Goodwill and Intangible Assets - Other Intangibles Assets (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Apr. 30, 2015	Apr. 30, 2014	Apr. 30, 2015	Apr. 30, 2014	Jul. 31, 2014
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
Amortization of Intangible Assets	$ 2,900	$ 4,713	$ 9,251	$ 14,837
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	11,768		11,768
Finite-Lived Intangible Assets, Amortization Expense, Year Two	9,670		9,670
Finite-Lived Intangible Assets, Amortization Expense, Year Three	7,388		7,388
Finite-Lived Intangible Assets, Amortization Expense, Year Four	6,634		6,634
Finite-Lived Intangible Assets, Amortization Expense, Year Five	6,352		6,352
Other Intangible Assets [Line Items]
Gross Carrying Amount	203,093		203,093		235,865
Accumulated Amortization	(124,329)		(124,329)		(144,851)
Net Book Value	78,764		78,764		91,014
Patents [Member]
Other Intangible Assets [Line Items]
Weighted Average Amortization Period			5 years		5 years
Gross Carrying Amount	11,889		11,889		11,656
Accumulated Amortization	(10,503)		(10,503)		(10,160)
Net Book Value	1,386		1,386		1,496
Trademarks And Other [Member]
Other Intangible Assets [Line Items]
Weighted Average Amortization Period			5 years		5 years
Gross Carrying Amount	14,492		14,492		15,366
Accumulated Amortization	(11,938)		(11,938)		(10,706)
Net Book Value	2,554		2,554		4,660
Customer relationships [Member]
Other Intangible Assets [Line Items]
Weighted Average Amortization Period			7 years		7 years
Gross Carrying Amount	138,486		138,486		168,525
Accumulated Amortization	(92,575)		(92,575)		(114,363)
Net Book Value	45,911		45,911		54,162
Non-compete agreements and other [Member]
Other Intangible Assets [Line Items]
Weighted Average Amortization Period			4 years		4 years
Gross Carrying Amount	9,383		9,383		10,089
Accumulated Amortization	(9,313)		(9,313)		(9,622)
Net Book Value	70		70		467
Trademarks [Member]
Other Intangible Assets [Line Items]
Gross Carrying Amount	28,843		28,843		30,229
Accumulated Amortization	0		0		0
Net Book Value	$ 28,843		$ 28,843		$ 30,229