Other Income, Net (Other Income And Expenses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Other Nonoperating Income (Expense) [Line Items]
Allowance for equity funds used during construction	$ 54	$ 43	$ 43
Interest income on industrial development revenue bonds	1	24	25
Other interest income	32	11	2
Non-service cost components of net periodic benefit income	295	184	136
Miscellaneous income	7	10	10
Equity in earnings of subsidiaries	1	2	12
Donations	(24)	(26)	(9)
Miscellaneous expense	(18)	(22)	(17)
Total other income, net	348	226	202
Ameren Missouri
Other Nonoperating Income (Expense) [Line Items]
Allowance for equity funds used during construction	30	24	26
Interest income on industrial development revenue bonds	1	24	25
Other interest income	10	4	1
Non-service cost components of net periodic benefit income	97	55	55
Miscellaneous income	3	4	3
Donations	(2)	(3)	(4)
Miscellaneous expense	(9)	(9)	(7)
Total other income, net	130	99	99
Defined Benefit Plan, Non-service Cost or Income Components - Tracker	27	22	(7)
Ameren Missouri | Final Rate Order | Electric
Other Nonoperating Income (Expense) [Line Items]
Total other income, net	100
Ameren Illinois
Other Nonoperating Income (Expense) [Line Items]
Allowance for equity funds used during construction	19	18	17
Other interest income	21	7	1
Non-service cost components of net periodic benefit income	124	84	55
Miscellaneous income	4	5	6
Donations	(4)	(8)	(5)
Miscellaneous expense	(8)	(10)	(8)
Total other income, net	$ 156	$ 96	$ 66