Income taxes (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2020	Oct. 31, 2019
Income Tax Disclosure [Abstract]
Provision for income taxes	$ (194,000)	$ (64,000)	$ (371,000)	$ (183,000)
Effective tax rate			2.00%	1.10%