Summary of Stock Option Activity (Detail) (Stock Options, USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
Jan. 31, 2015	Jan. 31, 2014
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards outstanding at beginning of year, Shares	2,813,194
Granted, Shares	100,000
Exercised, Shares	(422,187)
Forfeited or Expired, Shares	(26,617)
Awards outstanding at end of year, Shares	2,464,390	2,813,194
Awards outstanding expected to vest, Shares	2,458,921
Awards exercisable at end of year, Shares	2,355,015
Awards outstanding at beginning of year, Weighted Average Exercise Price	$ 31.55
Granted, Weighted Average Exercise Price	$ 35.85
Exercised, Weighted Average Exercise Price	$ 25.33
Forfeited or Expired, Weighted Average Exercise Price	$ 40.56
Awards outstanding at end of year, Weighted Average Exercise Price	$ 32.69	$ 31.55
Awards outstanding expected to vest, Weighted Average Exercise Price	$ 32.69
Awards exercisable at end of year, Weighted Average Exercise Price	$ 32.54
Awards outstanding at end of year, Weighted Average Remaining Contractual Term (years)	1 year 7 months 6 days	2 years 3 months 18 days
Awards outstanding expected to vest, Weighted Average Remaining Contractual Term (years)	1 year 7 months 6 days
Awards exercisable at end of year, Weighted Average Remaining Contractual Term (years)	1 year 7 months 6 days
Awards outstanding at beginning of year, Aggregate Intrinsic Value	$ 14,502
Awards outstanding at end of year, Aggregate Intrinsic Value	8,547	14,502
Awards outstanding expected to vest, Aggregate Intrinsic Value	8,120
Awards exercisable at end of year, Aggregate Intrinsic Value	$ 8,538

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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 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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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 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 of difference between fair value of the underlying shares reserved for issuance and exercise price of fully vested and expected to vest options that are exercisable.

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The number of exercisable share options (fully vested and expected to vest) that may be converted as of the balance sheet date.

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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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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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As of the balance sheet date, the weighted-average exercise price for outstanding stock options that are fully vested or expected to vest.

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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 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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