Summary of significant accounting policies (Details) - USD ($) $ in Thousands	3 Months Ended
	Apr. 30, 2020		Feb. 01, 2020	Jan. 31, 2020	[1]
Concentration Risk [Line Items]
Lease right-of-use assets	$ 2,795	[1]	$ 2,741	$ 0
Operating lease liabilities	$ 2,992		$ 2,928
Largest Customer | Accounts Receivable | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk, percentage	15.00%
Second Largest Customer | Accounts Receivable | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk, percentage	10.00%

[1] (1) Figures as of April 30, 2020 reflect the Company's February 1, 2020 adoption of Accounting Standards Update ("ASU") No. 2016-02, Leases. For additional details, see Note 3(c), "Summary of significant accounting policies — Impact of recently adopted accounting pronouncements."