Income Taxes (Schedule Of Deferred Tax Assets And Liabilities Resulting From Temporary Differences) (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Income Taxes [Line Items]
Plant-related	$ 4,940	$ 4,646
Regulatory assets and liabilities, net	(385)	(413)
Deferred employee benefit costs - asset	27
Deferred employee benefit costs - liability		26
Tax carryforwards	(503)	(218)
Other - liabilities	162	161
Total net accumulated deferred income tax liabilities (assets)	4,241	4,150
Accumulated deferred investment tax credits	233	26
Accumulated deferred income taxes and investment tax credits	4,474	4,176
Ameren Missouri
Income Taxes [Line Items]
Plant-related	2,429	2,370
Regulatory assets and liabilities, net	(193)	(206)
Deferred employee benefit costs - liability	25	48
Tax carryforwards	(355)	(124)
Other - liabilities	131	104
Total net accumulated deferred income tax liabilities (assets)	1,987	2,096
Accumulated deferred investment tax credits	230	26
Accumulated deferred income taxes and investment tax credits	2,217	2,122
Ameren Illinois
Income Taxes [Line Items]
Plant-related	2,250	2,030
Regulatory assets and liabilities, net	(170)	(184)
Deferred employee benefit costs - asset	77	55
Tax carryforwards	(45)	(33)
Other - liabilities	28	38
Total net accumulated deferred income tax liabilities (assets)	2,140	1,906
Accumulated deferred investment tax credits	3	0
Accumulated deferred income taxes and investment tax credits	2,143	1,906
Other
Income Taxes [Line Items]
Plant-related	261	246
Regulatory assets and liabilities, net	(22)	(23)
Deferred employee benefit costs - liability	25	33
Tax carryforwards	(103)	(61)
Other - liabilities	3	19
Total net accumulated deferred income tax liabilities (assets)	114	148
Accumulated deferred investment tax credits	0	0
Accumulated deferred income taxes and investment tax credits	$ 114	$ 148