Rate And Regulatory Matters (Narrative-Federal) (Details) - USD ($) $ in Millions	1 Months Ended
	May 31, 2020	Mar. 31, 2022	Dec. 31, 2021
Rate And Regulatory Matters [Line Items]
Regulatory liabilities		$ 5,841	$ 5,848
Ameren Illinois Company
Rate And Regulatory Matters [Line Items]
Regulatory liabilities		2,442	$ 2,374
Final Rate Order | Ameren Illinois Company
Rate And Regulatory Matters [Line Items]
Regulatory liabilities		$ 9
Midwest Independent Transmission System Operator, Inc | Final Rate Order
Rate And Regulatory Matters [Line Items]
Approved return on equity percentage	10.02%