Summary of Significant Accounting Policies - Components of Other Non-Operating (Income) Expense Recognized in Condensed Consolidated Financial Statements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Nonoperating Income Expense [Abstract]
Interest Income	$ (780)	$ (3,030)	$ (1,161)
Foreign currency (gains) losses, net	225	399	1,460
Gain on sale of a private company investment	(1,001)	(1,001)	(999)	$ (6,800)
Loss on debt modification / extinguishment	0	0	941
Other (income) expense, net	120	(330)	57
Other non-operating (income) expense, net	$ (1,436)	$ (3,962)	$ 298