Goodwill and Intangible Assets - Other Intangibles Assets (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2016	Apr. 30, 2015	Jul. 31, 2015
Other Intangible Assets [Line Items]
Gross Carrying Amount	$ 196,751		$ 196,751		$ 195,569
Accumulated Amortization	(134,491)		(134,491)		(126,681)
Net Book Value	62,260		62,260		$ 68,888
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Amortization of Intangible Assets	1,838	$ 2,900	7,066	$ 9,251
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	8,881		8,881
Finite-Lived Intangible Assets, Amortization Expense, Year Two	7,175		7,175
Finite-Lived Intangible Assets, Amortization Expense, Year Three	6,471		6,471
Finite-Lived Intangible Assets, Amortization Expense, Year Four	6,181		6,181
Finite-Lived Intangible Assets, Amortization Expense, Year Five	5,628		$ 5,628
Patents [Member]
Other Intangible Assets [Line Items]
Weighted Average Amortization Period			5 years		5 years
Gross Carrying Amount	12,218		$ 12,218		$ 12,073
Accumulated Amortization	(10,989)		(10,989)		(10,641)
Net Book Value	1,229		$ 1,229		$ 1,432
Trademarks And Other [Member]
Other Intangible Assets [Line Items]
Weighted Average Amortization Period			5 years		5 years
Gross Carrying Amount	14,459		$ 14,459		$ 14,375
Accumulated Amortization	(13,713)		(13,713)		(12,471)
Net Book Value	746		$ 746		$ 1,904
Customer relationships [Member]
Other Intangible Assets [Line Items]
Weighted Average Amortization Period			7 years		7 years
Gross Carrying Amount	137,520		$ 137,520		$ 136,693
Accumulated Amortization	(100,621)		(100,621)		(94,537)
Net Book Value	36,899		$ 36,899		$ 42,156
Non-compete agreements and other [Member]
Other Intangible Assets [Line Items]
Weighted Average Amortization Period			4 years		4 years
Gross Carrying Amount	9,184		$ 9,184		$ 9,076
Accumulated Amortization	(9,168)		(9,168)		(9,032)
Net Book Value	16		16		44
Trademarks [Member]
Other Intangible Assets [Line Items]
Gross Carrying Amount	23,370		23,370		23,352
Accumulated Amortization	0		0		0
Net Book Value	$ 23,370		$ 23,370		$ 23,352