Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2014
Income Tax Contingency [Line Items]
Valuation allowance increased amount	$ 11,500,000	$ 23,100,000
Credit carryforwards	224,100,000	193,300,000
Income tax provided on undistributed earnings and other outside basis differences of foreign subsidiaries	0
Undistributed earnings and other outside basis differences of foreign subsidiaries	4,000,000
Unrecognized tax benefits potentially affect effective income tax rate if recognized	200,000
Interest and penalties recorded charges to tax expense	33,000	36,000	$ 39,000
Accrued interest and penalties	400,000	500,000
Federal Income Tax [Member] | R&D Credit Carryforwards [Member]
Income Tax Contingency [Line Items]
Credit carryforwards	$ 5,000,000	3,100,000
Federal Income Tax [Member] | Earliest Tax Year [Member]
Income Tax Contingency [Line Items]
Operating loss carryforwards expiration year	2024
Federal Income Tax [Member] | Earliest Tax Year [Member] | R&D Credit Carryforwards [Member]
Income Tax Contingency [Line Items]
Tax credit loss carryforwards expiration year	2024
California State Income Tax [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	$ 80,400,000	162,500,000
California State Income Tax [Member] | R&D Credit Carryforwards [Member]
Income Tax Contingency [Line Items]
Credit carryforwards	$ 2,900,000	$ 4,200,000
California State Income Tax [Member] | Earliest Tax Year [Member]
Income Tax Contingency [Line Items]
Operating loss carryforwards expiration year	2016