Stock-based compensation (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	6 Months Ended	12 Months Ended
Jul. 31, 2012	Jan. 31, 2012
unvested option [Member]
Option activity [Line Items]
Outstanding on February 1, 2012	380	373
Weighted Average Exercise Price Per Share	$ 6.98	$ 7.84
Options Outstanding Aggregate Intrinsic Value	$ 89	$ 212
Granted	158
Granted Weighted Average Exercise Price Per Share	$ 6.88
Vested options in the period	(142)
Expired or forfeited	9
Expired or Forfeited Weighted Average Exercise Price Per Share	$ 7.08
Stock Option [Member]
Option activity [Line Items]
Outstanding on February 1, 2012		843
Weighted Average Exercise Price Per Share		$ 11.48
Weighted Average Remaining Contractual Term		6 years 10 months 24 days
Options Outstanding Aggregate Intrinsic Value	225	430
Granted	158
Exercised	(11)
Exercised Weighted Average Exercise Price Per Share	$ 2.94
Exercised Aggregate Intrinsic Value	45
Expired or forfeited	(26)
Expired or Forfeited Weighted Average Exercise Price Per Share	$ 10.25
Outstanding end of period	964
Outstanding Weighted Average Exercise Price Per Share	$ 10.85
Outstanding Weighted Average Remaining Contractual Term	7 years
Exercisable end of period	584
Exercisable Weighted Average Remaining Contractual Term	5 years 9 months 18 days
Exercisable Weighted Average Exercise Price Per Share	$ 13.37
Exercisable Aggregate Intrinsic Value	$ 137
Weighted-average fair value of options granted during first six months of 2012	$ 3.37

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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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The total accumulated difference between fair values of underlying shares on dates of exercise and exercise price on options which were exercised (or share units converted) into shares during the reporting period under the plan.

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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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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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

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The number of shares reserved for issuance under stock option agreements awarded under the plan that validly exist and are outstanding as of the balance sheet date, including 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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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average price at which grantees can acquire the shares reserved for issuance on stock options awarded.

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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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