v3.26.1
Accounting for Derivative Instruments and Hedging Activities - Derivative Assets and Liabilities (Details)
$ in Thousands, MMBTU in Millions
Jun. 30, 2026
USD ($)
MMBTU
Dec. 31, 2025
USD ($)
MMBTU
Derivative [Line Items]    
Current, Assets $ 38,293 $ 37,448
Long-term, Assets 5,188 11,261
Current, Liabilities 305,722 359,890
Long-term, Liabilities 223,375 213,531
Electric derivative instruments    
Derivative [Line Items]    
Assets 37,801 41,974
Derivative Liability 465,515 493,334
Natural gas derivative instruments    
Derivative [Line Items]    
Assets 5,680 6,735
Derivative Liability 63,582 80,087
Not Designated as Hedging Instrument    
Derivative [Line Items]    
Current, Assets 38,293 37,448
Long-term, Assets 5,188 11,261
Assets 43,481 48,709
Current, Liabilities 305,722 359,890
Long-term, Liabilities 223,375 213,531
Derivative Liability 529,097 573,421
Not Designated as Hedging Instrument | Electric derivative instruments    
Derivative [Line Items]    
Assets 37,801 41,974
Derivative Liability $ 465,515 $ 493,334
Not Designated as Hedging Instrument | Natural gas derivatives (MMBtus)3    
Derivative [Line Items]    
Derivative, Nonmonetary Notional Amount | MMBTU 231.0 289.0
Not Designated as Hedging Instrument | Natural gas derivative instruments    
Derivative [Line Items]    
Assets $ 5,680 $ 6,735
Derivative Liability $ 63,582 $ 80,087
Not Designated as Hedging Instrument | Electric Generation Fuel    
Derivative [Line Items]    
Derivative, Nonmonetary Notional Amount | MMBTU 237.9 252.9
Not Designated as Hedging Instrument | Purchased Electricity    
Derivative [Line Items]    
Derivative, Nonmonetary Notional Amount | MMBTU 27.2 33.8