v3.26.3
Derivative Instruments and Hedging Activities (Details)
MWh in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2026
USD ($)
MWh
Jun. 30, 2026
USD ($)
Mar. 31, 2026
USD ($)
Sep. 30, 2025
USD ($)
Jun. 30, 2025
USD ($)
Mar. 31, 2025
USD ($)
Sep. 30, 2026
USD ($)
MWh
Sep. 30, 2025
USD ($)
Dec. 31, 2025
USD ($)
Other Comprehensive Income (Loss), Net of Tax $ (434,000) $ (434,000) $ (434,000) $ (434,000) $ (434,000) $ (434,000) $ (1,302,000) $ (1,302,000)  
Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent (434,000)     (434,000)       (1,302,000)  
Regulatory assets 88,496,000           88,496,000   $ 82,136,000
Derivative [Line Items]                  
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, Tax 144,000     144,000     432,000 432,000  
Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent (434,000)     (434,000)       (1,302,000)  
Derivative Instruments, Gain (Loss) [Line Items]                  
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, before Tax, Parent (578,000)     (578,000)     (1,734,000) (1,734,000)  
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, Tax 144,000     144,000     432,000 432,000  
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax, Parent (434,000)     $ (434,000)     $ (1,302,000) $ (1,302,000)  
Expected Reclass Amount                  
Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent 1,700,000                
Derivative [Line Items]                  
Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent $ 1,700,000                
FTR [Member] | Not Designated as Hedging Instrument [Member]                  
Purchase of Units Derivative Instruments Financial Transmission Rights | MWh 6,723           6,723    
interest rate hedge | Not Designated as Hedging Instrument [Member]                  
Derivative Asset, Fair Value, Gross Asset $ 4,947,000           $ 4,947,000   1,584,000
Derivative [Line Items]                  
Derivative Asset, Fair Value, Gross Asset 4,947,000           4,947,000   1,584,000
Commodity Hedge | Not Designated as Hedging Instrument [Member]                  
Derivative Asset, Fair Value, Gross Asset $ 45,000           $ 45,000   0
Purchase of Units Derivative Instruments Financial Transmission Rights | MWh 12,031           12,031    
Derivative Liability, Fair Value, Gross Liability $ 2,743,000           $ 2,743,000    
Derivative [Line Items]                  
Derivative Asset, Fair Value, Gross Asset $ 45,000           $ 45,000   $ 0