Summary of Significant Accounting Policies - Components of Accumulated Other Comprehensive Income (Loss), Net of Tax (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
AOCI Attributable to Parent, Net of Tax
Beginning balance	$ (5,418)	$ 51,814	$ 54,957
Ending balance	8,397	(5,418)	51,814
Foreign currency translation adjustment
AOCI Attributable to Parent, Net of Tax
Beginning balance	(4,557)	(4,404)	(4,482)
Other comprehensive income during the year	34	(153)	78
Ending balance	(4,523)	(4,557)	(4,404)
Unrealized gains (losses) on marketable securities
AOCI Attributable to Parent, Net of Tax
Beginning balance	0	(16)	(36)
Other comprehensive income during the year	0	16	20
Ending balance	0	0	(16)
Accumulated other comprehensive income (loss)
AOCI Attributable to Parent, Net of Tax
Beginning balance	(4,557)	(4,420)	(4,518)
Other comprehensive income during the year	34	(137)	98
Ending balance	$ (4,523)	$ (4,557)	$ (4,420)