Income Taxes (Schedule Of Components Of Income Tax Expense (Benefit)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Taxes [Line Items]
Current Federal taxes	$ (47)	$ 5	$ 7
Current State taxes	1	1	(6)
Deferred Federal Income Tax Expense (Benefit)	260	194	170
Deferred State taxes	70	80	86
Amortization of excess deferred income taxes	(98)	(100)	(96)
Amortization of deferred investment tax credits	(3)	(4)	(4)
Income tax benefit	183	176	157
Ameren Missouri
Income Taxes [Line Items]
Current Federal taxes	(37)	(26)	0
Current State taxes	1	(5)	0
Deferred Federal Income Tax Expense (Benefit)	102	93	65
Deferred State taxes	9	18	23
Amortization of excess deferred income taxes	(80)	(86)	(81)
Amortization of deferred investment tax credits	(3)	(4)	(4)
Income tax benefit	(8)	(10)	3
Ameren Illinois
Income Taxes [Line Items]
Current Federal taxes	27	46	(15)
Current State taxes	5	16	(7)
Deferred Federal Income Tax Expense (Benefit)	123	82	120
Deferred State taxes	71	48	59
Amortization of excess deferred income taxes	(17)	(13)	(14)
Amortization of deferred investment tax credits	0	0	0
Income tax benefit	209	179	143
Other
Income Taxes [Line Items]
Current Federal taxes	(37)	(15)	22
Current State taxes	(5)	(10)	1
Deferred Federal Income Tax Expense (Benefit)	35	19	(15)
Deferred State taxes	(10)	14	4
Amortization of excess deferred income taxes	(1)	(1)	(1)
Amortization of deferred investment tax credits	0	0	0
Income tax benefit	$ (18)	$ 7	$ 11