Share-Based Compensation - Stock Option Activity (Detail) (USD $)	3 Months Ended	12 Months Ended
	Oct. 27, 2012	Jul. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercisable, Weighted Average Contractual Term (Years)	5 years 9 months 4 days
Options vested and expected to vest, Weighted Average Contractual Term (Years)	5 years 8 months 19 days
Options exercisable as of October 27, 2012, Weighted Average Contractual Term (Years)	4 years 11 months 27 days	6 years 11 days
Beginning balance, Weighted Average Exercise Price	$ 7.29
Options granted, Weighted Average Exercise Price
Options exercised, Weighted Average Exercise Price	$ 13.22
Options cancelled, Weighted Average Exercise Price	$ 12.09
Ending balance, Weighted Average Exercise Price	$ 7.09	$ 7.29
Options vested and expected to vest, Weighted Average Exercise Price	$ 7.09
Options exercisable as of October 27, 2012, Weighted Average Exercise Price	$ 7.05
Beginning balance, Number of Shares	5,864,330
Options granted, Number of Shares
Options exercised, Number of Shares	(2,800)
Options cancelled, Number of Shares	(226,780)
Ending balance, Number of Shares	5,634,750	5,864,330
Options vested and expected to vest , Number of Shares	5,555,162
Options exercisable as of October 27, 2012, Number of Shares	4,308,147