Weighted-Average Grant Date Fair Value of Employee Stock Options Granted (Detail)	12 Months Ended
	Jul. 31, 2012	Jul. 31, 2011	Jul. 31, 2010	Jul. 31, 2009
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Expected volatility	59.56%	62.64%	65.77%	56.64%
Risk-free interest rate	0.84%	0.99%	1.88%	2.34%
Expected term (in years)	4 years 7 months 28 days	4 years 3 months 7 days	4 years 29 days	4 years 29 days
Expected dividend yield	0.00%	0.00%	0.00%	0.00%