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Intangible assets - Additional Information (Detail) - USD ($)
6 Months Ended 12 Months Ended
Apr. 30, 2018
Oct. 31, 2017
Intangible Assets [Line Items]    
Amortization expense $ 277,000 $ 589,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life 9 years 5 months 23 days