Stock-Based Compensation - Summary of Stock Option Activity (Details)	9 Months Ended
Sep. 30, 2018 $ / shares shares
Number of Shares
Balances at December 31, 2017 \| shares	4,196,203
Granted \| shares	1,724,893
Exercised \| shares	(404,597)
Canceled \| shares	(252,116)
Balances at September 30, 2018 \| shares	5,264,383
Weighted-Average Exercise Price
Balances at December 31, 2017 \| $ / shares	$ 3.06
Granted \| $ / shares	13.41
Exercised \| $ / shares	3.11
Canceled \| $ / shares	6.13
Balances at September 30, 2018 \| $ / shares	$ 6.30

For presentations that combine terminations, 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 or that expired.

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Weighted average price of options that were either forfeited or expired.

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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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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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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 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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