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Retirement Benefits (Schedule Of Matching Contributions) (Details) - USD ($) $ in Millions | 12 Months Ended
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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

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