Annual report pursuant to Section 13 and 15(d)

Segment reporting (Details) - Geographic financial information

v3.7.0.1
Segment reporting (Details) - Geographic financial information - USD ($)
$ in Thousands
 12 Months Ended
Jul. 31, 2017
Jul. 31, 2016
Jul. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]      
Net sales to unaffiliated customers $ 107,804 $ 102,773 $ 97,599
Long-lived assets 18,248 20,088  
UNITED STATES      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Net sales to unaffiliated customers 99,469 94,016 87,875
Long-lived assets 17,241 18,730  
SWITZERLAND      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Net sales to unaffiliated customers 2,371 2,709 3,131
Long-lived assets 649 917  
UNITED KINGDOM      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Net sales to unaffiliated customers 1,673 1,730 1,904
Long-lived assets 185 244  
Other International Countries [Member]      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Net sales to unaffiliated customers 4,291 4,318 $ 4,689
Long-lived assets $ 173 $ 197