Income Taxes (Schedule Of Components Of Income Tax Expense (Benefit)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Taxes [Line Items]
Current Federal taxes	$ 5	$ 7	$ 2
Current State taxes	1	(6)	5
Deferred Federal Income Tax Expense (Benefit)	194	170	187
Deferred State taxes	80	86	57
Amortization of excess deferred income taxes	(100)	(96)	(91)
Amortization of deferred investment tax credits	(4)	(4)	(5)
Income tax benefit	176	157	155
Union Electric Company
Income Taxes [Line Items]
Current Federal taxes	(26)	0	14
Current State taxes	(5)	0	3
Deferred Federal Income Tax Expense (Benefit)	93	65	82
Deferred State taxes	18	23	15
Amortization of excess deferred income taxes	(86)	(81)	(75)
Amortization of deferred investment tax credits	(4)	(4)	(5)
Income tax benefit	(10)	3	34
Ameren Illinois Company
Income Taxes [Line Items]
Current Federal taxes	46	(15)	12
Current State taxes	16	(7)	(6)
Deferred Federal Income Tax Expense (Benefit)	82	120	81
Deferred State taxes	48	59	52
Amortization of excess deferred income taxes	(13)	(14)	(15)
Amortization of deferred investment tax credits	0	0	0
Income tax benefit	179	143	124
Other
Income Taxes [Line Items]
Current Federal taxes	(15)	22	(24)
Current State taxes	(10)	1	8
Deferred Federal Income Tax Expense (Benefit)	19	(15)	24
Deferred State taxes	14	4	(10)
Amortization of excess deferred income taxes	(1)	(1)	(1)
Amortization of deferred investment tax credits	0	0	0
Income tax benefit	$ 7	$ 11	$ (3)