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Income taxes - Additional Information (Detail) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2020
Jun. 30, 2020
Jun. 30, 2019
Income Tax Disclosure [Abstract]      
Canadian enacted statutory rate (percent)   26.50% 26.50%
U.S. Tax reform and related deferred tax adjustments $ 9,300