Annual report pursuant to Section 13 and 15(d)

Segment reporting (Details) - Geographic financial information

v3.5.0.2
Segment reporting (Details) - Geographic financial information - USD ($)
$ in Thousands
 12 Months Ended
Jul. 31, 2016
Jul. 31, 2015
Jul. 31, 2014
Revenues from External Customers and Long-Lived Assets [Line Items]      
Net sales to unaffiliated customers $ 102,773 $ 97,599 $ 95,947
Long-lived assets at July 31,      
Long-lived assets 20,088 21,555  
UNITED STATES      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Net sales to unaffiliated customers 94,016 87,875 84,389
Long-lived assets at July 31,      
Long-lived assets 18,730 19,799  
SWITZERLAND      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Net sales to unaffiliated customers 2,709 3,131 4,130
Long-lived assets at July 31,      
Long-lived assets 917 1,224  
UNITED KINGDOM      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Net sales to unaffiliated customers 1,730 1,904 2,023
Long-lived assets at July 31,      
Long-lived assets 244 357  
Other International Countries [Member]      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Net sales to unaffiliated customers 4,318 4,689 $ 5,405
Long-lived assets at July 31,      
Long-lived assets $ 197 $ 175