Revenue recognition - Additional Information (Detail) - USD ($)	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Disaggregation of Revenue [Line Items]
Capitalized contract cost, amortization period	3 years
Deferred contract acquisition cost amortization	$ 1,977,000	$ 1,640,000	$ 1,389,000
Capitalized contract cost, impairment loss	0	0	0
Subscription and related services
Disaggregation of Revenue [Line Items]
Revenues recorded pursuant to ASC 840	$ 5,985,000	$ 4,749,000	$ 3,544,000