Goodwill and Intangible Assets - Other Intangibles Assets (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2017	Jan. 31, 2016	Jul. 31, 2016
Other Intangible Assets [Line Items]
Gross Carrying Amount	$ 192,635		$ 192,635		$ 194,550
Accumulated Amortization	(136,655)		(136,655)		(134,744)
Net Book Value	55,980		55,980		$ 59,806
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Amortization of Intangible Assets	1,688	$ 2,595	3,583	$ 5,228
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	7,356		7,356
Finite-Lived Intangible Assets, Amortization Expense, Year Two	6,680		6,680
Finite-Lived Intangible Assets, Amortization Expense, Year Three	6,412		6,412
Finite-Lived Intangible Assets, Amortization Expense, Year Four	5,909		5,909
Finite-Lived Intangible Assets, Amortization Expense, Year Five	5,864		$ 5,864
Patents [Member]
Other Intangible Assets [Line Items]
Weighted Average Amortization Period			5 years		5 years
Gross Carrying Amount	12,283		$ 12,283		$ 12,252
Accumulated Amortization	(11,278)		(11,278)		(11,063)
Net Book Value	1,005		$ 1,005		$ 1,189
Trademarks And Other [Member]
Other Intangible Assets [Line Items]
Weighted Average Amortization Period			5 years		5 years
Gross Carrying Amount	14,252		$ 14,252		$ 14,359
Accumulated Amortization	(13,720)		(13,720)		(13,709)
Net Book Value	532		$ 532		$ 650
Customer relationships [Member]
Other Intangible Assets [Line Items]
Weighted Average Amortization Period			7 years		7 years
Gross Carrying Amount	134,209		$ 134,209		$ 135,795
Accumulated Amortization	(102,539)		(102,539)		(100,830)
Net Book Value	31,670		$ 31,670		$ 34,965
Non-compete agreements and other [Member]
Other Intangible Assets [Line Items]
Weighted Average Amortization Period			4 years		4 years
Gross Carrying Amount	9,118		$ 9,118		$ 9,153
Accumulated Amortization	(9,118)		(9,118)		(9,142)
Net Book Value	0		0		11
Trademarks [Member]
Other Intangible Assets [Line Items]
Gross Carrying Amount	22,773		22,773		22,991
Accumulated Amortization	0		0		0
Net Book Value	$ 22,773		$ 22,773		$ 22,991