Stock-Based Compensation - Summary of Stock Option and Other Equity Award Activity Under Plans (Details)	6 Months Ended
Jun. 30, 2018 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares Subject to Outstanding Options, Beginning Balance \| shares	2,964,549
Shares Subject to Outstanding Options, granted \| shares	1,167,256
Shares Subject to Outstanding Options, exercised \| shares	(263,145)
Shares Subject to Outstanding Options, canceled \| shares	(99,248)
Shares Subject to Outstanding Options, Ending Balance \| shares	3,769,412
Weighted Average Exercise Price per Share, Beginning Balance \| $ / shares	$ 11.54
Weighted Average Exercise Price Per Share, granted \| $ / shares	51.41
Weighted Average Exercise Price per Share, exercised \| $ / shares	7.31
Weighted Average Exercise Price Per Share, forfeited \| $ / shares	20.26
Weighted Average Exercise Price Per Share, Ending Balance \| $ / shares	$ 23.95
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares Subject to Outstanding Awards, granted \| shares	138,086
Shares Subject to Outstanding Awards, forfeited \| shares	(2,830)
Shares Subject to Outstanding Awards, Ending Balance \| shares	135,256
Weighted Average Grant Date Fair Value, granted \| $ / shares	$ 51.88
Weighted Average Grant Date Fair Value, forfeited \| $ / shares	53.77
Weighted Average Grant Date Fair Value. Ending Balance \| $ / shares	$ 51.84

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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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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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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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 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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