Restructuring Charges - Additional Information (Detail) (USD $)	3 Months Ended	12 Months Ended
	Oct. 29, 2011	Jul. 31, 2012	Jul. 31, 2010
Restructuring Cost and Reserve [Line Items]
Reversed balance of a reserve for the consolidation		$ (227,000)
Restructuring charge for cost of product revenue	(271,000)	(271,000)	5,625,000
Cost Of Sales [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charge for cost of product revenue		300,000
Operating Expense [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charge for cost of product revenue			5,600,000
Cost Of Product Revenue [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charge for cost of product revenue			100,000
Employee separation cost			100,000
Contract Termination [Member]
Restructuring Cost and Reserve [Line Items]
Employee separation cost			3,200,000
Facilities Consolidation [Member]
Restructuring Cost and Reserve [Line Items]
Employee separation cost			3,100,000
New Jersey Facility [Member]
Restructuring Cost and Reserve [Line Items]
Other restructuring cost			1,900,000
Massachusetts Facility [Member]
Restructuring Cost and Reserve [Line Items]
Reversed balance of a reserve for the consolidation	200,000
Other restructuring cost			$ 600,000