Income Taxes (Schedule Of Net Operating Loss Carryforwards And Tax Credit Carryforwards) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Net operating loss carryforwards:
Net operating loss carryforwards:	$ 47	$ 65
Tax credit carryforwards:	181	133
Federal
Net operating loss carryforwards:
Net operating loss carryforwards:	11	34
Tax credit carryforwards:	176	126
State
Net operating loss carryforwards:
Net operating loss carryforwards:	36	31
Tax credit carryforwards:	5	7
Union Electric Company
Net operating loss carryforwards:
Net operating loss carryforwards:	4	3
Tax credit carryforwards:	118	65
Union Electric Company | Federal
Net operating loss carryforwards:
Net operating loss carryforwards:	3	2
Tax credit carryforwards:	118	65
Union Electric Company | State
Net operating loss carryforwards:
Net operating loss carryforwards:	1	1
Tax credit carryforwards:	0	0
Ameren Illinois Company
Net operating loss carryforwards:
Net operating loss carryforwards:	30	42
Tax credit carryforwards:	4	4
Ameren Illinois Company | Federal
Net operating loss carryforwards:
Net operating loss carryforwards:	4	17
Tax credit carryforwards:	3	3
Ameren Illinois Company | State
Net operating loss carryforwards:
Net operating loss carryforwards:	26	25
Tax credit carryforwards:	1	1
Other
Net operating loss carryforwards:
Net operating loss carryforwards:	13	20
Tax credit carryforwards:	59	64
Other | Federal
Net operating loss carryforwards:
Net operating loss carryforwards:	4	15
Tax credit carryforwards:	55	58
Other | State
Net operating loss carryforwards:
Net operating loss carryforwards:	9	5
Tax credit carryforwards:	$ 4	$ 6