v3.20.1

Income taxes - Narrative (Details) - USD ($) | 12 Months Ended
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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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- Definition Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32559-109319 + Details
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