Stock Plans and Stock-Based Compensation - Schedule of Stock Option Activity (Details) - $ / shares	3 Months Ended	12 Months Ended
Mar. 31, 2019	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock options outstanding, Beginning Balance	1,746,073	2,440,290
Stock options outstanding, Granted	0	557,896
Stock options outstanding, Exercised	(501,083)	(778,370)
Stock options outstanding, Forfeited	(18,084)	(473,743)
Stock options outstanding, Ending Balance	1,226,906	1,746,073
Weighted average exercise price, Beginning Balance	$ 22.43	$ 16.55
Weighted average exercise price, Granted		35.01
Weighted average exercise price, Exercised	17.46	13.04
Weighted average exercise price, Forfeited	31.08	22.35
Weighted average exercise price, Ending Balance	$ 24.34	$ 22.43

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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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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
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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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