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v3.25.4

Related Party Transactions (Narrative) (Details) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2025 USD ($) MWh $ / MWh | Dec. 31, 2024 USD ($)
Related Party Transaction [Line Items] |  |
Interconnection agreement, optional termination period | 3 years |
Other assets | $ 1,154 | $ 1,123
Ameren Illinois |  |
Related Party Transaction [Line Items] |  |
Other assets | 789 | 697
Ameren Missouri |  |
Related Party Transaction [Line Items] |  |
Other assets | 244 | 254
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 | $ 38 | 32
Ameren Services Support Services Agreement | Ameren Missouri |  |
Related Party Transaction [Line Items] |  |
Other assets | $ 36 | $ 29
Ameren Illinois Power Supply Agreements with Ameren Missouri | Ameren Illinois | September 2021 Procurement [Member] |  |
Related Party Transaction [Line Items] |  |
Related Party Long Term Contract For Purchase Of Electric Power | MWh | 136,000 |
Related Party Long Term Contract For Purchase Of Electric Power Rate | $ / MWh | 37 |

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