Cash dividend and declared dividends - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Oct. 31, 2016	Jul. 31, 2016	Apr. 30, 2016	Jan. 31, 2016	Oct. 31, 2015	Jul. 31, 2015	Apr. 30, 2015	Jan. 31, 2015	Oct. 31, 2016	Oct. 31, 2015
Dividends Payable [Line Items]
Dividends paid, per share	$ 0.02	$ 0.02	$ 0.02	$ 0.07	$ 0.07	$ 0.07	$ 0.07	$ 0.07
Dividends paid									$ 1,141	$ 2,382