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Stock-based compensation and equity transactions - Summary of fair value of employee and non-employee directors’ stock options (Detail)
3 Months Ended
Jan. 31, 2018
Jan. 31, 2017
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]    
Risk-free interest rate 1.87% 0.98%
Dividend yield 3.28% 5.33%
Expected life of the option 4 years 6 months 14 days 3 years 6 months
Volatility factor 46.83% 42.37%