Other Income, Net (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Other Nonoperating Income (Expense) [Line Items]
Allowance for equity funds used during construction	$ 16	$ 9
Other interest income	11	8
Non-service cost components of net periodic benefit income	66	76
Miscellaneous income	3	2
Income (Loss) from Equity Method Investments	(4)	0
Donations	(2)	(2)
Miscellaneous expense	(5)	(4)
Total Other Income, Net	85	89
Union Electric Company
Other Nonoperating Income (Expense) [Line Items]
Allowance for equity funds used during construction	8	9
Other interest income	2	2
Non-service cost components of net periodic benefit income	35	35
Miscellaneous income	1	1
Donations	(1)	(1)
Miscellaneous expense	(2)	(2)
Total Other Income, Net	43	44
Defined Benefit Plan, Non-service Cost or Income Components - Tracker	(16)	(9)
Ameren Illinois Company
Other Nonoperating Income (Expense) [Line Items]
Allowance for equity funds used during construction	7	0
Other interest income	9	6
Non-service cost components of net periodic benefit income	20	27
Miscellaneous income	2	1
Donations	(1)	(1)
Miscellaneous expense	(3)	(2)
Total Other Income, Net	$ 34	$ 31