SEGMENT AND GEOGRAPHICAL INFORMATION (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) segment	Jun. 30, 2017 USD ($)
Segment and geographical information
Number of segments | segment			1
Revenues	$ 71,026	$ 68,038	$ 139,903	$ 134,593
Americas
Segment and geographical information
Revenues	40,831	39,952	82,507	81,057
Europe
Segment and geographical information
Revenues	24,047	21,504	45,801	41,711
Asia Pacific
Segment and geographical information
Revenues	$ 6,148	$ 6,582	$ 11,595	$ 11,825