Stock-Based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2020	Dec. 31, 2019
Number of Shares
Number of shares outstanding, beginning of period (in shares)	12,939
Number of shares, granted (in shares)	0
Number of shares, exercised (in shares)	(635)
Number of shares, forfeited/canceled (in shares)	(190)
Number of shares outstanding, end of period (in shares)	12,114	12,939
Number of shares exercisable (in shares)	6,783
Weighted Average Exercise Price
Weighted average exercise price, outstanding, beginning of period (in usd per share)	$ 8.38
Weighted average exercise price, granted (in usd per share)	0
Weighted average exercise price, exercised (in usd per share)	6.27
Weighted average exercise price, forfeited/canceled (in usd per share)	10.78
Weighted average exercise price, outstanding, end of period (in usd per share)	8.45	$ 8.38
Weighted average exercise price, exercisable (in usd per share)	$ 6.12
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted average remaining contractual term (in years), outstanding	7 years	7 years 1 month 6 days
Weighted average remaining contractual term (in years), exercisable	6 years 6 months
Aggregate intrinsic value, outstanding	$ 162,596	$ 201,608
Aggregate intrinsic value, exercised	12,383
Aggregate intrinsic value, exercisable	$ 106,847

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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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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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

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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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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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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