Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss)
Beginning balance	$ 85,580	$ 42,069	$ 69,134
Net other comprehensive (loss) income	(95,454)	68,570	(42,184)
Ending balance	2,780	85,580	42,069
Foreign currency translation adjustment
Accumulated Other Comprehensive Income (Loss)
Beginning balance	(23,202)	(23,336)	(22,312)
Net other comprehensive (loss) income	(419)	134	(1,024)
Ending balance	(23,621)	(23,202)	(23,336)
Unrealized gain (loss) on marketable securities, net
Accumulated Other Comprehensive Income (Loss)
Beginning balance	(64)	(229)	(345)
Net other comprehensive (loss) income	269	165	116
Ending balance	205	(64)	(229)
Accumulated other comprehensive loss
Accumulated Other Comprehensive Income (Loss)
Beginning balance	(23,266)	(23,565)	(22,657)
Ending balance	$ (23,416)	$ (23,266)	$ (23,565)