Stock-Based Compensation - Schedule of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
AOCI Attributable to Parent [Roll Forward]
Beginning balance			$ 105,665
Net other comprehensive income (loss), September 30, 2017	$ (751)	$ 1,977	(2,135)	$ 5,060
Ending balance	101,730		101,730
Foreign Currency Translation
AOCI Attributable to Parent [Roll Forward]
Beginning balance	(12,669)	(13,610)	(11,247)	(16,651)
Other comprehensive income (loss) before reclassifications	(763)	1,956	(2,185)	4,997
Amounts reclassified from AOCI to Other income (expense), net	0	0	0	0
Net other comprehensive income (loss), September 30, 2017	(763)	1,956	(2,185)	4,997
Ending balance	(13,432)	(11,654)	(13,432)	(11,654)
Unrealized Gain (Loss) on Available for Sale Marketable Securities
AOCI Attributable to Parent [Roll Forward]
Beginning balance	0	(3)	(1)	0
Other comprehensive income (loss) before reclassifications	0	2	1	(1)
Amounts reclassified from AOCI to Other income (expense), net	0	0	0	0
Net other comprehensive income (loss), September 30, 2017	0	2	1	(1)
Ending balance	0	(1)	0	(1)
Unrealized Gain (Loss) on Available for Sale Marketable Securities
AOCI Attributable to Parent [Roll Forward]
Beginning balance	(32)	(113)	(69)	(158)
Other comprehensive income (loss) before reclassifications	0	1	11	5
Amounts reclassified from AOCI to Other income (expense), net	12	18	38	59
Net other comprehensive income (loss), September 30, 2017	12	19	49	64
Ending balance	(20)	(94)	(20)	(94)
Total Accumulated Other Comprehensive Loss
AOCI Attributable to Parent [Roll Forward]
Beginning balance	(12,701)	(13,726)	(11,317)	(16,809)
Other comprehensive income (loss) before reclassifications	(763)	1,959	(2,173)	5,001
Amounts reclassified from AOCI to Other income (expense), net	12	18	38	59
Net other comprehensive income (loss), September 30, 2017	(751)	1,977	(2,135)	5,060
Ending balance	$ (13,452)	$ (11,749)	$ (13,452)	$ (11,749)