Share Based Compensation - Outstanding stock options (Details) $ / shares in Units, $ in Thousands	12 Months Ended
Jan. 31, 2020 USD ($) $ / shares shares
Number of options
Outstanding, beginning of period (in shares) \| shares	368,130
Granted (in shares) \| shares	0
Exercised (in shares) \| shares	(146,145)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period \| shares	7,725
Outstanding, end of period (in shares) \| shares	214,260
Weighted average exercise price
Outstanding, beginning of period (in usd per share) \| $ / shares	$ 23.06
Granted (in usd per share) \| $ / shares	0
Exercised (in usd per share) \| $ / shares	20.30
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period, Weighted Average Exercise Price \| $ / shares	20.62
Outstanding, end of period (in usd per share) \| $ / shares	$ 25.03
Aggregate intrinsic value, Outstanding, end of period \| $	$ 1,564
Weighted average remaining contractual term (years), Outstanding, end of period	2 years
Number of options, outstanding exercisable, end of period \| shares	76,879
Share-based compensation arrangement by share-based payment award, options, vested and expected to vest, outstanding, number \| shares	214,260
Weighted average exercise price, Outstanding exercisable, end of period \| $ / shares	$ 24.18
Share-based compensation arrangement by share-based payment award, options, vested and expected to vest, outstanding, weighted average exercise price \| $ / shares	$ 25.03
Aggregate intrinsic value, Outstanding exercisable, end of period \| $	$ 603
Weighted average remaining contractual term (years), Outstanding exercisable, end of period	1 year 10 months 6 days
Share-based compensation arrangement by share-based payment award, options, vested and expected to Vest, outstanding, weighted average remaining contractual term	2 years
Share-based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount \| $	$ 265

Amount of cost to be recognized for option under share-based payment arrangement.

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- Definition

The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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- Definition

For presentations that combine terminations, the number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan or that expired.

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Weighted average price of options that were either forfeited or expired.

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Net number of share options (or share units) granted during the period.

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Number of options outstanding, including both vested and non-vested options.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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No definition available.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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- Definition

Amount by which current fair value of underlying stock exceeds exercise price of fully vested and expected to vest options outstanding. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Number of fully vested and expected to vest options outstanding that can be converted into shares under option plan. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted-average exercise price, at which grantee can acquire shares reserved for issuance, for fully vested and expected to vest options outstanding. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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- Definition

Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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- Definition

Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average remaining contractual term for fully vested and expected to vest options outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Number of share options (or share units) exercised during the current period.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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-SubTopic 10
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