v3.26.1
Related Party Transactions (Schedule of Affiliate Receivables and Payables) (Details) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Related Party Transaction [Line Items]    
Accounts Payable, Related Parties, Current $ 998 $ 1,254
Accounts Receivable, Related Parties, Current 600 665
Union Electric Company | Related Party    
Related Party Transaction [Line Items]    
Accounts Payable, Related Parties, Current 93 61
Accounts Receivable, Related Parties, Current 15 15
Union Electric Company | Income taxes payable to parent | Related Party    
Related Party Transaction [Line Items]    
Accounts Payable, Related Parties, Current 38 0
Union Electric Company | Income taxes receivable from parent | Related Party    
Related Party Transaction [Line Items]    
Accounts Receivable, Related Parties, Current 0 3
Ameren Illinois Company | Related Party    
Related Party Transaction [Line Items]    
Accounts Payable, Related Parties, Current 63 57
Accounts Receivable, Related Parties, Current 15 18
Ameren Illinois Company | Income taxes payable to parent | Related Party    
Related Party Transaction [Line Items]    
Accounts Payable, Related Parties, Current 10 4
Ameren Illinois Company | Income taxes receivable from parent | Related Party    
Related Party Transaction [Line Items]    
Accounts Receivable, Related Parties, Current $ 0 $ 7