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Financial risk management - Additional Information (Detail)
 12 Months Ended
Dec. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Dec. 10, 2012
Disclosure of risk management [line items]      
Increase/decrease in the U.S. dollar exchange rate against all currencies except Canadian dollar, Australian dollar, Euro, Turkish lira, Chinese renminbi, Swedish krona, Romanian lei, Great British pound and Brazilian real 1.00%    
Decrease/increase in profit (loss) before taxes due to 1% increase/decrease in the U.S. dollar exchange rate against all currencies except Canadian dollar, Australian dollar, Euro, Turkish lira, Chinese renminbi, Swedish krona, Romanian lei, Great British pound and Brazilian real $ 675,000 $ 25,000  
Decrease/increase in other comprehensive income due to 1% increase/decrease in the U.S. dollar exchange rate against all currencies except Canadian dollar, Australian dollar, Euro, Turkish lira, Chinese renminbi, Swedish krona, Romanian lei, Great British pound and Brazilian real 0    
Maximum exposure to credit risk $ 356,823,000    
Number of days from shipment 15 days    
Debt to capital ratio 15.20% 13.80%  
Senior notes [member]      
Disclosure of risk management [line items]      
Debt fixed interest rate     6.125%
Revolving credit facility [member]      
Disclosure of risk management [line items]      
Net Debt to EBITDA ratio 2.26 0.9