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Schedule II - Valuation And Qualifying Accounts (Details) - Allowance For Doubtful Accounts - USD ($)
$ in Millions
12 Months Ended
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