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Retirement Benefits (Cash Contributions Made To Benefit Plans) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020
Pension Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Cash contributions to benefit plans | $ 5 | $ 60 | $ 52
Postretirement Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Cash contributions to benefit plans | 2 | 2 | 2
Union Electric Company | Pension Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Cash contributions to benefit plans | 1 | 22 | 17
Union Electric Company | Postretirement Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Cash contributions to benefit plans | 1 | 1 | 1
Ameren Illinois Company | Pension Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Cash contributions to benefit plans | 3 | 28 | 27
Ameren Illinois Company | Postretirement Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Cash contributions to benefit plans | 1 | 1 | 1
Other | Pension Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Cash contributions to benefit plans | 1 | 10 | 8
Other | Postretirement Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Cash contributions to benefit plans | $ 0 | $ 0 | $ 0

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