Stock Based Compensation - Summary of Unvested Stock Options (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Stock Based Compensation
Stock Options Outstanding - Beginning Balance	2,072	1,945
Stock Options Granted (in shares)	478	423
Stock option Exercised (in shares)	(46)	(119)
Stock Options Forfeited (in shares)	(13)	(168)
Stock Options Cancelled (in shares)		(9)
Stock Options Outstanding - Ending Balance	2,491	2,072	1,945
Options exercisable - Ending Balance	870
Weighted Average Exercise Price Outstanding - Beginning Balance	$ 24.63	$ 23.45
Weighted Average Exercise Price - Granted	19.49	27.54
Weighted Average Exercise Price - Exercised	21.65	19.51
Weighted Average Exercise Price - Forfeited	22.98	21.92
Weighted Average Exercise Price - Expired		25.70
Weighted Average Exercise Price Outstanding - Ending Balance	$ 23.70	$ 24.63	$ 23.45
Aggregate Intrinsic Value	$ 5,974	$ 6,266	$ 5,527
Weighted Average Remaining Contractual Life (years)	7 years 10 months 24 days	8 years	9 years 1 month 6 days

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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Number of options or other stock instruments for which the right to exercise has lapsed under the terms of the plan agreements.

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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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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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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 of the plan that expired.

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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 non-vested options outstanding.

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Weighted average grant-date fair value of non-vested options outstanding.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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

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