Consolidated Statement of Income (Loss) and Comprehensive Income - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Operating Revenues:
Operating Revenues	$ 2,097	$ 1,816
Operating Expenses:
Fuel and purchased power	502	328
Natural gas purchased for resale	169	151
Other operations and maintenance	485	470
Depreciation and amortization	367	361
Taxes other than income taxes	144	135
Total operating expenses	1,667	1,445
Operating Income	430	371
Other Income, Net	85	89
Interest Charges	175	154
Income Before Income Taxes	340	306
Income Taxes	50	44
Net Income	290	262
Less: Net Income Attributable to Noncontrolling Interests	1	1
Preferred Stock Dividends	1	1
Net income attributable to Ameren common shareholders	289	261
Pension and other postretirement benefit plan activity, net of income taxes (benefit) of $— and $—, respectively	0	(1)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax	(4)	0
Comprehensive Income	286	261
Less: Comprehensive Income Attributable to Noncontrolling Interests	1	1
Comprehensive Income Attributable to Ameren Common Shareholders	$ 285	$ 260
Earnings Per Share, Basic [Abstract]
Earnings per Common Share - Basic and Diluted	$ 1.07	$ 0.98
Earnings Per Share, Diluted [Abstract]
Earnings per Common Share - Basic and Diluted	$ 1.07	$ 0.98
Weighted-average Common Shares Outstanding – Basic	270.0	266.4
Weighted-average Common Shares Outstanding – Diluted	271.4	266.8
Electric
Operating Revenues:
Operating Revenues	$ 1,622	$ 1,364
Natural gas
Operating Revenues:
Operating Revenues	475	452
Union Electric Company
Operating Revenues:
Operating Revenues	957	775
Operating Expenses:
Fuel and purchased power	330	166
Natural gas purchased for resale	30	28
Other operations and maintenance	250	254
Depreciation and amortization	194	195
Taxes other than income taxes	89	87
Total operating expenses	893	730
Operating Income	64	45
Other Income, Net	43	44
Interest Charges	60	62
Income Before Income Taxes	47	27
Income Taxes	4	1
Net Income	43	26
Net Income	43	26
Preferred Stock Dividends	1	1
Net income attributable to Ameren common shareholders	42	25
Union Electric Company | Electric
Operating Revenues:
Operating Revenues	893	714
Union Electric Company | Natural gas
Operating Revenues:
Operating Revenues	64	61
Ameren Illinois Company
Operating Revenues:
Operating Revenues	1,100	1,000
Operating Expenses:
Purchased Power	175	164
Natural gas purchased for resale	139	123
Other operations and maintenance	236	210
Depreciation and amortization	159	153
Taxes other than income taxes	51	44
Total operating expenses	760	694
Operating Income	340	306
Other Income, Net	34	31
Interest Charges	62	55
Income Before Income Taxes	312	282
Income Taxes	76	67
Net Income	236	215
Net Income	236	215
Net income attributable to Ameren common shareholders	236	215
Ameren Illinois Company | Electric
Operating Revenues:
Operating Revenues	689	609
Ameren Illinois Company | Natural gas
Operating Revenues:
Operating Revenues	$ 411	$ 391