Fair Value Measurements (Summary of Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Assets
Restricted cash equivalents	$ 75	$ 21
Consumers Energy Company
Assets
Restricted cash equivalents	75	21
Fair Value, Inputs, Level 1, 2 and 3
Assets
Total assets	138	71
Liabilities
Total liabilities	34	30
Fair Value, Inputs, Level 1, 2 and 3 | Consumers Energy Company
Assets
Total assets	102	45
Liabilities
Total liabilities	25	22
Level 1
Assets
Cash equivalents	27	18
Restricted cash equivalents	75	21
Nonqualified deferred compensation plan assets	34	30
Liabilities
Nonqualified deferred compensation plan liabilities	34	30
Level 1 | Consumers Energy Company
Assets
Cash equivalents	0	0
Restricted cash equivalents	75	21
Nonqualified deferred compensation plan assets	25	22
Liabilities
Nonqualified deferred compensation plan liabilities	25	22
Fair Value, Inputs, Level 3
Assets
Derivative instruments	2	2
Fair Value, Inputs, Level 3 | Consumers Energy Company
Assets
Derivative instruments	$ 2	$ 2