Property, Plant and Equipment - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Oct. 31, 2016	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2015
Property, Plant and Equipment [Line Items]
Property, plant and equipment		$ 590,675	$ 480,436
Accumulated depreciation		165,437	136,169
Net cash proceeds from land and buildings and improvements	$ 4,254	4,682	347	$ 381
Gain on the sale of land and buildings and improvements	$ 2,165	2,231	35	$ 91
Assets Held under Capital Leases
Property, Plant and Equipment [Line Items]
Property, plant and equipment		6,527	6,527
Accumulated depreciation		$ 1,224	$ 680