Supplemental Information (Allowance for Doubtful Accounts) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance at January 1	$ 31	$ 29
Bad debt expense	51	34
Accounts Receivable, Credit Loss charged to other accounts	5	4
Net write-offs	(57)	(36)
Ending balance at December 31	$ 30	$ 31
Percentage of accounts receivable balances that are 30 days past due or are part of a deferred payment arrangement	22.00%	17.00%
Accounts receivable balances that are 30 days or more past due or part of a deferred payment arrangement	$ 114	$ 107
Ameren Missouri
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance at January 1	13	13
Bad debt expense	11	9
Accounts Receivable, Credit Loss charged to other accounts	0	0
Net write-offs	(12)	(9)
Ending balance at December 31	$ 12	$ 13
Percentage of accounts receivable balances that are 30 days past due or are part of a deferred payment arrangement	16.00%	14.00%
Accounts receivable balances that are 30 days or more past due or part of a deferred payment arrangement	$ 35	$ 35
Ameren Illinois
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance at January 1	18	16
Bad debt expense	40	25
Accounts Receivable, Credit Loss charged to other accounts	5	4
Net write-offs	(45)	(27)
Ending balance at December 31	$ 18	$ 18
Percentage of accounts receivable balances that are 30 days past due or are part of a deferred payment arrangement	27.00%	20.00%
Accounts receivable balances that are 30 days or more past due or part of a deferred payment arrangement	$ 79	$ 71