Stock-based Compensation - Stock Option Activities (Detail) $ / shares in Units, $ in Thousands	6 Months Ended
Jul. 31, 2018 USD ($) $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares, Outstanding \| shares	1,611,344
Shares, Granted \| shares	60,050
Shares, Exercised \| shares	(195,179)
Shares, Forfeited \| shares	(12,026)
Shares, Expired \| shares	(6,637)
Shares, Outstanding \| shares	1,457,552
Shares, Exercisable \| shares	1,234,750
Weighted-Average Exercise Price, Outstanding	$ 24.56
Weighted-Average Exercise Price, Granted	45.74
Weighted-Average Exercise Price, Exercised	4.85
Weighted-Average Exercise Price, Forfeited	53.92
Weighted-Average Exercise Price, Expired	44.39
Weighted-Average Exercise Price, Outstanding	27.74
Weighted-Average Exercise Price, Exercisable	23.17
Weighted-Average Grant-date Fair Value, Granted	$ 23.43
Total Intrinsic Value Of Options Exercised \| $	$ 7,838
Weighted-Average Remaining Contractual Term, Outstanding	4 years 9 months 21 days
Weighted-Average Remaining Contractual Term, Exercisable	4 years 1 month 17 days
Aggregate Intrinsic Value, Outstanding \| $	$ 24,385
Aggregate Intrinsic Value, Exercisable \| $	$ 24,377

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

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