Inventories - Additional Information (Detail) - USD ($) $ in Thousands	Jul. 31, 2017	Jul. 31, 2016
Inventory Disclosure [Abstract]
Inventories	$ 494,158	$ 434,004
Subsidiaries valued inventory in last-in, first-out method	284,897	219,050
Subsidiaries valued inventory in first-in, first-out method	209,261	214,954
Inventory obsolescence reserve	$ 5,240	$ 4,840