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Concentrations of credit risk - Additional Information (Detail) - USD ($)
3 Months Ended 9 Months Ended 12 Months Ended
Jul. 31, 2015
Jul. 31, 2014
Jul. 31, 2015
Jul. 31, 2014
Oct. 31, 2014
Concentration Risk [Line Items]          
Cash, FDIC insured amount $ 6,700,000   $ 6,700,000    
Concentration risk, percentage   7.00%   11.00%  
Concentration agreement with major customer     15 years    
Sales revenue, goods, net   $ 388,000   $ 1,800,000  
Sales Revenue, Goods, Net          
Concentration Risk [Line Items]          
Concentration risk, percentage 16.00% 34.00% 18.00% 33.00%  
Accounts Receivable          
Concentration Risk [Line Items]          
Concentration risk, percentage     28.00%   34.00%