Inventory - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jul. 31, 2017	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2015
Inventory Disclosure [Abstract]
Excess and obsolescence charge related to the write-downs of inventory	$ 8,300	$ 9,246	$ 1,354	$ 2,391