v3.26.1
Fair Value Measurements - Level 3 Rollforward (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Balance at beginning of period $ (224,852) $ (202,133) $ (205,953) $ (173,719)
Included in regulatory assets / liabilities (9,376) 106,311 (62,464) 48,443
Settlements 20,908 6,996 55,097 36,450
Balance at end of period (213,320) (88,826) (213,320) (88,826)
Electric derivative instruments        
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Balance at beginning of period (227,299) (203,718) (209,283) (175,110)
Included in regulatory assets / liabilities (9,684) 102,904 (63,389) 44,419
Settlements 21,955 7,450 57,644 37,327
Balance at end of period (215,028) (93,364) (215,028) (93,364)
Natural gas derivative instruments        
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Balance at beginning of period 2,447 1,585 3,330 1,391
Included in regulatory assets / liabilities 308 3,407 925 4,024
Settlements (1,047) (454) (2,547) (877)
Balance at end of period $ 1,708 $ 4,538 $ 1,708 $ 4,538