v3.25.2
Fair Value Measurements (Summary of Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($)
$ in Millions
Jun. 30, 2025
Dec. 31, 2024
Assets    
Restricted cash equivalents $ 81 $ 75
Consumers Energy Company    
Assets    
Restricted cash equivalents 81 75
Fair Value, Inputs, Level 1, 2 and 3    
Assets    
Total assets 206 138
Liabilities    
Total liabilities 38 34
Fair Value, Inputs, Level 1, 2 and 3 | Consumers Energy Company    
Assets    
Total assets 111 102
Liabilities    
Total liabilities 26 25
Fair Value, Inputs, Level 1    
Assets    
Cash equivalents 87 27
Restricted cash equivalents 81 75
Nonqualified deferred compensation plan assets 34 34
Liabilities    
Nonqualified deferred compensation plan liabilities 34 34
Fair Value, Inputs, Level 1 | Consumers Energy Company    
Assets    
Cash equivalents 0 0
Restricted cash equivalents 81 75
Nonqualified deferred compensation plan assets 26 25
Liabilities    
Nonqualified deferred compensation plan liabilities 26 25
Fair Value, Inputs, Level 2 And Level 3    
Assets    
Derivative instruments 4 2
Liabilities    
Derivative instruments 4 0
Fair Value, Inputs, Level 2 And Level 3 | Consumers Energy Company    
Assets    
Derivative instruments 4 2
Liabilities    
Derivative instruments $ 0 $ 0