Schedule II - Valuation And Qualifying Accounts (Details) - Allowance For Doubtful Accounts - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 30	$ 31	$ 29
Charged to Costs and Expenses	39	51	34
Charged to Other Accounts	8	5	4
Deductions	47	57	36
Balance at End of Period	30	30	31
Ameren Missouri
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	12	13	13
Charged to Costs and Expenses	11	11	9
Charged to Other Accounts	0	0	0
Deductions	11	12	9
Balance at End of Period	12	12	13
Ameren Illinois
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	18	18	16
Charged to Costs and Expenses	28	40	25
Charged to Other Accounts	8	5	4
Deductions	36	45	27
Balance at End of Period	$ 18	$ 18	$ 18