v3.25.1
Derivative instruments - Fair value of derivative instruments not designated as hedging (Details) - USD ($)
$ in Thousands
Mar. 31, 2025
Dec. 31, 2024
Liabilities    
Derivative Liability, Statement of Financial Position [Extensible Enumeration] Other current liabilities  
Natural gas swaps    
Assets:    
Net Carrying Value Presented on the Balance Sheet $ 59,792 $ 28,624
Liabilities    
Assets 64,222 37,383
Liabilities (4,430) (8,759)
Net Carrying Value Presented on the Balance Sheet 59,792 28,624
Natural gas swaps | Other current assets    
Assets:    
Assets 42,157 19,527
Liabilities (59) (1,563)
Net Carrying Value Presented on the Balance Sheet 42,098 17,964
Natural gas swaps | Other deferred charges    
Assets:    
Assets 22,065 17,566
Liabilities (4,371) (5,279)
Net Carrying Value Presented on the Balance Sheet 17,694 12,287
Natural gas swaps | Other current liabilities    
Liabilities    
Assets 0 290
Liabilities 0 (1,917)
Net Carrying Value Presented on the Balance Sheet 0 (1,627)
Natural gas swaps | Other deferred credits    
Liabilities    
Assets 0 0
Liabilities 0 0
Net Carrying Value Presented on the Balance Sheet $ 0 $ 0