Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Increase (Decrease) in Accumulated Other Comprehensive Loss [Roll Forward]
Balance at beginning of period			$ 34,341
Balance at end of period	$ 33,301		33,301
Foreign currency translation
Increase (Decrease) in Accumulated Other Comprehensive Loss [Roll Forward]
Balance at beginning of period	(950)	$ (1,078)	(772)	$ (1,574)
Total other comprehensive (loss) income	(263)	190	(441)	686
Balance at end of period	(1,213)	(888)	(1,213)	(888)
Available-for-sale marketable securities
Increase (Decrease) in Accumulated Other Comprehensive Loss [Roll Forward]
Balance at beginning of period	1	7	4	6
Other comprehensive (loss) income	0	(2)	(3)	(1)
Balance at end of period	1	5	1	5
Total accumulated other comprehensive loss
Increase (Decrease) in Accumulated Other Comprehensive Loss [Roll Forward]
Balance at end of period	$ (1,212)	$ (883)	$ (1,212)	$ (883)