Fair Value Measurements (Summary of Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Assets
Restricted cash equivalents	$ 90	$ 21
Derivative instruments	5	2
Consumers Energy Company
Assets
Restricted cash equivalents	89	21
Derivative instruments	5	2
Fair Value, Inputs, Level 1
Assets
Cash equivalents	167	18
Restricted cash equivalents	90	21
Nonqualified deferred compensation plan assets	32	30
Liabilities
Nonqualified deferred compensation plan liabilities	32	30
Fair Value, Inputs, Level 1 | Consumers Energy Company
Assets
Cash equivalents	154	0
Restricted cash equivalents	89	21
Nonqualified deferred compensation plan assets	23	22
Liabilities
Nonqualified deferred compensation plan liabilities	23	22
Fair Value, Inputs, Level 1, 2 and 3
Assets
Total assets	294	71
Liabilities
Total liabilities	32	30
Fair Value, Inputs, Level 1, 2 and 3 | Consumers Energy Company
Assets
Total assets	271	45
Liabilities
Total liabilities	$ 23	$ 22