Annual report pursuant to Section 13 and 15(d)

Summary of significant accounting policies (Details)

v3.19.3
Summary of significant accounting policies (Details)
12 Months Ended
Jul. 31, 2019
USD ($)
shares
Jul. 31, 2018
USD ($)
shares
Jul. 31, 2017
USD ($)
shares
Summary of significant accounting policies (Details) [Line Items]      
Number of Operating Segments 3    
Cash and Cash Equivalents, at Carrying Value $ 60,146,000 $ 60,041,000 $ 64,167,000
Contractual Adjustment Percentage 88.00% 85.00% 84.00%
Finite-Lived Intangible Asset, Useful Life 10 years    
Impairment of Long-Lived Assets Held-for-use $ 0 $ 0 $ 0
Advertising Expense $ 374,000 580,000 649,000
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements (in Shares) | shares 125,000    
Share-based Payment Arrangement, Noncash Expense $ 939,000 813,000 831,000
Excess Tax Benefit from Share-based Compensation, Operating Activities 0 $ 0 $ 0
Share-based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount $ 986,000    
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition 18 months    
New Accounting Pronouncement Or Change In Accounting Principle Expected Lease Liabilities $ 25,000,000    
New Accounting Pronouncement Or Change In Accounting Principle Expected Right of Use Assets $ 25,000,000    
Minimum [Member]      
Summary of significant accounting policies (Details) [Line Items]      
Finite-Lived Intangible Asset, Useful Life 4 years    
Maximum [Member]      
Summary of significant accounting policies (Details) [Line Items]      
Finite-Lived Intangible Asset, Useful Life 15 years    
Clinical Services [Member] | Revenue Benchmark [Member]      
Summary of significant accounting policies (Details) [Line Items]      
Concentration Risk, Percentage 63.00% 71.00% 71.00%
Clinical Laboratory Services [Member]      
Summary of significant accounting policies (Details) [Line Items]      
Receivable Percentage 63.00% 74.00%  
Building and Building Improvements [Member] | Minimum [Member]      
Summary of significant accounting policies (Details) [Line Items]      
Property, Plant and Equipment, Useful Life 15 years    
Building and Building Improvements [Member] | Maximum [Member]      
Summary of significant accounting policies (Details) [Line Items]      
Property, Plant and Equipment, Useful Life 30 years    
Machinery and Equipment [Member] | Minimum [Member]      
Summary of significant accounting policies (Details) [Line Items]      
Property, Plant and Equipment, Useful Life 3 years    
Machinery and Equipment [Member] | Maximum [Member]      
Summary of significant accounting policies (Details) [Line Items]      
Property, Plant and Equipment, Useful Life 10 years    
Third-Party Payers And Health Maintenance Organizations [Member] | Clinical Services [Member] | Revenue Benchmark [Member]      
Summary of significant accounting policies (Details) [Line Items]      
Concentration Risk, Percentage 36.00% 39.00% 39.00%
Foreign Bank [Member]      
Summary of significant accounting policies (Details) [Line Items]      
Cash and Cash Equivalents, at Carrying Value $ 700,000 $ 400,000  
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     0