Retirement Benefits (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023 USD ($) bond	Dec. 31, 2022 USD ($)	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Funded (Unfunded) Status of Plan		$ 551	$ 377
Defined Benefit Plan Assumptions Used Calculating Benefit Obligation, Change in Discount Rate		0.30%
Number of high-quality corporate bonds | bond		860
Defined benefit plan estimated future employer contributions over next five years		$ 120
Collateralized loan percentage compared to asset's market value		103.00%
Securities Loaned		$ 234	239
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Funded (Unfunded) Status of Plan		$ 14	$ (34)
Expected return on plan assets		6.75%	6.50%	6.50%
Pension Benefits | Forecast
Defined Benefit Plan Disclosure [Line Items]
Expected return on plan assets	6.75%
Ameren Missouri | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Future funding requirement, percentage		40.00%
Ameren Illinois | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Future funding requirement, percentage		50.00%