Commitments (Details) - USD ($) $ in Thousands	12 Months Ended
	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2014
Commitments (Details) [Line Items]
Description Of Operating Leases	The Company leases equipment, office and laboratory space underseveral non-cancellable operating leases that expire between September 2015 and May 2023. Certain leases include renewal optionsand rent escalation clauses. An entity owned by certain executive officers/directors of the Company owns the building that theCompany leases as its main facility for clinical laboratory operations and certain research operations. In March 2005, the Companyamended and extended the lease for 12 years. In addition to the minimum annual rentals of space, the lease is subject to annualincreases, 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	$ 1,704	$ 1,623	$ 1,649
Amount of Real Estate Tax Abatement Received		61
Operating Leases, Rent Expense	4,572	$ 4,504	$ 4,488
Operating Leases, Rent Expense, Sublease Rentals	$ 323
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 2015
Maximum [Member]
Commitments (Details) [Line Items]
Lease Expiration Month and Year	May 2023