,062
Operating Expenses:
Fuel and purchased power	328	608
Natural gas purchased for resale	151	208
Other operations and maintenance	470	448
Depreciation and amortization	361	320
Taxes other than income taxes	135	127
Total operating expenses	1,445	1,711
Operating Income	371	351
Other Income, Net	89	78
Interest Charges	154	127
Income Before Income Taxes	306	302
Income Taxes	44	37
Net Income	262	265
Less: Net Income Attributable to Noncontrolling Interests	1	1
Net Income Attributable to Ameren Common Shareholders	261	264
Pension and other postretirement benefit plan activity, net of income taxes (benefit)	(1)	(1)
Comprehensive Income	261	264
Less: Comprehensive Income Attributable to Noncontrolling Interests	1	1
Comprehensive Income Attributable to Ameren Common Shareholders	$ 260	$ 263
Earnings Per Share, Basic [Abstract]
Earnings per Common Share – Basic	$ 0.98	$ 1.01
Earnings Per Share, Diluted [Abstract]
Earnings per Common Share – Diluted	$ 0.98	$ 1.00
Weighted-average Common Shares Outstanding – Basic	266.4	262.2
Weighted-average Common Shares Outstanding – Diluted	266.8	263.1
Electric
Operating Revenues:
Total operating revenues	$ 1,364	$ 1,590
Natural gas
Operating Revenues:
Total operating revenues	452	472
Union Electric Company
Operating Revenues:
Total operating revenues	775	923
Operating Expenses:
Fuel and purchased power	166	321
Natural gas purchased for resale	28	47
Other operations and maintenance	254	239
Depreciation and amortization	195	176
Taxes other than income taxes	87	80
Total operating expenses	730	863
Operating Income	45	60
Other Income, Net	44	19
Interest Charges	62	51
Income Before Income Taxes	27	28
Income Taxes	1	(1)
Net Income	26	29
Preferred Stock Dividends	1	1
Net Income Attributable to Parent	25	28
Union Electric Company | Electric
Operating Revenues:
Total operating revenues	714	841
Union Electric Company | Natural gas
Operating Revenues:
Total operating revenues	61	82
Ameren Illinois Company
Operating Revenues:
Total operating revenues	1,000	1,101
Operating Expenses:
Purchased Power	164	287
Natural gas purchased for resale	123	161
Other operations and maintenance	210	202
Depreciation and amortization	153	133
Taxes other than income taxes	44	42
Total operating expenses	694	825
Operating Income	306	276
Other Income, Net	31	37
Interest Charges	55	47
Income Before Income Taxes	282	266
Income Taxes	67	68
Net Income	215	198
Net Income Attributable to Parent	215	198
Ameren Illinois Company | Electric
Operating Revenues:
Total operating revenues	609	710
Ameren Illinois Company | Natural gas
Operating Revenues:
Total operating revenues	$ 391	$ 391