v3.25.2
Supplemental Information (Allowance for Doubtful Accounts) (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Dec. 31, 2024
Allowance for Doubtful Accounts Receivable [Roll Forward]          
Beginning of period $ 41 $ 37 $ 30 $ 30  
Bad debt expense 3 6 19 16  
Charged to other accounts 2 1 3 4  
Net write-offs (7) (7) (13) (13)  
End of period 39 37 39 37  
Payables for purchased receivables 38   38   $ 43
Union Electric Company          
Allowance for Doubtful Accounts Receivable [Roll Forward]          
Beginning of period 12 11 12 12  
Bad debt expense 2 4 4 5  
Net write-offs (2) (3) (4) (5)  
End of period 12 12 12 12  
Ameren Illinois Company          
Allowance for Doubtful Accounts Receivable [Roll Forward]          
Beginning of period 29 26 18 18  
Bad debt expense 1 2 15 11  
Charged to other accounts 2 1 3 4  
Net write-offs (5) (4) (9) (8)  
End of period 27 $ 25 27 $ 25  
Payables for purchased receivables $ 38   $ 38   $ 43