Stockholders' Equity - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 245,059	$ 522,801	$ 301,521
Amounts arising during the period	(457)	702	3
Reclassification adjustments	7	(326)
Ending balance	369,669	245,059	522,801
Net Unrealized Gains (Losses) on Marketable Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	379	3	0
Amounts arising during the period	(197)	702	3
Reclassification adjustments	7	(326)
Ending balance	189	379	3
Foreign Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	0	0	0
Amounts arising during the period	(260)	0	0
Reclassification adjustments	0	0
Ending balance	(260)	0	0
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	379	3	0
Ending balance	$ (71)	$ 379	$ 3