Other Income, Net (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Other Nonoperating Income (Expense) [Line Items]
Allowance for equity funds used during construction	$ 11	$ 9	$ 19	$ 16
Interest income on industrial development revenue bonds	6	6	12	12
Non-service cost components of net periodic benefit income	47	34	93	68
Miscellaneous income	6	7	13	12
Donations	(2)	(1)	(4)	(4)
Miscellaneous expense	(6)	(6)	(11)	(9)
Total Other Income, Net	62	49	122	95
Union Electric Company
Other Nonoperating Income (Expense) [Line Items]
Allowance for equity funds used during construction	6	6	10	10
Interest income on industrial development revenue bonds	6	6	12	12
Non-service cost components of net periodic benefit income	14	14	28	28
Miscellaneous income	1	0	3	1
Donations	(1)	(1)	(2)	(1)
Miscellaneous expense	(2)	(1)	(4)	(3)
Total Other Income, Net	24	24	47	47
Defined Benefit Plan, Non-service Cost or Income Components - Tracker	5		11	(3)
Ameren Illinois Company
Other Nonoperating Income (Expense) [Line Items]
Allowance for equity funds used during construction	5	3	9	6
Non-service cost components of net periodic benefit income	21	14	42	28
Miscellaneous income	3	3	5	4
Donations	(1)	0	(2)	(3)
Miscellaneous expense	(3)	(4)	(5)	(5)
Total Other Income, Net	$ 25	$ 16	$ 49	$ 30