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Cash dividend and declared dividends - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended 6 Months Ended
Apr. 30, 2017
Apr. 30, 2016
Apr. 30, 2017
Apr. 30, 2016
Dividends Payable [Line Items]        
Dividends paid, per share $ 0.02 $ 0.02 $ 0.04  
Dividends paid $ 177 $ 177 $ 353 $ 787
Maximum [Member]        
Dividends Payable [Line Items]        
Dividends paid, per share       $ 0.07
Minimum [Member]        
Dividends Payable [Line Items]        
Dividends paid, per share       $ 0.02