v3.26.1
Regulatory Assets and Liabilities (Details) - USD ($)
$ in Thousands
Mar. 31, 2026
Dec. 31, 2025
Regulatory Liability [Line Items]    
Regulatory assets $ 303,826 $ 311,373
Regulatory liabilities (331,776) (336,305)
Net regulatory liabilities (27,950) (24,932)
Deferred revenue    
Regulatory Liability [Line Items]    
Regulatory liabilities (272,000) (272,000)
Unrealized gain on equity investments    
Regulatory Liability [Line Items]    
Regulatory liabilities (16,436) (18,489)
Post-retirement medical gain    
Regulatory Liability [Line Items]    
Regulatory liabilities (21,044) (21,044)
Other    
Regulatory Liability [Line Items]    
Regulatory liabilities (22,296) (24,772)
Deferred income taxes    
Regulatory Liability [Line Items]    
Regulatory assets 164,726 160,754
Refinancing fees    
Regulatory Liability [Line Items]    
Regulatory assets $ 78,579 80,122
Remaining Recovery Period 24 years  
Unrealized loss on interest rate swaps    
Regulatory Liability [Line Items]    
Regulatory assets $ 20,263 21,066
Remaining Recovery Period 6 years  
Unrealized loss on commodity derivatives    
Regulatory Liability [Line Items]    
Regulatory assets $ 19,190 28,239
Remaining Recovery Period 8 years  
Other    
Regulatory Liability [Line Items]    
Regulatory assets $ 21,068 $ 21,192
Remaining Recovery Period 49 years