Summary of Significant Accounting Policies - Computation Of Basic And Diluted Net loss per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Jul. 31, 2012	Apr. 28, 2012	Jan. 28, 2012	Oct. 29, 2011	Jul. 31, 2011	Apr. 30, 2011	Jan. 29, 2011	Oct. 30, 2010	Jul. 31, 2012	Jul. 31, 2011	Jul. 31, 2010
Net loss	$ (2,525)	$ (5,091)	$ (3,694)	$ (1,614)	$ (3,618)	$ (4,136)	$ (3,505)	$ (6,539)	$ (12,924)	$ (17,798)	$ (14,805)
Denominator:
Weighted-average shares of common stock outstanding									28,807	28,567	28,432
Weighted-average shares subject to repurchase											(10)
Shares used in per-share calculation-basic									28,807	28,567	28,422
Basic									28,807	28,567	28,422
Weighted common stock equivalents
Shares used in per-share calculation-diluted									28,807	28,567	28,422
Net loss per share:
Basic									$ (0.45)	$ (0.62)	$ (0.52)
Diluted									$ (0.45)	$ (0.62)	$ (0.52)