v3.26.3
Fair Value Measurements (Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($)
$ in Millions
Sep. 30, 2026
Dec. 31, 2025
Assets    
Restricted cash equivalents $ 102 $ 106
Consumers Energy Company    
Assets    
Restricted cash equivalents 68 86
Fair Value, Inputs, Level 1, 2 and 3    
Assets    
Total assets 241 298
Liabilities    
Total liabilities 37 39
Fair Value, Inputs, Level 1, 2 and 3 | Consumers Energy Company    
Assets    
Total assets 99 115
Liabilities    
Total liabilities 29 27
Fair Value, Inputs, Level 1    
Assets    
Cash equivalents 88 154
Restricted cash equivalents 102 106
Nonqualified deferred compensation plan assets 37 36
Liabilities    
Nonqualified deferred compensation plan liabilities 37 36
Fair Value, Inputs, Level 1 | Consumers Energy Company    
Assets    
Cash equivalents 0 0
Restricted cash equivalents 68 86
Nonqualified deferred compensation plan assets 29 27
Liabilities    
Nonqualified deferred compensation plan liabilities 29 27
Fair Value, Inputs, Level 2 And Level 3    
Assets    
Derivative instruments 14 2
Liabilities    
Derivative instruments 0 3
Fair Value, Inputs, Level 2 And Level 3 | Consumers Energy Company    
Assets    
Derivative instruments 2 2
Liabilities    
Derivative instruments $ 0 $ 0