Rate and Regulatory Matters (Narrative-Federal) (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	May 31, 2020	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Public Utilities, General Disclosures [Line Items]
Capital expenditures			$ 3,597	$ 3,351	$ 3,479
ROE Change			0.50%
Revenues			$ 7,500	7,957	6,394
Forecast
Public Utilities, General Disclosures [Line Items]
Capital expenditures		$ 1,800
Ameren Illinois
Public Utilities, General Disclosures [Line Items]
Capital expenditures			1,731	1,601	1,432
Revenues			3,482	$ 3,756	$ 2,895
Midwest Independent Transmission System Operator, Inc
Public Utilities, General Disclosures [Line Items]
Revenues			21
Midwest Independent Transmission System Operator, Inc | Ameren Illinois
Public Utilities, General Disclosures [Line Items]
Revenues			$ 15
Final Rate Order | Midwest Independent Transmission System Operator, Inc
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Return on Equity, Percentage	10.02%