Retirement Benefits (Schedule Of Matching Contributions) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 43	$ 38	$ 38
Union Electric Company
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	23	21	20
Ameren Illinois Company
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	19	16	17
Other
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 1	$ 1	$ 1