Income Taxes (Schedule Of Deferred Tax Assets And Liabilities Resulting From Temporary Differences) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Income Taxes [Line Items]
Plant-related	$ 4,646	$ 4,416
Regulatory assets and liabilities, net	(413)	(449)
Deferred employee benefit costs - asset	(26)	(70)
Tax carryforwards	(218)	(228)
Other - liabilities	161	110
Total net accumulated deferred income tax liabilities (assets)	4,150	3,779
Accumulated deferred investment tax credits	26	25
Accumulated deferred income taxes and investment tax credits	4,176	3,804
Ameren Missouri
Income Taxes [Line Items]
Plant-related	2,370	2,297
Regulatory assets and liabilities, net	(206)	(233)
Deferred employee benefit costs - asset	(48)	(55)
Tax carryforwards	(124)	(122)
Other - liabilities	104	70
Total net accumulated deferred income tax liabilities (assets)	2,096	1,957
Accumulated deferred investment tax credits	26	25
Accumulated deferred income taxes and investment tax credits	2,122	1,982
Ameren Illinois
Income Taxes [Line Items]
Plant-related	2,030	1,880
Regulatory assets and liabilities, net	(184)	(193)
Deferred employee benefit costs - liability	55	28
Tax carryforwards	(33)	(34)
Other - liabilities	38	18
Total net accumulated deferred income tax liabilities (assets)	1,906	1,699
Accumulated deferred investment tax credits	0	0
Accumulated deferred income taxes and investment tax credits	1,906	1,699
Other
Income Taxes [Line Items]
Plant-related	246	239
Regulatory assets and liabilities, net	(23)	(23)
Deferred employee benefit costs - asset	(33)	(43)
Tax carryforwards	(61)	(72)
Other - liabilities	19	22
Total net accumulated deferred income tax liabilities (assets)	148	123
Accumulated deferred investment tax credits	0	0
Accumulated deferred income taxes and investment tax credits	$ 148	$ 123