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Summary of fair value of employee and non-employee directors’ stock options (Detail)
9 Months Ended
Jul. 31, 2017
Jul. 31, 2016
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]    
Risk-free interest rate 1.20% 0.70%
Dividend yield 5.00% 2.38%
Expected life of the option 4 years 3 months 22 days 3 years
Volatility factor 43.30% 28.70%