Other Income, Net (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Other Nonoperating Income (Expense) [Line Items]
Allowance for equity funds used during construction	$ 9	$ 9
Other interest income	8	8
Non-service cost components of net periodic benefit income	76	64
Miscellaneous income	2	2
Income (Loss) from Equity Method Investments	0	2
Donations	(2)	(2)
Miscellaneous expense	(4)	(5)
Total Other Income, Net	89	78
Union Electric Company
Other Nonoperating Income (Expense) [Line Items]
Allowance for equity funds used during construction	9	4
Other interest income	2	4
Non-service cost components of net periodic benefit income	35	14
Miscellaneous income	1	1
Donations	(1)	(1)
Miscellaneous expense	(2)	(3)
Total Other Income, Net	44	19
Defined Benefit Plan, Non-service Cost or Income Components - Tracker	(9)	17
Ameren Illinois Company
Other Nonoperating Income (Expense) [Line Items]
Allowance for equity funds used during construction	0	4
Other interest income	6	4
Non-service cost components of net periodic benefit income	27	31
Miscellaneous income	1	1
Donations	(1)	(1)
Miscellaneous expense	(2)	(2)
Total Other Income, Net	$ 31	$ 37