Annual report pursuant to Section 13 and 15(d)

Income taxes (Details)

v3.7.0.1
Income taxes (Details) - USD ($)
$ in Thousands
 12 Months Ended
Jul. 31, 2017
Jul. 31, 2016
Income taxes (Details) [Line Items]    
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount $ 2,300 $ 14,700
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration 56,200  
Deferred Tax Assets Research and Development and Other Tax Credit Carryforwards 2,208 $ 2,152
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax 1,100  
Foreign Loss Carryforwards 9,300  
Undistributed Earnings of Foreign Subsidiaries 87  
Liability for Uncertain Tax Position 0  
U.S. Federal Tax [Member]    
Income taxes (Details) [Line Items]    
Deferred Tax Assets Research and Development and Other Tax Credit Carryforwards $ 1,100  
Minimum [Member] | Domestic Tax Authority [Member]    
Income taxes (Details) [Line Items]    
Operating Loss Carryforwards Expiration Year 2030  
Minimum [Member] | Research Tax Credit Carryforward [Member]    
Income taxes (Details) [Line Items]    
Tax Credit Carryforward Expiration Year 2025  
Maximum [Member] | Domestic Tax Authority [Member]    
Income taxes (Details) [Line Items]    
Operating Loss Carryforwards Expiration Year 2035  
Maximum [Member] | Research Tax Credit Carryforward [Member]    
Income taxes (Details) [Line Items]    
Tax Credit Carryforward Expiration Year 2037