Schedule II - Valuation And Qualifying Accounts (Details) - Allowance For Doubtful Accounts - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 31	$ 29	$ 50
Charged to Costs and Expenses	51	34	9
Charged to Other Accounts	5	4
Deductions	57	36	30
Balance at End of Period	30	31	29
Ameren Missouri
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	13	13	16
Charged to Costs and Expenses	11	9	5
Charged to Other Accounts	0	0	0
Deductions	12	9	8
Balance at End of Period	12	13	13
Ameren Illinois
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	18	16	34
Charged to Costs and Expenses	40	25	4
Charged to Other Accounts	5	4
Deductions	45	27	22
Balance at End of Period	$ 18	$ 18	$ 16