Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	1 Months Ended	3 Months Ended		6 Months Ended			6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended
	Aug. 29, 2008	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2013	Jan. 31, 2012	Jul. 31, 2012	Jan. 31, 2013 Minimum	Jan. 31, 2013 Maximum	Jan. 31, 2013 Stock Option	Jan. 31, 2012 Stock Option	Jan. 31, 2013 Stock Option	Jan. 31, 2012 Stock Option	Jan. 31, 2013 Restricted Stock Units (RSUs)	Oct. 31, 2012 Restricted Stock Units (RSUs)	Jan. 31, 2013 Restricted Stock Units (RSUs)	Jan. 31, 2012 Restricted Stock Units (RSUs)
Product Information [Line Items]
Unrecognized income tax benefits		$ 7,000,000		$ 7,000,000		$ 8,000,000
Unrecognized income tax benefits that would impact impacting income tax rate if recognized		3,500,000		3,500,000		4,400,000
Uncertain tax positions accrued interest and penalties		800,000		800,000		1,000,000
Ownership percentage that trigger limitation on NOL carryforward utilization	50.00%
Operating loss carryforwards, limitations on use	As a result of completion of the Company's merger with Credence Systems Corporation ("Credence") on August 29, 2008, a greater than 50% cumulative ownership change in both entities triggered a significant limitation in net operating loss carryforward utilization. The Company's ability to use operating and acquired net operating loss and credit carryforwards is subject to annual limitation as defined in sections 382 and 383 of the Internal Revenue Code.
Estimated annual limitation on use of net operating loss	10,100,000
Amount of net operating loss able to be used	202,000,000
Share based compensation expense		1,200,000	1,200,000	2,378,000	2,505,000
Restricted stock unit awards granted during period													82,000	793,900
Restricted stock unit award granted vesting period													12 months	4 years
Restricted stock unit award granted vesting percentage														25.00%
Anti-dilutive securities excluded from computation of earnings per share									1,000,000	1,600,000	1,000,000	1,600,000			2,100,000	1,800,000
Maturity period of highly liquid investments to be considered cash equivalent		3 months		3 months
Inventory reserves		42,100,000		42,100,000		42,400,000
Sales of previously reserved inventory		400,000	1,100,000	700,000	5,300,000
Reserves released related to these sales		100,000	200,000	300,000	1,200,000
Property plant and equipment estimated useful life							3 years	7 years
Change in goodwill balance		$ 0	$ 0	$ 0	$ 0
Amortization of intangible assets				1 year 9 months 18 days