Other Income, Net (Other Income And Expenses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Other Nonoperating Income (Expense) [Line Items]
Allowance for equity funds used during construction	$ 43	$ 32	$ 28
Interest income on industrial development revenue bonds	25	25	25
Other interest income	2	4	8
Non-service cost components of net periodic benefit income	136	116	90
Miscellaneous income	22	13	6
Donations	(9)	(25)	(12)
Miscellaneous expense	(17)	(14)	(15)
Total other income, net	202	151	130
Union Electric Company
Other Nonoperating Income (Expense) [Line Items]
Allowance for equity funds used during construction	26	19	19
Interest income on industrial development revenue bonds	25	25	25
Other interest income	1	1	1
Non-service cost components of net periodic benefit income	55	46	18
Miscellaneous income	3	4	5
Donations	(4)	(12)	(3)
Miscellaneous expense	(7)	(7)	(7)
Total other income, net	99	76	58
Defined Benefit Plan, Non-service Cost or Income Components - Tracker	(7)	(4)	29
Union Electric Company | Final Rate Order | Electric
Other Nonoperating Income (Expense) [Line Items]
Donations		(8)
Ameren Illinois Company
Other Nonoperating Income (Expense) [Line Items]
Allowance for equity funds used during construction	17	13	9
Other interest income	1	3	6
Non-service cost components of net periodic benefit income	55	48	47
Miscellaneous income	6	6	3
Donations	(5)	(5)	(5)
Miscellaneous expense	(8)	(6)	(7)
Total other income, net	$ 66	$ 59	$ 53