Property, Plant and Equipment - Additional Information (Detail) (USD $)	1 Months Ended	12 Months Ended			0 Months Ended	12 Months Ended	1 Months Ended
	Jul. 28, 2010	Jul. 31, 2012	Jul. 31, 2011	Jul. 31, 2010	Oct. 23, 2009 San Juan [Member]	Jul. 31, 2010 San Juan [Member]	Jul. 31, 2010 Piscataway [Member]	Jul. 28, 2010 Piscataway [Member]
Property, Plant and Equipment [Line Items]
Carrying value of the land, building and improvements		$ 43,300,000
Mortgage payable		22,900,000
Proceeds from insurance			3,500,000	500,000
Damaged portion of building and improvements			1,100,000
Gain from insurance claim			2,637,000
Sale of land and building	3,100,000		100,000	5,270,000	7,400,000			3,100,000
Transaction expenses						800,000
Mortgage payable secured by property								2,700,000
Gain on sale of asset							700,000
Property, plant and equipment under capital leases		0	25,100,000
Accumulated depreciation			25,100,000
Depreciation and amortization expense		$ 15,900,000	$ 20,100,000	$ 30,600,000