v3.26.1
Fair Value (Narrative) (Details) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Dec. 31, 2025
Dec. 31, 2024
Fair Value, Option, Quantitative Disclosures [Line Items]        
Investments, Fair Value Disclosure $ 4,575 $ 4,428    
Asset Retirement Obligation, Revision of Estimate (4,589) (12,919)    
Asset retirement obligations, non-current 511,366 322,883 $ 532,463  
Unamortized deferred financing costs 35,800   36,500  
Unamortized debt discount 10,100   10,300  
Financial Transmission Rights Fair Value Disclosure 551 1,584    
Assets, Fair Value Disclosure 5,126 6,012    
Derivative Financial Instruments, Liabilities        
Fair Value, Option, Quantitative Disclosures [Line Items]        
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value 551 398 $ 1,584 $ 1,526
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements (1,033) (1,128)    
Money Market Funds [Member]        
Fair Value, Option, Quantitative Disclosures [Line Items]        
Investments, Fair Value Disclosure 129 104    
Mutual Fund [Member]        
Fair Value, Option, Quantitative Disclosures [Line Items]        
Investments, Fair Value Disclosure 4,446 4,324    
Fair Value, Inputs, Level 3 [Member]        
Fair Value, Option, Quantitative Disclosures [Line Items]        
Investments, Fair Value Disclosure 0 0    
Financial Transmission Rights Fair Value Disclosure 551 1,584    
Assets, Fair Value Disclosure 551 1,584    
Fair Value, Inputs, Level 3 [Member] | Money Market Funds [Member]        
Fair Value, Option, Quantitative Disclosures [Line Items]        
Investments, Fair Value Disclosure 0 0    
Fair Value, Inputs, Level 3 [Member] | Mutual Fund [Member]        
Fair Value, Option, Quantitative Disclosures [Line Items]        
Investments, Fair Value Disclosure 0 0    
Fair Value, Inputs, Level 2 [Member]        
Fair Value, Option, Quantitative Disclosures [Line Items]        
Investments, Fair Value Disclosure 0 0    
Financial Transmission Rights Fair Value Disclosure 0 0    
Assets, Fair Value Disclosure 0 0    
Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member]        
Fair Value, Option, Quantitative Disclosures [Line Items]        
Investments, Fair Value Disclosure 0 0    
Fair Value, Inputs, Level 2 [Member] | Mutual Fund [Member]        
Fair Value, Option, Quantitative Disclosures [Line Items]        
Investments, Fair Value Disclosure 0 0    
Fair Value, Inputs, Level 1 [Member]        
Fair Value, Option, Quantitative Disclosures [Line Items]        
Investments, Fair Value Disclosure 4,575 4,428    
Financial Transmission Rights Fair Value Disclosure 0 0    
Assets, Fair Value Disclosure 4,575 4,428    
Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]        
Fair Value, Option, Quantitative Disclosures [Line Items]        
Investments, Fair Value Disclosure 129 104    
Fair Value, Inputs, Level 1 [Member] | Mutual Fund [Member]        
Fair Value, Option, Quantitative Disclosures [Line Items]        
Investments, Fair Value Disclosure $ 4,446 $ 4,324