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Stock-based Compensation - Employee Stock Purchase Plan (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	May 31, 2017	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	May 18, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from issuance of common stock, net of offering costs		$ 170,456	$ 118,657	$ 103,259
2016 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, number of shares authorized (in shares)					800,000
Maximum employee contribution percent	10.00%
Percent of fair market value to purchase shares	85.00%
Common stock purchased by employees (in shares)		32,430
Proceeds from issuance of common stock, net of offering costs		$ 600

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