Rate and Regulatory Matters (Narrative-Federal) (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	May 31, 2020	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities		$ 5,309	$ 5,848
ROE Change		0.50%
Revenues		$ 7,957	6,394	$ 5,794
Ameren Illinois Company
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities		2,313	2,374
Revenues		3,756	$ 2,895	$ 2,535
Midwest Independent Transmission System Operator, Inc
Public Utilities, General Disclosures [Line Items]
Revenues		19
Midwest Independent Transmission System Operator, Inc | Ameren Illinois Company
Public Utilities, General Disclosures [Line Items]
Revenues		13
Final Rate Order | Ameren Illinois Company
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities		$ 9
Final Rate Order | Midwest Independent Transmission System Operator, Inc
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Return on Equity, Percentage	10.02%