SEGMENT INFORMATION (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Segment information
Number of operating segments | segment									1
Disaggregation of revenue	$ 87,925	$ 96,633	$ 92,630	$ 93,896	$ 73,962	$ 80,092	$ 79,981	$ 76,576	$ 371,084	$ 310,611	$ 252,012
Identifiable assets	305,828				285,301				$ 305,828	$ 285,301
Total Revenue
Segment information
Percentage of concentration risk									16.00%	19.00%	18.00%
Trade receivables
Segment information
Percentage of concentration risk									17.00%	13.00%
Outside the United States
Segment information
Disaggregation of revenue									$ 159,365	$ 146,835	$ 119,212
Identifiable assets	$ 95,777				$ 88,400				95,777	88,400
Wholly owned foreign subsidiaries
Segment information
Disaggregation of revenue									$ 126,737	$ 126,104	$ 107,039