Segment information - Sales by geographic area (Details) - USD ($) $ in Thousands	3 Months Ended
	Jan. 31, 2020	Jan. 31, 2019
Revenue, Major Customer [Line Items]
Sales revenue	$ 12,414	$ 10,647
United States
Revenue, Major Customer [Line Items]
Sales revenue	12,173	10,470
Foreign countries, total
Revenue, Major Customer [Line Items]
Sales revenue	241	177
Canada
Revenue, Major Customer [Line Items]
Sales revenue	116	165
Mexico
Revenue, Major Customer [Line Items]
Sales revenue	5	0
All other
Revenue, Major Customer [Line Items]
Sales revenue	$ 120	$ 12