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Supplemental Information (Allowance for Doubtful Accounts) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2023 | Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Beginning balance at January 1 | $ 31 | $ 29
Bad debt expense | 51 | 34
Accounts Receivable, Credit Loss charged to other accounts | 5 | 4
Net write-offs | (57) | (36)
Ending balance at December 31 | $ 30 | $ 31
Percentage of accounts receivable balances that are 30 days past due or are part of a deferred payment arrangement | 22.00% | 17.00%
Accounts receivable balances that are 30 days or more past due or part of a deferred payment arrangement | $ 114 | $ 107
Ameren Missouri |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Beginning balance at January 1 | 13 | 13
Bad debt expense | 11 | 9
Accounts Receivable, Credit Loss charged to other accounts | 0 | 0
Net write-offs | (12) | (9)
Ending balance at December 31 | $ 12 | $ 13
Percentage of accounts receivable balances that are 30 days past due or are part of a deferred payment arrangement | 16.00% | 14.00%
Accounts receivable balances that are 30 days or more past due or part of a deferred payment arrangement | $ 35 | $ 35
Ameren Illinois |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Beginning balance at January 1 | 18 | 16
Bad debt expense | 40 | 25
Accounts Receivable, Credit Loss charged to other accounts | 5 | 4
Net write-offs | (45) | (27)
Ending balance at December 31 | $ 18 | $ 18
Percentage of accounts receivable balances that are 30 days past due or are part of a deferred payment arrangement | 27.00% | 20.00%
Accounts receivable balances that are 30 days or more past due or part of a deferred payment arrangement | $ 79 | $ 71

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