Stock-based Compensation - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation	$ 2,844	$ 1,939	$ 5,531	$ 4,108
Stock options
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation	682	575	1,347	1,116
Compensation not yet recognized, stock options	4,800		4,800
RSUs and RSAs
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation	690	610	1,232	1,210
Compensation not yet recognized, share-based awards other than options	4,700		4,700
PSUs
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation	573	296	1,043	627
Compensation not yet recognized, share-based awards other than options	1,900		1,900
PBOs
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation	899	458	1,909	1,155
Compensation not yet recognized, share-based awards other than options	3,300		3,300
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation	597	471	1,074	894
Selling, general and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation	$ 2,247	$ 1,468	$ 4,457	$ 3,214

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Amount of cost to be recognized for nonvested award under share-based payment arrangement. Excludes share and unit options.

+ References

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-Publisher FASB
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-Topic 718
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Amount of cost to be recognized for option under share-based payment arrangement.

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Amount of noncash expense for share-based payment arrangement.

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