Share Based Compensation - Outstanding stock options (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
Jan. 31, 2015
Number of options
Outstanding, beginning of period (in shares)	946,133
Granted (in shares)	194,900
Exercised (in shares)	(106,383)
Forfeited (in shares)	(14,750)
Expired (in shares)	(4,625)
Outstanding, end of period (in shares)	1,015,275
Weighted average exercise price
Outstanding, beginning of period (in usd per share)	$ 26.88
Granted (in usd per share)	$ 32.75
Exercised (in usd per share)	$ 16.24
Forfeited (in usd per share)	$ 31.24
Expired (in usd per share)	$ 31.10
Outstanding, end of period (in usd per share)	$ 29.04
Aggregate intrinsic value, Outstanding, end of period	$ 298
Weighted average remaining contractual term (years), Outstanding, end of period	2 years 3 months 27 days
Number of options, Outstanding exercisable, end of period	557,600
Weighted average exercise price, Outstanding exercisable, end of period	$ 26.40
Aggregate intrinsic value, Outstanding exercisable, end of period	$ 298
Weighted average remaining contractual term (years), Outstanding exercisable, end of period	1 year 5 months 45 days

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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Number of options or other stock instruments for which the right to exercise has lapsed under the terms of the plan agreements.

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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.

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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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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 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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Amount by which the current fair value of the underlying stock exceeds the exercise price of fully vested and expected to vest options outstanding.

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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 could have acquired the underlying shares with respect to stock options of the plan that expired.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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

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