Fair Value Measurements (Summary of Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Assets
Restricted cash equivalents	$ 21	$ 18
Derivative instruments	2	2
Consumers Energy Company
Assets
Restricted cash equivalents	21	17
Derivative instruments	2	2
Fair Value, Inputs, Level 1
Assets
Cash equivalents	18	0
Restricted cash equivalents	21	18
Nonqualified deferred compensation plan assets	30	24
Liabilities
Nonqualified deferred compensation plan liabilities	30	24
Fair Value, Inputs, Level 1 | Consumers Energy Company
Assets
Cash equivalents	0	0
Restricted cash equivalents	21	17
Nonqualified deferred compensation plan assets	22	18
Liabilities
Nonqualified deferred compensation plan liabilities	22	18
Fair Value, Inputs, Level 1, 2 and 3
Assets
Total assets	71	44
Liabilities
Total liabilities	30	24
Fair Value, Inputs, Level 1, 2 and 3 | Consumers Energy Company
Assets
Total assets	45	37
Liabilities
Total liabilities	$ 22	$ 18