Annual report pursuant to Section 13 and 15(d)

Commitments (Details)

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