Commitments (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2012
Commitments (Details) [Line Items]
Description Of Operating Leases	The Company leases equipment, office and laboratory space under several non-cancelable operating leases that expire between September 2014 and May 2023. Certain leases include renewal options and rent escalation clauses. An entity owned by certain executive officers/directors of the Company owns the building that the Company leases as its main facility for laboratory operations and certain research operations. In March 2005, the Company amended and extended the lease for 12 years. In addition to the minimum annual rentals of space, the lease is subject to annual increases, based on the consumer price index. Annual increases are limited to 3% per year
Lease Extension Period	12 years
Maximum Annual Rental Increase Percentage	3.00%
Rent expense Including Real Estate Taxes	$ 1,649	$ 1,605	$ 1,556
Operating Leases, Rent Expense	4,488	4,354	4,378
Operating Leases, Rent Expense, Sublease Rentals	322
Agreement Renew Period	2 years
Other Commitment, Due in Next Twelve Months	$ 2,271
Minimum [Member]
Commitments (Details) [Line Items]
Lease Expiration Month and Year	September 2014
Maximum [Member]
Commitments (Details) [Line Items]
Lease Expiration Month and Year	May 2023