Supplemental Information (Allowance for Doubtful Accounts) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance at January 1	$ 29	$ 50
Bad debt expense	38	9
Net write-offs	(36)	(30)
Ending balance at December 31	$ 31	$ 29
Percentage of accounts receivable balances that are 30 days past due or are part of a deferred payment arrangement	17.00%	20.00%
Accounts receivable balances that are 30 days or more past due or part of a deferred payment arrangement	$ 107	$ 94
Union Electric Company
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance at January 1	13	16
Bad debt expense	9	5
Net write-offs	(9)	(8)
Ending balance at December 31	$ 13	$ 13
Percentage of accounts receivable balances that are 30 days past due or are part of a deferred payment arrangement	14.00%	17.00%
Accounts receivable balances that are 30 days or more past due or part of a deferred payment arrangement	$ 35	$ 34
Ameren Illinois Company
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance at January 1	16	34
Bad debt expense	29	4
Net write-offs	(27)	(22)
Ending balance at December 31	$ 18	$ 16
Percentage of accounts receivable balances that are 30 days past due or are part of a deferred payment arrangement	20.00%	24.00%
Accounts receivable balances that are 30 days or more past due or part of a deferred payment arrangement	$ 71	$ 60