v3.26.1
Fair Value Measurements - Valuation Techniques for Measurement with Unobservable Inputs (Details)
$ in Thousands
 6 Months Ended 12 Months Ended
Jun. 30, 2026
USD ($)
$ / MWh
$ / MMBTU
Dec. 31, 2025
USD ($)
$ / MWh
$ / MMBTU
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Fair Value measurement, sensitivity analysis, hypothetical increase or decrease of market prices, result on fair value 10.00% 10.00%
Fair Value Measurements, Sensitivity Analysis, Hypothetical Increase or Decrease of Market Prices, Result on Fair Value $ 50,700 $ 48,100
Electric derivative instruments    
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Derivative Assets 37,801 41,974
Derivative Liability $ 465,515 $ 493,334
Electric derivative instruments | Low | Discounted cash flow    
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Price (per MWh) | $ / MWh 19.16 18.40
Electric derivative instruments | High | Discounted cash flow    
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Price (per MWh) | $ / MWh 115.77 126.87
Electric derivative instruments | Weighted Average | Discounted cash flow    
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Price (per MWh) | $ / MWh 54.94 57.64
Electric derivative instruments | Level 3    
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Derivative Assets $ 3,611 $ 3,044
Derivative Liability 218,639 212,327
Natural gas derivative instruments    
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Derivative Assets 5,680 6,735
Derivative Liability $ 63,582 $ 80,087
Natural gas derivative instruments | Low | Discounted cash flow    
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Fair Value Inputs, Price Per Millions of BTU | $ / MMBTU 0.95 1.53
Natural gas derivative instruments | High | Discounted cash flow    
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Fair Value Inputs, Price Per Millions of BTU | $ / MMBTU 4.27 4.46
Natural gas derivative instruments | Weighted Average | Discounted cash flow    
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Fair Value Inputs, Price Per Millions of BTU | $ / MMBTU 1.73 2.30
Natural gas derivative instruments | Level 3    
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Derivative Assets $ 2,829 $ 4,473
Derivative Liability 1,121 1,142
Parent Company | Electric derivative instruments | Level 3    
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Derivative Assets 3,611 3,044
Derivative Liability 218,639 212,327
Parent Company | Natural gas derivative instruments | Level 3    
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Derivative Assets 2,829 4,473
Derivative Liability $ 1,121 $ 1,142