Fair Value Measurements (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Assets
Restricted cash equivalents	$ 28	$ 24
Derivative instruments	1	2
Liabilities
Derivative instruments	3	7
Consumers Energy Company
Assets
Restricted cash equivalents	26	22
Derivative instruments	1	2
Liabilities
Derivative instruments	0	0
Fair Value, Inputs, Level 1
Assets
Cash equivalents	40	0
Restricted cash equivalents	28	24
Nonqualified deferred compensation plan assets	26	27
Liabilities
Nonqualified deferred compensation plan liabilities	26	27
Fair Value, Inputs, Level 1 | Consumers Energy Company
Assets
Cash equivalents	0	0
Restricted cash equivalents	26	22
Nonqualified deferred compensation plan assets	20	21
Liabilities
Nonqualified deferred compensation plan liabilities	20	21
Fair Value, Inputs, Level 1, 2 and 3
Assets
Total assets	95	53
Liabilities
Total liabilities	29	34
Fair Value, Inputs, Level 1, 2 and 3 | Consumers Energy Company
Assets
Total assets	47	45
Liabilities
Total liabilities	$ 20	$ 21