Acquisitions - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Jul. 31, 2015	Jul. 31, 2014	Jul. 31, 2013
Business Acquisition Actual Revenue And Pre Tax Income Loss [Line Items]
Interest expense	$ 11,156	$ 14,300	$ 16,641
Income tax expense (benefit)	20,093	(4,963)	42,583
Pre-tax amortization of intangible assets	$ 12,103	17,871	$ 17,148
Precision Dynamics Corporation [Member]
Business Acquisition Actual Revenue And Pre Tax Income Loss [Line Items]
Proceeds from borrowing on notes payable		220,000
Business Combination, Acquisition related costs		3,600
Business Combination, Non-recurring adjustment, Inventory		1,530
Interest expense		529
Income tax expense (benefit)		(429)
Pre-tax amortization of intangible assets		$ 5,215