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Financial instruments - North american natural gas forward contracts (Details)
MMBTU in Thousands
 12 Months Ended
Dec. 31, 2023
USD ($)
MMBTU
Dec. 31, 2022
USD ($)
MMBTU
Accumulated other comprehensive income    
Disclosure of financial assets [line items]    
Reclassification of hedge gain (loss) in cash flow hedge $ (22,500,000) $ 55,000,000
North american natural gas forward contract    
Disclosure of financial assets [line items]    
Hedge ineffectiveness $ 0 $ 0
North american natural gas forward contract | Cash flow hedges    
Disclosure of financial assets [line items]    
Hedging instrument, energy (in mmbtu) | MMBTU 347,190 307,900
Notional amount $ 1,183,319,000 $ 1,014,264,000
Assets, fair value 29,925,000 316,008,000
North american natural gas forward contract | Cash flow hedges | Other current assets    
Disclosure of financial assets [line items]    
Assets, fair value 470,000 32,768,000
North american natural gas forward contract | Cash flow hedges | Other non-current assets    
Disclosure of financial assets [line items]    
Assets, fair value 120,638,000 289,979,000
North american natural gas forward contract | Cash flow hedges | Other current liabilities    
Disclosure of financial assets [line items]    
Liabilities, fair value (60,532,000) (317,000)
North american natural gas forward contract | Cash flow hedges | Other long-term liabilities    
Disclosure of financial assets [line items]    
Liabilities, fair value $ (30,651,000) $ (6,422,000)
North american natural gas forward contract | Cash flow hedges | Bottom of range    
Disclosure of financial assets [line items]    
Hedging instrument, daily energy annualized (in mmbtu) | MMBTU 50 50
North american natural gas forward contract | Cash flow hedges | Top of range    
Disclosure of financial assets [line items]    
Hedging instrument, daily energy annualized (in mmbtu) | MMBTU 170 150