Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Jul. 31, 2015	Jul. 31, 2014	Jul. 31, 2013
Schedule Of Income Taxes [Line Items]
Deferred tax assets, valuation allowance	$ 326,065	$ 325,567
Net operating loss carry forwards, stock option deductions	125,000
Benefits of stock option deductions	47,800
Net operating loss carry forwards related to exercise of stock option	7,100
Total unrecognized tax benefit	1,587	1,786	$ 1,742
Unrecognized tax benefit uncertain tax position	600	$ 600
Minimum
Schedule Of Income Taxes [Line Items]
Unrecognized tax benefit, reasonably possible liability reduction	500
Maximum
Schedule Of Income Taxes [Line Items]
Unrecognized tax benefit, reasonably possible liability reduction	700
Federal
Schedule Of Income Taxes [Line Items]
Net operating loss carry forwards	$ 857,760
Operating Loss Carry forwards Expiration Year	2034
Research and development credit carry forwards	$ 11,320
Research and Development Credit Carry forwards Expiration Year	2020
State and Local Jurisdiction
Schedule Of Income Taxes [Line Items]
Net operating loss carry forwards	$ 36,200
Operating Loss Carry forwards Expiration Year	2034
Research and development credit carry forwards	$ 9,980
Research and Development Credit Carry forwards Expiration Year	2016