v3.26.3
PRESENTATION OF FINANCIAL INFORMATION - Narrative (Details)
$ in Thousands
Sep. 30, 2026
USD ($)
member_system
non-utility_member
Dec. 31, 2025
USD ($)
Disaggregation of Revenue [Line Items]    
Regulatory liabilities $ 510,741 $ 358,446
Deferred Membership Withdrawal Income    
Disaggregation of Revenue [Line Items]    
Regulatory liabilities $ 99,104 $ 30,236
Class A Members    
Disaggregation of Revenue [Line Items]    
Number of electric distribution member systems | member_system 39  
Non-Utility Members    
Disaggregation of Revenue [Line Items]    
Number of members | non-utility_member 3