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Supplemental Information (Allowance for Doubtful Accounts) (Details) - USD ($) $ in Millions | 3 Months Ended |
--- | --- | ---
Mar. 31, 2024 | Mar. 31, 2023 | Dec. 31, 2023
Allowance for Doubtful Accounts Receivable [Roll Forward] |  |  |
Beginning of period | $ 30 | $ 31 |
Bad debt expense | 10 | 10 |
Charged to other accounts | 3 | 0 |
Net write-offs | (6) | (7) |
End of period | 37 | 34 |
Payables for purchased receivables | 43 |  | $ 42
Union Electric Company |  |  |
Allowance for Doubtful Accounts Receivable [Roll Forward] |  |  |
Beginning of period | 12 | 13 |
Bad debt expense | 1 | 2 |
Net write-offs | (2) | (3) |
End of period | 11 | 12 |
Ameren Illinois Company |  |  |
Allowance for Doubtful Accounts Receivable [Roll Forward] |  |  |
Beginning of period | 18 | 18 |
Bad debt expense | 9 | 8 |
Charged to other accounts | 3 | 0 |
Net write-offs | (4) | (4) |
End of period | 26 | $ 22 |
Payables for purchased receivables | $ 43 |  | $ 42

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