Summary of Significant Accounting Policies - Components of Other Non-Operating Income (Expense) Recognized in Condensed Consolidated Financial Statements (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Nonoperating Income Expense [Abstract]
Interest Income	$ 801	$ 151	$ 2,515	$ 292
Foreign currency losses, net	(68)	(303)	(390)	(1,032)
Gain on sale of a private company investment	0	0	1,001	999
Other income (expense), net	154	(67)	315	(127)
Other non-operating income (expense), net	$ 887	$ (219)	$ 3,441	$ 132