Fair Value Measurements (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Assets
Restricted cash equivalents	$ 27	$ 18
Derivative instruments	3	2
Consumers Energy Company
Assets
Restricted cash equivalents	27	17
Derivative instruments	3	2
Level 1
Assets
Cash equivalents	8	0
Restricted cash equivalents	27	18
Nonqualified deferred compensation plan assets	27	24
Liabilities
Nonqualified deferred compensation plan liabilities	27	24
Level 1 | Consumers Energy Company
Assets
Cash equivalents	0	0
Restricted cash equivalents	27	17
Nonqualified deferred compensation plan assets	20	18
Liabilities
Nonqualified deferred compensation plan liabilities	20	18
Fair Value, Inputs, Level 1, 2 and 3
Assets
Total assets	65	44
Liabilities
Total liabilities	27	24
Fair Value, Inputs, Level 1, 2 and 3 | Consumers Energy Company
Assets
Total assets	50	37
Liabilities
Total liabilities	$ 20	$ 18