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Share-based payments - Summary of Assumptions Used to Estimate the Fair Value of Options Granted (Detail)
12 Months Ended
Dec. 31, 2018
CAD ($)
yr
Dec. 31, 2017
CAD ($)
yr
Disclosure of range of exercise prices of outstanding share options [line items]    
Expected dividends (CDN$) | $ $ 0.00 $ 0.02
Forfeiture rate (%) 8.00% 11.00%
Bottom of range [member]    
Disclosure of range of exercise prices of outstanding share options [line items]    
Risk-free interest rate (range) (%) 1.80% 0.70%
Expected volatility (range) (%) 58.00% 60.00%
Expected life (range) (years) 1.79 1.80
Top of range [member]    
Disclosure of range of exercise prices of outstanding share options [line items]    
Risk-free interest rate (range) (%) 2.20% 1.05%
Expected volatility (range) (%) 64.00% 65.00%
Expected life (range) (years) 3.79 3.80