Deferred Tax Assets and Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Jul. 31, 2014	Jul. 31, 2013
Deferred tax assets:
Net operating loss carryforwards	$ 148,155	$ 144,399
Capital loss carryforwards	418	393
Tax credits	29,033	26,965
Inventory valuation reserves	20,635	20,694
Deferred revenue	1,615	648
Fixed assets and spares		14
Other	13,223	13,018
Total deferred tax assets	213,079	206,131
Valuation allowance	(211,925)	(204,484)
Net deferred tax assets	1,154	1,647
Deferred tax liabilities:
Intangibles	(1,078)
Fixed assets and spares	(509)	(1,212)
Prepaid expenses	(32)	(22)
Other	(58)	(413)
Total deferred tax liabilities	(1,677)	(1,647)
Net deferred tax assets (liabilities)	$ (523)