Income taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2020	Oct. 31, 2019	Jan. 31, 2020
Income Tax Disclosure [Abstract]
Income tax expense	$ 2,340	$ (9,918)	$ 2,015	$ 3,908
Effective tax rate	56.70%	(31.70%)	36.80%	8.90%
Effective tax rate, primarily due to excess tax benefit on stock-based compensation expense (benefit)	6.00%	(1.10%)	(9.60%)	(8.70%)
Gross unrecognized tax benefits	$ 10,000		$ 10,000		$ 9,400
Unrecognized tax benefit	500		500		$ 500
Unrecognized tax benefits that would impact the effective tax rate	$ 9,200		$ 9,200