Concentrations of credit risk - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2017	Jul. 31, 2016
Concentration Risk [Line Items]
Cash, FDIC insured amount	$ 4.6		$ 4.6
Sales Revenue, Goods, Net | Customer One [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	22.00%	16.00%	18.00%	15.00%
Sales Revenue, Goods, Net | Customer Two [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	11.00%		13.00%
Accounts Receivable | Customer One [Member]
Concentration Risk [Line Items]
Concentration risk, percentage			26.00%
Accounts Receivable | Customer Two [Member]
Concentration Risk [Line Items]
Concentration risk, percentage			10.00%