v3.26.3
Derivative Instruments Gains (Loss) on Derivatives Recognized in Income (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Financial Swaps | Income Statement Location: us-gaap:RegulatedAndUnregulatedOperatingRevenue        
Derivative Instruments, Gain (Loss) [Line Items]        
Derivative, Gain (Loss) on Derivative, Net [1] $ 65 $ 270 $ 935 $ 559
Financial Swaps | Income Statement Location: us-gaap:UtilitiesOperatingExpenseFuelUsed        
Derivative Instruments, Gain (Loss) [Line Items]        
Derivative, Gain (Loss) on Derivative, Net [1] (6,233) (9,145) (33,823) (21,881)
Financial Swaps | Income Statement Location: us-gaap:UtilitiesOperatingExpensePurchasedPower        
Derivative Instruments, Gain (Loss) [Line Items]        
Derivative, Gain (Loss) on Derivative, Net [1] (417) (1,948) (3,972) (2,927)
Forward contracts | Income Statement Location: us-gaap:RegulatedAndUnregulatedOperatingRevenue        
Derivative Instruments, Gain (Loss) [Line Items]        
Derivative, Gain (Loss) on Derivative, Net [1] 0 (4) 58 387
Forward contracts | Income Statement Location: us-gaap:UtilitiesOperatingExpenseFuelUsed        
Derivative Instruments, Gain (Loss) [Line Items]        
Derivative, Gain (Loss) on Derivative, Net [1] (1,261) (322) (3,653) (1,153)
Forward contracts | Income Statement Location: us-gaap:UtilitiesOperatingExpensePurchasedPower        
Derivative Instruments, Gain (Loss) [Line Items]        
Derivative, Gain (Loss) on Derivative, Net [1] $ 0 $ 12 $ (58) $ (458)
[1] Excludes unrealized gains or losses on derivatives, which are recorded on the balance sheet as regulatory assets or regulatory liabilities.