Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Increase (Decrease) in Accumulated Other Comprehensive Loss [Roll Forward]
Balance at beginning of period			$ 34,341
Balance at end of period	$ 32,421		32,421
Foreign currency translation
Increase (Decrease) in Accumulated Other Comprehensive Loss [Roll Forward]
Balance at beginning of period	(356)	$ (1,458)	(772)	$ (1,574)
Total other comprehensive (loss) income	(594)	380	(178)	496
Balance at end of period	(950)	(1,078)	(950)	(1,078)
Available-for-sale marketable securities
Increase (Decrease) in Accumulated Other Comprehensive Loss [Roll Forward]
Balance at beginning of period	3	7	4	6
Other comprehensive (loss) income	(2)	0	(3)	1
Balance at end of period	1	7	1	7
Total accumulated other comprehensive loss
Increase (Decrease) in Accumulated Other Comprehensive Loss [Roll Forward]
Balance at end of period	$ (949)	$ (1,071)	$ (949)	$ (1,071)