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Income taxes - Additional Information (Detail) - USD ($)
$ in Thousands
12 Months Ended
Jun. 01, 2018
Dec. 31, 2018
Dec. 31, 2017
Income Tax Disclosure [Abstract]      
Canadian enacted statutory rate   26.50% 26.50%
U.S. Tax reform and related deferred tax adjustments $ (15,586) $ 18,363 $ (17,112)
Valuation allowance for deferred tax assets   28,018 $ 19,951
Deferred income taxes, undistributed earnings of foreign subsidiaries   $ 280,643