v3.26.1
Fair Value Measurements - Assets and Liabilities (Details) - USD ($)
$ in Thousands
Jun. 30, 2026
Dec. 31, 2025
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets $ 43,481 $ 48,709
Compliance obligation 73,822 96,490
Total liabilities 602,919 669,911
Electric derivative instruments    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Assets 37,801 41,974
Derivative Liability 465,515 493,334
Natural gas derivative instruments    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Assets 5,680 6,735
Derivative Liability 63,582 80,087
Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets 37,041 41,192
Compliance obligation 73,822 96,490
Total liabilities 383,159 456,442
Level 2 | Electric derivative instruments    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Assets 34,190 38,930
Derivative Liability 246,876 281,007
Level 2 | Natural gas derivative instruments    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Assets 2,851 2,262
Derivative Liability 62,461 78,945
Level 3    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets 6,440 7,517
Compliance obligation 0 0
Total liabilities 219,760 213,469
Level 3 | Electric derivative instruments    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Assets 3,611 3,044
Derivative Liability 218,639 212,327
Level 3 | Natural gas derivative instruments    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Assets 2,829 4,473
Derivative Liability $ 1,121 $ 1,142