Annual report pursuant to Section 13 and 15(d)

Summary of significant accounting policies (Details)

v3.10.0.1
Summary of significant accounting policies (Details)
 12 Months Ended
Jul. 31, 2018
USD ($)
shares
Jul. 31, 2017
USD ($)
shares
Jul. 31, 2016
USD ($)
shares
Jul. 31, 2015
USD ($)
Summary of significant accounting policies (Details) [Line Items]        
Number of Operating Segments 3      
Cash and Cash Equivalents, at Carrying Value $ 60,041,000 $ 64,167,000 $ 67,777,000 $ 18,109,000
Contractual Adjustment Percentage 85.00% 84.00% 84.00%  
Percentage of Doubtful Accounts to Accounts Receivable 16.90% 19.10%    
Finite-Lived Intangible Asset, Useful Life 10 years      
Impairment of Long-Lived Assets Held-for-use $ 0 $ 0 $ 0  
Advertising Expense 580,000 649,000 $ 601,000  
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in Shares) | shares     449,000  
Share-based Compensation 813,000 831,000 $ 525,000  
Excess Tax Benefit from Share-based Compensation, Operating Activities 0 0 $ 0  
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options $ 1,138,000      
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition 24 months      
Foreign Bank [Member]        
Summary of significant accounting policies (Details) [Line Items]        
Cash and Cash Equivalents, at Carrying Value $ 400,000 $ 500,000    
Minimum [Member]        
Summary of significant accounting policies (Details) [Line Items]        
Finite-Lived Intangible Asset, Useful Life 4 years      
Minimum [Member] | Building and Building Improvements [Member]        
Summary of significant accounting policies (Details) [Line Items]        
Property, Plant and Equipment, Useful Life 15 years      
Minimum [Member] | Machinery and Equipment [Member]        
Summary of significant accounting policies (Details) [Line Items]        
Property, Plant and Equipment, Useful Life 3 years      
Maximum [Member]        
Summary of significant accounting policies (Details) [Line Items]        
Finite-Lived Intangible Asset, Useful Life 15 years      
Maximum [Member] | Building and Building Improvements [Member]        
Summary of significant accounting policies (Details) [Line Items]        
Property, Plant and Equipment, Useful Life 30 years      
Maximum [Member] | Machinery and Equipment [Member]        
Summary of significant accounting policies (Details) [Line Items]        
Property, Plant and Equipment, Useful Life 10 years      
Unvested Restricted Stock [Member] | In the Money Stock Options [Member]        
Summary of significant accounting policies (Details) [Line Items]        
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in Shares) | shares 624,000 961,000    
Outstanding Options [Member]        
Summary of significant accounting policies (Details) [Line Items]        
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in Shares) | shares 291,000 0 282,000  
Accounts Payable [Member]        
Summary of significant accounting policies (Details) [Line Items]        
Concentration Risk, Percentage 12.00%      
Accounts Receivable [Member]        
Summary of significant accounting policies (Details) [Line Items]        
Concentration Risk, Percentage 23.00%      
Number Of Payers 2      
Clinical Labs [Member]        
Summary of significant accounting policies (Details) [Line Items]        
Receivable Percentage 74.00% 75.00%    
Clinical Labs [Member] | United Health Care of New York [Member]        
Summary of significant accounting policies (Details) [Line Items]        
Sales Revenue Services Net Percentage 39.00% 39.00% 30.00%  
Life Sciences [Member]        
Summary of significant accounting policies (Details) [Line Items]        
Royalties Receivable $ 0 $ 400,000