Retirement Benefits (Schedule Of Matching Contributions) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 49	$ 49	$ 43
Ameren Missouri
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	26	27	23
Ameren Illinois
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	22	21	19
Other
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 1	$ 1	$ 1