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Related Party Transactions (Narrative) (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2023 | Dec. 31, 2022
Related Party Transaction [Line Items] |  |
Interconnection agreement, optional termination period | 3 years |
Other assets | $ 921 | $ 768
Ameren Illinois |  |
Related Party Transaction [Line Items] |  |
Other assets | 603 | 482
Ameren Missouri |  |
Related Party Transaction [Line Items] |  |
Other assets | 152 | 140
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 | $ 34 | 43
Ameren Services Support Services Agreement | Ameren Missouri |  |
Related Party Transaction [Line Items] |  |
Other assets | $ 31 | $ 41

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