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Schedule II - Valuation And Qualifying Accounts (Details) - Allowance For Doubtful Accounts - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items] |  |  |
Balance at Beginning of Period | $ 30 | $ 31 | $ 29
Charged to Costs and Expenses | 39 | 51 | 34
Charged to Other Accounts | 8 | 5 | 4
Deductions | 47 | 57 | 36
Balance at End of Period | 30 | 30 | 31
Ameren Missouri |  |  |
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items] |  |  |
Balance at Beginning of Period | 12 | 13 | 13
Charged to Costs and Expenses | 11 | 11 | 9
Charged to Other Accounts | 0 | 0 | 0
Deductions | 11 | 12 | 9
Balance at End of Period | 12 | 12 | 13
Ameren Illinois |  |  |
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items] |  |  |
Balance at Beginning of Period | 18 | 18 | 16
Charged to Costs and Expenses | 28 | 40 | 25
Charged to Other Accounts | 8 | 5 | 4
Deductions | 36 | 45 | 27
Balance at End of Period | $ 18 | $ 18 | $ 18

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