Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Jul. 31, 2012	Jul. 31, 2011	Jul. 31, 2010	Jul. 31, 2009
Income Tax Contingency [Line Items]
Deferred tax assets, valuation allowance	$ 332,748,000	$ 328,277,000
Change in Deferred tax valuation allowance	4,500,000	700,000
Net operating loss carry forwards, stock option deductions	125,000,000
Benefits of stock option deductions	47,800,000
Net operating loss carry forwards related to the exercise of stock option	7,100,000
Excess tax benefit transferred to additional paid in capital	2,700,000
Total unrecognized tax benefit	1,673,000	1,702,000	1,568,000	1,349,000
Unrecognized tax benefit uncertain tax position	500,000	400,000
Federal
Income Tax Contingency [Line Items]
Net operating loss carry forwards	815,600,000
Research and development credit carry forwards	11,200,000
State and Local Jurisdiction
Income Tax Contingency [Line Items]
Net operating loss carry forwards	151,900,000
Research and development credit carry forwards	$ 10,300,000