Comprehensive Income (Loss) - Components (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Accumulated Other Comprehensive Loss:
Beginning balance	$ (9,582)	$ 86,639	$ 2,780	$ 85,580
Net other comprehensive (loss) income	(8,250)	(3,842)	(21,055)	(16,067)
Ending balance	(17,777)	78,546	(17,777)	78,546
Foreign currency translation adjustment:
Accumulated Other Comprehensive Loss:
Beginning balance	(23,782)	(22,953)	(23,621)	(23,202)
Net other comprehensive (loss) income	62	(482)	(99)	(233)
Ending balance	(23,720)	(23,435)	(23,720)	(23,435)
Unrealized gain (loss) on marketable securities, net
Accumulated Other Comprehensive Loss:
Beginning balance	579	(302)	205	(64)
Net other comprehensive (loss) income	293	78	667	(160)
Ending balance	872	(224)	872	(224)
Accumulated Other Comprehensive Loss:
Accumulated Other Comprehensive Loss:
Beginning balance	(23,203)	(23,670)	(23,416)	(23,266)
Ending balance	$ (22,848)	$ (23,659)	$ (22,848)	$ (23,659)