Stockholders' Equity - Summary of Restricted Stock Unit (RSU) Activity (Detail) - Restricted Stock Units (RSUs) [Member]	9 Months Ended
Oct. 31, 2018 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unreleased restricted stock units, Beginning Balance \| shares	2,901,736
Unreleased restricted stock units, RSUs granted \| shares	1,026,242
Unreleased restricted stock units, RSUs vested \| shares	(986,405)
Unreleased restricted stock units, RSUs forfeited/cancelled \| shares	(245,685)
Unreleased restricted stock units, Ending Balance \| shares	2,695,888
Weighted average grant date fair value, Beginning Balance \| $ / shares	$ 38.14
Weighted average grant date fair value, RSUs granted \| $ / shares	75.86
Weighted average grant date fair value, RSUs vested \| $ / shares	37.32
Weighted average grant date fair value, RSUs forfeited/cancelled \| $ / shares	44.67
Weighted average grant date fair value, Ending Balance \| $ / shares	$ 52.20

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(3)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

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- Definition

Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

+ References

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-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

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-Publisher FASB
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-Paragraph 2
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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ References

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-Publisher FASB
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- Definition

The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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-Publisher FASB
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- Definition

The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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