Retirement Benefits (Schedule Of Matching Contributions) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 49	$ 43	$ 38
Ameren Missouri
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	27	23	21
Ameren Illinois
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	21	19	16
Other
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 1	$ 1	$ 1