Goodwill and Intangible Assets - Other Intangibles Assets (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Apr. 30, 2017	Apr. 30, 2016	Apr. 30, 2017	Apr. 30, 2016	Jul. 31, 2016
Other Intangible Assets [Line Items]
Gross Carrying Amount	$ 192,968		$ 192,968		$ 194,550
Accumulated Amortization	(138,861)		(138,861)		(134,744)
Net Book Value	54,107		54,107		$ 59,806
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Amortization of Intangible Assets	1,766	$ 1,838	5,349	$ 7,066
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	6,869		6,869
Finite-Lived Intangible Assets, Amortization Expense, Year Two	6,158		6,158
Finite-Lived Intangible Assets, Amortization Expense, Year Three	5,936		5,936
Finite-Lived Intangible Assets, Amortization Expense, Year Four	5,431		5,431
Finite-Lived Intangible Assets, Amortization Expense, Year Five	5,385		$ 5,385
Patents [Member]
Other Intangible Assets [Line Items]
Weighted Average Amortization Period			5 years		5 years
Gross Carrying Amount	12,337		$ 12,337		$ 12,252
Accumulated Amortization	(11,410)		(11,410)		(11,063)
Net Book Value	927		$ 927		$ 1,189
Trademarks And Other [Member]
Other Intangible Assets [Line Items]
Weighted Average Amortization Period			5 years		5 years
Gross Carrying Amount	14,328		$ 14,328		$ 14,359
Accumulated Amortization	(13,864)		(13,864)		(13,709)
Net Book Value	464		$ 464		$ 650
Customer relationships [Member]
Other Intangible Assets [Line Items]
Weighted Average Amortization Period			7 years		7 years
Gross Carrying Amount	134,618		$ 134,618		$ 135,795
Accumulated Amortization	(104,496)		(104,496)		(100,830)
Net Book Value	30,122		$ 30,122		$ 34,965
Non-compete agreements and other [Member]
Other Intangible Assets [Line Items]
Weighted Average Amortization Period			4 years		4 years
Gross Carrying Amount	9,091		$ 9,091		$ 9,153
Accumulated Amortization	(9,091)		(9,091)		(9,142)
Net Book Value	0		0		11
Trademarks [Member]
Other Intangible Assets [Line Items]
Gross Carrying Amount	22,594		22,594		22,991
Accumulated Amortization	0		0		0
Net Book Value	$ 22,594		$ 22,594		$ 22,991