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Related Party Transactions (Narrative) (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2024 | Dec. 31, 2023
Related Party Transaction [Line Items] |  |
Interconnection agreement, optional termination period | 3 years |
Other assets | $ 1,123 | $ 921
Ameren Illinois |  |
Related Party Transaction [Line Items] |  |
Other assets | 697 | 603
Ameren Missouri |  |
Related Party Transaction [Line Items] |  |
Other assets | 254 | 152
Ameren Illinois Capacity Supply Agreements with Ameren Missouri | Ameren Illinois | 2021 Procurements |  |
Related Party Transaction [Line Items] |  |
Energy supply agreements amount | $ 2 |
Ameren Services Support Services Agreement |  |
Related Party Transaction [Line Items] |  |
Support services agreement, optional termination period | 60 days |
Ameren Services Support Services Agreement | Ameren Illinois |  |
Related Party Transaction [Line Items] |  |
Other assets | $ 32 | 34
Ameren Services Support Services Agreement | Ameren Missouri |  |
Related Party Transaction [Line Items] |  |
Other assets | $ 29 | $ 31

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