INFORMATION ABOUT REVENUE AND GEOGRAPHIC AREAS (Long-Lived Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 103,651	$ 92,440	$ 84,168
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	100,990	89,362	78,675
All other countries
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 2,661	$ 3,078	$ 5,493