v3.20.1

Income taxes - Narrative (Details) - USD ($)	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Operating Loss Carryforwards [Line Items]
Effective income tax rate	8.10%	2.50%	9.20%
Current statutory rate differential due to tax reform	$ 0	$ 0	$ 308,000
Deferred tax asset, valuation allowance	203,000	97,000
Total gross unrecognized tax benefits	9,370,000	1,693,000	$ 889,000
Anticipated decrease in total gross unrecognized tax benefits within 12 months	8,600,000	1,500,000
Period increase (decrease) in unrecognized tax benefit	7,700,000
Unrecognized tax benefits, income tax penalties and interest expense	100,000	0
Unrecognized tax benefits, income tax penalties and interest accrued	600,000	0
Accrued interest, increase resulting from acquisition	500,000
December 31, 2025 Through 2036 | State
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	20,500,000
December 31, 2019 | Research | Federal
Operating Loss Carryforwards [Line Items]
Credit carryforward	$ 3,600,000
December 31, 2024 | Research | State
Operating Loss Carryforwards [Line Items]
Credit carryforward		$ 7,800,000

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