Stock-Based Compensation - Summary of Stock Option and Other Equity Award Activity Under Plans (Details)	3 Months Ended
Mar. 31, 2019 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares Subject to Outstanding Options, Beginning Balance \| shares	3,701,461
Shares Subject to Outstanding Options, granted \| shares	1,080,413
Shares Subject to Outstanding Options, exercised \| shares	(19,596)
Shares Subject to Outstanding Options, canceled \| shares	(49,527)
Shares Subject to Outstanding Options, Ending Balance \| shares	4,712,751
Weighted Average Exercise Price per Share, Beginning Balance \| $ / shares	$ 26.40
Weighted Average Exercise Price Per Share, granted \| $ / shares	40.68
Weighted Average Exercise Price per Share, exercised \| $ / shares	14.30
Weighted Average Exercise Price Per Share, forfeited \| $ / shares	25.86
Weighted Average Exercise Price Per Share, Ending Balance \| $ / shares	$ 29.73
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares Subject to Outstanding Awards, Beginning Balance \| shares	162,946
Shares Subject to Outstanding Awards, RSUs awarded \| shares	412,499
Shares Subject to Outstanding Awards, RSUs released \| shares	(26,230)
Shares Subject to Outstanding Awards, RSUs forfeited \| shares	(4,826)
Shares Subject to Outstanding Awards, Ending Balance \| shares	544,389
Weighted Average Grant Date Fair Value. Beginning Balance \| $ / shares	$ 53.37
Weighted Average Grant Date Fair Value. RSUs awarded \| $ / shares	40.78
Weighted Average Grant Date Fair Value. RSUs released \| $ / shares	52.85
Weighted Average Grant Date Fair Value. RSUs forfeited \| $ / shares	47.08
Weighted Average Grant Date Fair Value. Ending Balance \| $ / shares	$ 43.91

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

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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.

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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).

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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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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.

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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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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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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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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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No definition available.

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Number of options outstanding, including both vested and non-vested options.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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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 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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No definition available.

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

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