Concentrations of credit risk - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Jan. 31, 2018	Jan. 31, 2017
Concentration Risk [Line Items]
Cash, FDIC insured amount	$ 5.3
Sales Revenue, Goods, Net
Concentration Risk [Line Items]
Concentration risk, percentage	36.00%
Sales Revenue, Goods, Net | Customer One [Member]
Concentration Risk [Line Items]
Concentration risk, percentage		15.00%
Sales Revenue, Goods, Net | Customer Two [Member]
Concentration Risk [Line Items]
Concentration risk, percentage		10.00%
Accounts Receivable
Concentration Risk [Line Items]
Concentration risk, percentage	32.00%
Accounts Receivable | Customer One [Member]
Concentration Risk [Line Items]
Concentration risk, percentage		15.00%
Accounts Receivable | Customer Two [Member]
Concentration Risk [Line Items]
Concentration risk, percentage		13.00%