Retirement Benefits (Schedule Of SERP Trust Assets, ABO And Contributions) (Details) - DB SERP - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Trust assets	$ 0	$ 0	$ 0
Nonqualified Plan
Defined Benefit Plan Disclosure [Line Items]
ABO	118	149
Consumers Energy Company
Defined Benefit Plan Disclosure [Line Items]
Trust assets	0	0	$ 0
Consumers Energy Company | Nonqualified Plan
Defined Benefit Plan Disclosure [Line Items]
ABO	85	108
Trust assets | Nonqualified Plan
Defined Benefit Plan Disclosure [Line Items]
Trust assets	137	142
Trust assets | Consumers Energy Company | Nonqualified Plan
Defined Benefit Plan Disclosure [Line Items]
Trust assets	$ 101	$ 104