Supplemental Information (Supplemental Cash Flow Information) (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Supplemental Cash Flow Information [Line Items]
Accrued capital expenditures		$ 518	$ 441	$ 524
Net realized and unrealized gain (loss) – nuclear decommissioning trust fund		167	(218)	163
Return on investment in industrial development revenue bonds		240	0	0
Stock Issued			31
Termination of a financing obligation		240	0	0
Issuance of common stock for stock-based compensation
Supplemental Cash Flow Information [Line Items]
Stock Issued		40	31	33
Issuance of common stock under the DRPlus
Supplemental Cash Flow Information [Line Items]
Stock Issued		7	8	0
Ameren Missouri
Supplemental Cash Flow Information [Line Items]
Accrued capital expenditures		270	243	301
Net realized and unrealized gain (loss) – nuclear decommissioning trust fund		167	(218)	163
Return on investment in industrial development revenue bonds		240	0	0
Termination of a financing obligation	$ 240	240	0	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		212	181	215
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