Fair Value Measurements (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Assets
Restricted cash equivalents	$ 27	$ 18
Derivative instruments	1	2
Consumers Energy Company
Assets
Restricted cash equivalents	26	17
Derivative instruments	1	2
Level 1
Assets
Cash equivalents	216	0
Restricted cash equivalents	27	18
Nonqualified deferred compensation plan assets	26	24
Liabilities
Nonqualified deferred compensation plan liabilities	26	24
Level 1 | Consumers Energy Company
Assets
Cash equivalents	166	0
Restricted cash equivalents	26	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	270	44
Liabilities
Total liabilities	26	24
Fair Value, Inputs, Level 1, 2 and 3 | Consumers Energy Company
Assets
Total assets	213	37
Liabilities
Total liabilities	$ 20	$ 18