Income taxes (Detail) (USD $)	Jul. 31, 2012	Jul. 31, 2011
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	$ 86,900,000
Deferred Tax Assets Research And Development And Other Tax Credit Carryforwards	795,000	633,000
Foreign Loss Carryforwards	400,000
Operating Loss Carryforwards On Acquisitions	1,100,000
Undistributed Earnings of Foreign Subsidiaries	164,000
U.S. Federal Tax [Member]
Deferred Tax Assets Research And Development And Other Tax Credit Carryforwards	$ 700,000