Stockholders' Equity and Stock-based Compensation (Details 2) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended		12 Months Ended
	Apr. 30, 2013		Jul. 31, 2012		Apr. 30, 2013
Stock Option activity under the company's equity incentive plans
Options Outstanding, Number of Stock Options Outstanding Beginning balance	6,486,641
Number of Stock Options Outstanding, Granted in Period	377,412
Number of Stock Options Outstanding, Exercises in Period	(2,653,065)
Number of Stock Options Outstanding, Cancelled in Period	(194,445)
Options Outstanding, Number of Stock Options Outstanding Ending balance	4,016,543		6,486,641
Number of Stock Options Outstanding, Vested and Expected to Vest					3,953,905
Number of Stock Options Outstanding, Exercisable	3,628,247
Weighted-Average Exercise Price Outstanding	$ 6.60		$ 3.74
Weighted-Average Exercise Price Grants in Period	$ 32.36
Weighted-Average Exercise Price, Exercises in Period	$ 2.98
Weighted-Average Exercise Price Cancels in Period	$ 10.58
Weighted-Average Exercise Price, Vested and Expected to Vest					$ 6.40
Weighted-Average Exercise Price, Exercisable	$ 4.34
Weighted Average Remaining Contractual Life, Outstanding	5 years 10 months 13 days		6 years 1 month 13 days
Weighted-Average Remaining Contractual Life, Vested and Expected to Vest	5 years 9 months 29 days
Weighted-Average Remaining Contractual Life, Exercisable	5 years 5 months 14 days
Aggregate Intrinsic Value Beginning balance	$ 142,321	[1]
Aggregate Intrinsic Value Ending balance	134,471	[1]	142,321	[1]
Aggregate Intrinsic Value, Vested and Expected to Vest	133,158	[1]
Aggregate Intrinsic Value, Exercisable	$ 129,663	[1]
Share Price	$ 40.08		$ 25.66
Restricted Stock Units (RSUs)
RSU activity
RSUs Outstanding, Beginning Balance	3,992,177
RSUs Outstanding, Granted	1,697,979
RSUs Outstanding, Released	(1,230,687)
RSUs Outstanding, Cancelled	(296,092)
RSUs Outstanding,Ending Balance	4,163,377
Weighted-Average Grant Date Fair Value Outstanding	$ 8.00				$ 17.48
Weighted-Average Grant Date Fair Value Granted in Period	$ 32.44
Weighted-Average Grant Date Fair Value Vested in Period	$ 9.30
Weighted-Average Grant Date Fair Value Cancelled in Period	$ 15.96

[1] Aggregate intrinsic value represents the difference between the Company's closing stock price of $40.08 and $25.66 on April 30, 2013 and July 31, 2012, respectively, and the exercise price of outstanding, in-the-money options.