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Schedule II - Valuation And Qualifying Accounts (Details) - Allowance For Doubtful Accounts - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items] |  |  |
Balance at Beginning of Period | $ 31 | $ 29 | $ 50
Charged to Costs and Expenses | 51 | 34 | 9
Charged to Other Accounts | 5 | 4 |
Deductions | 57 | 36 | 30
Balance at End of Period | 30 | 31 | 29
Ameren Missouri |  |  |
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items] |  |  |
Balance at Beginning of Period | 13 | 13 | 16
Charged to Costs and Expenses | 11 | 9 | 5
Charged to Other Accounts | 0 | 0 | 0
Deductions | 12 | 9 | 8
Balance at End of Period | 12 | 13 | 13
Ameren Illinois |  |  |
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items] |  |  |
Balance at Beginning of Period | 18 | 16 | 34
Charged to Costs and Expenses | 40 | 25 | 4
Charged to Other Accounts | 5 | 4 |
Deductions | 45 | 27 | 22
Balance at End of Period | $ 18 | $ 18 | $ 16

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