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v3.25.1

Related Party Transactions (Effects of Related-party Transactions on the Statement of Income) (Details) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2025 | Mar. 31, 2024
Related Party Transaction [Line Items] |  |
Operating Revenues | $ 2,097 | $ 1,816
Other operations and maintenance | 485 | 470
Interest Charges | 175 | 154
Union Electric Company |  |
Related Party Transaction [Line Items] |  |
Operating Revenues | 957 | 775
Other operations and maintenance | 250 | 254
Interest Charges | 60 | 62
Union Electric Company | Ameren Missouri Power Supply Agreements with Ameren Illinois | Related Party |  |
Related Party Transaction [Line Items] |  |
Operating Revenues |  | 1
Union Electric Company | Ameren Missouri and Ameren Illinois Rent and Facility Services | Related Party |  |
Related Party Transaction [Line Items] |  |
Operating Revenues | 7 | 7
Other operations and maintenance | 1 | 1
Union Electric Company | Ameren Missouri and Ameren Illinois Miscellaneous Support Services | Related Party |  |
Related Party Transaction [Line Items] |  |
Operating Revenues | 1 | 1
Union Electric Company | Total Related Party Operating Revenues | Related Party |  |
Related Party Transaction [Line Items] |  |
Operating Revenues | 7 | 7
Union Electric Company | Ameren Missouri and Ameren Illinois Transmission Services from ATXI | Related Party |  |
Related Party Transaction [Line Items] |  |
Purchased Power | 3 | 2
Union Electric Company | Purchased Power | Related Party |  |
Related Party Transaction [Line Items] |  |
Purchased Power | 3 | 2
Union Electric Company | Ameren Services Support Services Agreement | Related Party |  |
Related Party Transaction [Line Items] |  |
Other operations and maintenance | 44 | 38
Union Electric Company | Total Related Party Other Operations and Maintenance | Related Party |  |
Related Party Transaction [Line Items] |  |
Other operations and maintenance | 44 | 38
Union Electric Company | Money pool interest | Related Party |  |
Related Party Transaction [Line Items] |  |
Interest Charges | 1 | 3
Union Electric Company | Long-Term Debt | Related Party |  |
Related Party Transaction [Line Items] |  |
Interest Charges | 1 | 0
Ameren Illinois Company |  |
Related Party Transaction [Line Items] |  |
Operating Revenues | 1,100 | 1,000
Purchased Power | 175 | 164
Other operations and maintenance | 236 | 210
Interest Charges | 62 | 55
Ameren Illinois Company | Ameren Missouri and Ameren Illinois Rent and Facility Services | Related Party |  |
Related Party Transaction [Line Items] |  |
Operating Revenues | 1 | 1
Other operations and maintenance | 1 | 1
Ameren Illinois Company | Ameren Missouri and Ameren Illinois Miscellaneous Support Services | Related Party |  |
Related Party Transaction [Line Items] |  |
Operating Revenues | 2 | 1
Ameren Illinois Company | Total Related Party Operating Revenues | Related Party |  |
Related Party Transaction [Line Items] |  |
Operating Revenues | 2 | 1
Ameren Illinois Company | Ameren Illinois Power Supply Agreements with Ameren Missouri | Related Party |  |
Related Party Transaction [Line Items] |  |
Purchased Power |  | 1
Ameren Illinois Company | Ameren Missouri and Ameren Illinois Transmission Services from ATXI | Related Party |  |
Related Party Transaction [Line Items] |  |
Purchased Power | 1 | 1
Ameren Illinois Company | Purchased Power | Related Party |  |
Related Party Transaction [Line Items] |  |
Purchased Power | 1 | 1
Ameren Illinois Company | Ameren Services Support Services Agreement | Related Party |  |
Related Party Transaction [Line Items] |  |
Other operations and maintenance | 40 | 37
Ameren Illinois Company | Total Related Party Other Operations and Maintenance | Related Party |  |
Related Party Transaction [Line Items] |  |
Other operations and maintenance | 41 | 37
Ameren Illinois Company | Money pool interest | Related Party |  |
Related Party Transaction [Line Items] |  |
Interest Charges | 1 | 2
Ameren Illinois Company | Long-Term Debt | Related Party |  |
Related Party Transaction [Line Items] |  |
Interest Charges | $ 1 | $ 0

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