Stock-based compensation (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	6 Months Ended	12 Months Ended
Jul. 31, 2013	Jan. 31, 2013
unvested option [Member]
Option activity [Line Items]
Outstanding at beginning of year	279	383
Weighted Average Exercise Price Per Share	$ 8.14	$ 6.91
Options Outstanding Aggregate Intrinsic Value	$ 753	$ 4
Granted Weighted average exercise price	$ 10.46
Vested	(176)
Expired or forfeited	(25)
Expired or Forfeited Weighted Average Exercise Price Per Share	$ 6.96
Stock Option [Member]
Option activity [Line Items]
Outstanding at beginning of year		969
Weighted Average Exercise Price Per Share		$ 10.77
Weighted Average Remaining Contractual Term		6 years 7 months 24 days
Options Outstanding Aggregate Intrinsic Value	2,325	40
Granted	97
Exercised	(74)
Exercised Weighted Average Exercise Price Per Share	$ 6.33
Exercised Aggregate Intrinsic Value	265
Expired or forfeited	(43)
Expired or Forfeited Weighted Average Exercise Price Per Share	$ 11.11
Outstanding end of period	949
Outstanding Weighted Average Exercise Price Per Share	$ 11.07
Outstanding Weighted Average Remaining Contractual Term	6 years 6 months
Exercisable end of period	670
Exercisable Weighted Average Remaining Contractual Term	5 years 6 months
Exercisable Weighted Average Exercise Price Per Share	$ 12.29
Exercisable Aggregate Intrinsic Value	$ 1,572

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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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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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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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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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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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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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

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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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Weighted average remaining contractual term for fully vested and expected to vest options that are 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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As of the balance sheet date, the number of shares into which fully vested and expected to vest stock options outstanding can be converted under the option plan.

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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 the reported fact of one year, five months, and thirteen days.

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Number of options vested.

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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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The weighted average price as of the balance sheet date at which grantees could acquire the underlying shares with respect to all outstanding stock options which are in the customized range of exercise prices.

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

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