v3.26.3
Contingencies and Commitments (Narrative) (Details)
$ in Millions
 1 Months Ended 9 Months Ended 12 Months Ended
Oct. 27, 2026
USD ($)
Dec. 31, 2025
USD ($)
Sep. 30, 2026
USD ($)
facility
Dec. 31, 2022
USD ($)
Loss Contingencies [Line Items]        
Environmental Loss Contingency, Statement Of Financial Position, Extensible Enumeration, Not Disclosed Flag     recorded liability  
Regulatory assets   $ 3,355 $ 3,381  
Consumers Energy Company        
Loss Contingencies [Line Items]        
Regulatory assets   3,355 3,381  
Consumers Energy Company | MGP sites        
Loss Contingencies [Line Items]        
Regulatory assets     113  
Consumers Energy Company | Ludington Plant Overhaul Contract Dispute        
Loss Contingencies [Line Items]        
Damages sought       $ 15
Damages awarded   383    
Additional damages awarded   $ 11    
Estimate of shared costs     350  
Consumers Energy Company | Ludington Plant Overhaul Contract Dispute | Subsequent Event        
Loss Contingencies [Line Items]        
Damages sought $ 485      
Loss contingency accrual prejudgment interest $ 90      
Bay Harbor        
Loss Contingencies [Line Items]        
Accrual for environmental loss contingencies     $ 47  
Discount rate (in percent)     4.34%  
Accrual for environmental loss contingencies, inflation rate (in percent)     1.00%  
Accrual for environmental loss contingencies, gross     $ 59  
NREPA | Electric Utility | Consumers Energy Company        
Loss Contingencies [Line Items]        
Accrual for environmental loss contingencies     2  
NREPA | Maximum | Electric Utility | Consumers Energy Company        
Loss Contingencies [Line Items]        
Remediation and other response activity costs     3  
CERCLA Liability | Consumers Energy Company        
Loss Contingencies [Line Items]        
Accrual for environmental loss contingencies     21  
CERCLA Liability | Minimum | Consumers Energy Company        
Loss Contingencies [Line Items]        
Remediation and other response activity costs     21  
CERCLA Liability | Maximum | Consumers Energy Company        
Loss Contingencies [Line Items]        
Remediation and other response activity costs     57  
MGP sites | Consumers Energy Company        
Loss Contingencies [Line Items]        
Accrual for environmental loss contingencies     $ 95  
Number of former MGPs | facility     23  
Regulatory asset collection period (in years)     10 years