Annual report pursuant to Section 13 and 15(d)

Stockholders' equity (Details)

v3.20.2
Stockholders' equity (Details) - USD ($)
$ / shares in Units, $ in Thousands
12 Months Ended
Jan. 05, 2018
Sep. 15, 2017
Jul. 31, 2020
Jul. 31, 2019
Jul. 31, 2018
Sep. 01, 2017
Dec. 31, 2014
Jan. 31, 2011
Stockholders' equity (Details) [Line Items]                
Common stock, par or stated value per share (in Dollars per share)     $ 0.01 $ 0.01        
Percentage of commission payable on equity offering     3.00%          
Maximum offering price under sales agreement     $ 20,000       $ 20,000  
Share-based compensation arrangement by share-based payment award, options, exercises in period (in Shares)     238,230 635,624      
Payments of stock issuance costs     $ 782 $ 832 $ 839      
Share-based compensation arrangement by share-based payment award, options, vested in period, fair value     0 159 743      
Share-based compensation arrangement by share-based payment award, options, outstanding, intrinsic value     79 955 1,723      
Share-based compensation arrangement by share-based payment award, options, exercises in period, intrinsic value     $ 0 $ 117 $ 6,014      
Performance share, description     one former executive forfeited a total of 14,500 PSUs.          
Minimum [Member]                
Stockholders' equity (Details) [Line Items]                
Share-based compensation arrangement by share-based payment award, award vesting period     2 years 2 years 2 years      
Maximum [Member]                
Stockholders' equity (Details) [Line Items]                
Share-based compensation arrangement by share-based payment award, award vesting period     3 years 3 years 3 years      
Performance Shares [Member]                
Stockholders' equity (Details) [Line Items]                
Share-based compensation arrangement by share-based payment award, award vesting period     3 years          
Restricted Stock Awards [Member]                
Stockholders' equity (Details) [Line Items]                
unvested restricted stock (in Shares)     817          
weighted average award price (in Dollars per share)     $ 3.34          
Unrecognized compensation cost     $ 3          
Restricted stock awards vested (in Shares)     811          
2011 Plan [Member]                
Stockholders' equity (Details) [Line Items]                
Share based compensation arrangement by share based payment award restricted stock units (in Shares)               3,000,000
Share-based compensation arrangement by share-based payment award, number of additional shares authorized (in Shares) 2,000,000              
Share-based compensation arrangement by share-based payment award, number of shares available for grant (in Shares) 5,000,000   937,000          
2011 Plan [Member] | Minimum [Member]                
Stockholders' equity (Details) [Line Items]                
Share-based compensation arrangement by share-based payment award, award vesting period     2 years          
2011 Plan [Member] | Maximum [Member]                
Stockholders' equity (Details) [Line Items]                
Share-based compensation arrangement by share-based payment award, award vesting period     4 years          
Common Stock [Member]                
Stockholders' equity (Details) [Line Items]                
Authorized common stock that may be issued and sold under sales agreement           $ 19,200    
Securities that may be sold under the agreement   $ 150,000            
Share-based compensation arrangement by share-based payment award, options, exercises in period (in Shares)       34,719 294,726      
Treasury stock, shares, acquired (in Shares)         340,898      
Stock issued during period, shares, employee compensation plan (in Shares)     333,265 315,472 37,580      
Payments of stock issuance costs     $ 839 $ 832 $ 782      
Stock issued during period shares of employee compensation (in Shares)     4,167          
Employee compensation expenses     $ 10          
Stock issued during period shares stock options exercised (in Shares)       23,376        
Common Stock [Member] | Restricted Stock Awards [Member]                
Stockholders' equity (Details) [Line Items]                
Share-based compensation arrangement by share-based payment award, options, vested in period, fair value     $ 2 $ 4 $ 24      
Treasury Stock [Member]                
Stockholders' equity (Details) [Line Items]                
Share-based compensation arrangement by share-based payment award, options, exercises in period (in Shares)            
Treasury stock, shares, acquired (in Shares)         106,911      
Treasury stock, value         $ 1,014      
Stock issued during period, shares, employee compensation plan (in Shares)     (106,911)      
Stock issued during period, shares, treasury stock reissued (in Shares)         106,911      
Stock issued during period shares stock options exercised (in Shares)              
Officer [Member] | Treasury Stock [Member]                
Stockholders' equity (Details) [Line Items]                
Share-based compensation arrangement by share-based payment award, options, exercises in period (in Shares)         340,898      
Directors And Officers [Member]                
Stockholders' equity (Details) [Line Items]                
Share-based compensation arrangement by share-based payment award, options, exercises in period (in Shares)       203,511        
Stock issued during period shares stock options exercised (in Shares)       23,376