Summary of Stock Option Activity Under All Plans (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Oct. 29, 2011 Year
Number of Shares
Number of Shares outstanding-beginning of period	6,914,800
Number of Shares, Granted	1,462,500
Number of Shares, Exercised	(114,800)
Number of Shares, Cancelled/Forfeited	(59,600)
Number of Shares outstanding-end of period	8,202,900
Number of Shares vested and expected to vest at end of period	7,860,000	[1]
Number of Shares exercisable at end of period	4,007,100
Weighted-Average Exercise Price
Weighted-Average Exercise Price, beginning of period	$ 16.93
Weighted-Average Exercise Price, Granted	$ 26.23
Weighted-Average Exercise Price, Exercised	$ 13.74
Weighted-Average Exercise Price, Cancelled/Forfeited	$ 21.55
Weighted-Average Exercise Price, end of period	$ 18.60
Weighted-Average Exercise Price vested and expected to vest at end of period	$ 19.41	[1]
Weighted-Average Exercise Price exercisable at end of period	$ 14.05
Weighted-Average Remaining Contractual Terms (years)
Weighted-Average Remaining Contractual Terms, beginning of period	6.4
Weighted-Average Remaining Contractual Terms, end of period	6.9
Weighted-Average Remaining Contractual Terms, vested and expected to vest at end of period	6.8	[1]
Weighted-Average Remaining Contractual Terms, exercisable at end of period	4.9
Aggregate Intrinsic Value
Aggregate Intrinsic Value, beginning of period	$ 106.4	[2]
Aggregate Intrinsic Value, end of period	95.4	[2]
Aggregate Intrinsic Value, vested and expected to vest at end of period	92.8	[1],[2]
Aggregate Intrinsic Value, exercisable at end of period	$ 64.7	[2]

[1] The number of options expected to vest takes into consideration estimated expected forfeitures.

[2] The intrinsic value is the amount by which the market price at the end of the period of the underlying share of stock exceeds the exercise price of the stock option.