Income Taxes (Schedule Of Deferred Tax Assets And Liabilities Resulting From Temporary Differences) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Income Taxes [Line Items]
Plant-related	$ 4,416	$ 4,129
Regulatory assets and liabilities, net	(449)	(483)
Deferred employee benefit costs - asset	(70)	(88)
Tax carryforwards	(228)	(198)
Other - liabilities	110	109
Total net accumulated deferred income tax liabilities (assets)	3,779	3,469
Accumulated deferred investment tax credits	25	30
Accumulated deferred income taxes and investment tax credits	3,804	3,499
Union Electric Company
Income Taxes [Line Items]
Plant-related	2,297	2,188
Regulatory assets and liabilities, net	(233)	(259)
Deferred employee benefit costs - asset	(55)	(52)
Tax carryforwards	(122)	(68)
Other - liabilities	70	13
Total net accumulated deferred income tax liabilities (assets)	1,957	1,822
Accumulated deferred investment tax credits	25	30
Accumulated deferred income taxes and investment tax credits	1,982	1,852
Ameren Illinois Company
Income Taxes [Line Items]
Plant-related	1,880	1,715
Regulatory assets and liabilities, net	(193)	(199)
Deferred employee benefit costs - liability	28	17
Tax carryforwards	(34)	(46)
Other - liabilities	18	71
Total net accumulated deferred income tax liabilities (assets)	1,699	1,558
Accumulated deferred investment tax credits	0	0
Accumulated deferred income taxes and investment tax credits	1,699	1,558
Other
Income Taxes [Line Items]
Plant-related	239	226
Regulatory assets and liabilities, net	(23)	(25)
Deferred employee benefit costs - asset	(43)	(53)
Tax carryforwards	(72)	(84)
Other - liabilities	22	25
Total net accumulated deferred income tax liabilities (assets)	123	89
Accumulated deferred investment tax credits	0	0
Accumulated deferred income taxes and investment tax credits	$ 123	$ 89