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Income tax provision - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended
Apr. 30, 2017
Apr. 30, 2016
Apr. 30, 2017
Apr. 30, 2016
Oct. 31, 2016
Income Taxes [Line Items]          
Provision for income tax as percentage of income (loss) before income taxes 47.00% (238.00%) 26.00% 60.00%  
Unrecognized tax benefits $ 0   $ 0   $ 0
Accrued interest and penalties related to uncertain tax positions $ 0   $ 0   $ 0