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