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Supplemental Information (Allowance for Doubtful Accounts) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2024 | Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Beginning balance at January 1 | $ 30 | $ 31
Bad debt expense | 39 | 51
Accounts Receivable, Credit Loss charged to other accounts | 8 | 5
Net write-offs | (47) | (57)
Ending balance at December 31 | 30 | 30
Ameren Missouri |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Beginning balance at January 1 | 12 | 13
Bad debt expense | 11 | 11
Accounts Receivable, Credit Loss charged to other accounts | 0 | 0
Net write-offs | (11) | (12)
Ending balance at December 31 | 12 | 12
Ameren Illinois |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Beginning balance at January 1 | 18 | 18
Bad debt expense | 28 | 40
Accounts Receivable, Credit Loss charged to other accounts | 8 | 5
Net write-offs | (36) | (45)
Ending balance at December 31 | $ 18 | $ 18

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