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Income Taxes - Additional Information (Detail) - CAD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Disclosure Of Temporary Difference Unused Tax Losses And Unused Tax Credits [Line Items]      
US federal corporate tax rate 21.00% 35.00%  
Deferred income tax expense on revaluation of US federal income tax rate   $ 15,800  
Long-term receivable for alternative minimum tax carryforward balance   2,400  
Loss carryforwards not recognized as deferred incom tax asset $ 37,100    
Unrecognized tax benefits 2,040 1,980 $ 1,923
Interest and penalties included in unrecognized tax benefits 500 500  
Unrecognized tax benefits realized in next twelve months 2,000    
Temporary differences [Member]      
Disclosure Of Temporary Difference Unused Tax Losses And Unused Tax Credits [Line Items]      
Tax effected temporary differences related to US operations $ 33,200 $ 38,800