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Equity - Summary of Weighted Average Assumptions (Detail)
12 Months Ended
Dec. 31, 2017
CAD
yr
Dec. 31, 2016
CAD
yr
Disclosure of terms and conditions of share-based payment arrangement [abstract]    
Weighted average exercise price | CAD CAD 27.79 CAD 5.48
Dividend yield 2.20% 1.85%
Risk-free interest rate 1.06% 0.72%
Expected option life | yr 4.2 4.2
Expected volatility 42.00% 46.00%
Forfeiture rate 0.36% 0.96%