Rate And Regulatory Matters (Narrative-Federal) (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	May 31, 2020	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Rate And Regulatory Matters [Line Items]
ROE Change				0.50%
Revenues		$ 1,760	$ 1,726	$ 3,822	$ 3,605
Ameren Illinois Company
Rate And Regulatory Matters [Line Items]
Revenues		$ 779	$ 769	1,880	$ 1,793
Midwest Independent Transmission System Operator, Inc
Rate And Regulatory Matters [Line Items]
Revenues				19
Midwest Independent Transmission System Operator, Inc | Ameren Illinois Company
Rate And Regulatory Matters [Line Items]
Revenues				$ 13
Midwest Independent Transmission System Operator, Inc | Final Rate Order
Rate And Regulatory Matters [Line Items]
Approved return on equity percentage	10.02%