Stock Plans and Stock-Based Compensation - Schedule of Stock Option Activity (Details) - $ / shares	9 Months Ended	12 Months Ended
Sep. 30, 2018	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock options outstanding, Beginning Balance	2,440,290	1,884,425
Stock options outstanding, Granted	557,896	1,096,881
Stock options outstanding, Exercised	(703,826)	(497,175)
Stock options outstanding, Forfeited	(457,689)	(43,841)
Stock options outstanding, Ending Balance	1,836,671	2,440,290
Weighted average exercise price, Beginning Balance	$ 16.55	$ 10.02
Weighted average exercise price, Granted	35.01	22.84
Weighted average exercise price, Exercised	12.53	5.77
Weighted average exercise price, Forfeited	22.38	15.60
Weighted average exercise price, Ending Balance	$ 22.24	$ 16.55

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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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