Goodwill and Intangible Assets - Other Intangible Asset (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Apr. 30, 2013	Jul. 31, 2012
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 348,216	$ 244,493
Accumulated Amortization	(173,633)	(160,374)
Net Book Value	174,583	84,119
Patents [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period	5 years	5 years
Gross Carrying Amount	10,818	10,418
Accumulated Amortization	(9,481)	(9,058)
Net Book Value	1,337	1,360
Trademarks and other [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period	5 years	7 years
Gross Carrying Amount	15,283	8,945
Accumulated Amortization	(7,765)	(7,094)
Net Book Value	7,518	1,851
Customer relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period	8 years	7 years
Gross Carrying Amount	264,501	164,392
Accumulated Amortization	(141,102)	(128,805)
Net Book Value	123,399	35,587
Non-compete agreements and other [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period	4 years	4 years
Gross Carrying Amount	15,681	15,988
Accumulated Amortization	(15,285)	(15,417)
Net Book Value	396	571
Trademarks [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	41,933	44,750
Accumulated Amortization	0	0
Net Book Value	$ 41,933	$ 44,750