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Stock options - Computation of weighted average fair value of employee stock options using black-scholes option pricing model assumptions (Detail) - $ / shares
12 Months Ended
Oct. 31, 2019
Oct. 31, 2018
Stock options    
Weighted average volatility 55.42% 46.83%
Expected dividends 0.98% 3.28%
Expected term (in years) 5 years 10 months 24 days 4 years 6 months
Risk-free interest rate 2.86% 1.87%
Weighted average fair value of options granted during the year $ 3.98 $ 0.82
Weighted average fair value of options vested during the year $ 6.03 $ 2.64