Geographic Information and Major Customer and Product Data - Long-lived Assets by Geographic Region (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Long-lived assets	$ 12,593	$ 11,896
United States
Segment Reporting Information [Line Items]
Long-lived assets	7,163	7,072
Israel
Segment Reporting Information [Line Items]
Long-lived assets	3,514	2,944
France
Segment Reporting Information [Line Items]
Long-lived assets	1,306	1,426
Other
Segment Reporting Information [Line Items]
Long-lived assets	$ 610	$ 454