Supplemental Information (Supplemental Cash Flow Information) (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2023	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Supplemental Cash Flow Information [Line Items]
Accrued capital expenditures		$ 480	$ 518	$ 441
Net realized and unrealized gain (loss) – nuclear decommissioning trust fund		165	167	(218)
Return on investment in industrial development revenue bonds		0	240	0
Stock Issued			40
Termination of a financing obligation		0	240	0
Issuance of common stock for stock-based compensation
Supplemental Cash Flow Information [Line Items]
Stock Issued		16	40	31
Issuance of common stock under the DRPlus
Supplemental Cash Flow Information [Line Items]
Stock Issued		7	7	8
Ameren Missouri
Supplemental Cash Flow Information [Line Items]
Accrued capital expenditures		303	270	243
Net realized and unrealized gain (loss) – nuclear decommissioning trust fund		165	167	(218)
Return on investment in industrial development revenue bonds		0	240	0
Termination of a financing obligation	$ 240	0	240	0
Ameren Missouri | Issuance of common stock for stock-based compensation
Supplemental Cash Flow Information [Line Items]
Stock Issued		0	0	0
Ameren Missouri | Issuance of common stock under the DRPlus
Supplemental Cash Flow Information [Line Items]
Stock Issued		0	0	0
Ameren Illinois
Supplemental Cash Flow Information [Line Items]
Accrued capital expenditures		157	212	181
Net realized and unrealized gain (loss) – nuclear decommissioning trust fund		0	0	0
Return on investment in industrial development revenue bonds		0	0	0
Termination of a financing obligation		0	0	0
Ameren Illinois | Issuance of common stock for stock-based compensation
Supplemental Cash Flow Information [Line Items]
Stock Issued		0	0	0
Ameren Illinois | Issuance of common stock under the DRPlus
Supplemental Cash Flow Information [Line Items]
Stock Issued		$ 0	$ 0	$ 0