Fair Value Measurements (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Assets
Restricted cash equivalents	$ 24	$ 17
Derivative instruments	2	1
Liabilities
Derivative instruments	7	11
Current assets held for sale	19	429
Consumers Energy Company
Assets
Restricted cash equivalents	22	15
Derivative instruments	2	1
Liabilities
Derivative instruments	0	0
Current assets held for sale	19	0
Level 1
Assets
Restricted cash equivalents	24	17
Nonqualified deferred compensation plan assets	27	23
Liabilities
Nonqualified deferred compensation plan liabilities	27	23
Level 1 | Consumers Energy Company
Assets
Restricted cash equivalents	22	15
Nonqualified deferred compensation plan assets	21	18
Liabilities
Nonqualified deferred compensation plan liabilities	21	18
Fair Value, Inputs, Level 1, 2 and 3
Assets
Total assets	53	41
Liabilities
Total liabilities	34	34
Fair Value, Inputs, Level 1, 2 and 3 | Consumers Energy Company
Assets
Total assets	45	34
Liabilities
Total liabilities	$ 21	$ 18