Stock Incentive Plans - PSO and Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	6 Months Ended
Jun. 30, 2020
Performance stock options ("PSOs")
Number of Shares Outstanding, beginning balances	6,583
Number of Shares Outstanding, Canceled	(1,377)
Number of Shares Outstanding, Exercised	(948)
Number of Shares Outstanding, ending balances	4,258
Number of Shares Outstanding, expected to vest	526
Number of Shares Outstanding, exercisable	2,800
Weighted Average Exercise Price, beginning balance	$ 4.54
Weighted Average Exercise Price, Canceled	6.18
Weighted Average Exercise Price, Exercised	3.61
Weighted Average Exercise Price, ending balance	4.21
Weighted Average Exercise Price, expected to vest	3.60
Weighted Average Exercise Price, exercisable	$ 3.59
Weighted Average Remaining Contractual Term, ending balance	7 years 6 months 10 days
Weighted Average Remaining Contractual Term, expected to vest	7 years 4 months 6 days
Weighted Average Remaining Contractual Term, exercisable	7 years 3 months 18 days
Aggregate Intrinsic Value, ending balance	$ 21,531
Aggregate Intrinsic Value, expected to vest	2,984
Aggregate Intrinsic Value, exercisable	$ 15,892
Stock Options
Number of Shares Outstanding, beginning balances	16,288
Options granted, number of shares	210
Number of Shares Outstanding, Canceled	(287)
Number of Shares Outstanding, Exercised	(3,460)
Number of Shares Outstanding, ending balances	12,751
Number of Shares Outstanding, exercisable	8,619
Weighted Average Exercise Price, beginning balance	$ 3.56
Options granted, weighted average exercise price	9.00
Weighted Average Exercise Price, Canceled	5.35
Weighted Average Exercise Price, Exercised	3.36
Weighted Average Exercise Price, ending balance	3.66
Weighted Average Exercise Price, exercisable	$ 3.28
Weighted Average Remaining Contractual Term, ending balance	6 years 11 months 23 days
Weighted Average Remaining Contractual Term, exercisable	6 years 8 months 15 days
Aggregate Intrinsic Value, ending balance	$ 71,487
Aggregate Intrinsic Value, exercisable	$ 51,668

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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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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Net 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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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Amount by which current fair value of underlying stock exceeds exercise price of fully vested and expected to vest options outstanding. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Number of fully vested and expected to vest options outstanding that can be converted into shares under option plan. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted-average exercise price, at which grantee can acquire shares reserved for issuance, for fully vested and expected to vest options outstanding. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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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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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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Weighted average remaining contractual term for fully vested and expected to vest options outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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

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