Annual report pursuant to Section 13 and 15(d)

Commitments (Details)

Commitments (Details) - USD ($)
$ in Thousands
12 Months Ended
Jul. 31, 2017
Jul. 31, 2016
Jul. 31, 2015
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 2017 and June 2028. 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 addition to the minimumannual rentals of space, the lease is subject to annual increases, based on the consumer price index. Annual increases are limitedto 3% per year.    
Maximum Annual Rental Increase Percentage 3.00%    
Rent expense Including Real Estate Taxes $ 1,752 $ 1,704 $ 1,623
Amount of Real Estate Tax Abatement Received   61 61
Operating Leases, Rent Expense 4,658 $ 4,572 $ 4,504
Operating Leases, Rent Expense, Sublease Rentals $ 323    
Agreement Renew Period 2 years    
Other Commitment, Due in Next Twelve Months $ 2,498    
Minimum [Member]      
Commitments (Details) [Line Items]      
Lease Expiration Month and Year September 2017    
Maximum [Member]      
Commitments (Details) [Line Items]      
Lease Expiration Month and Year June 2028