CONCENTRATION OF RISK - Revenues by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Concentration Risk [Line Items]
Revenues	$ 112,277	$ 87,765
South Korea [Member]
Concentration Risk [Line Items]
Revenues	69,425	61,499
China [Member]
Concentration Risk [Line Items]
Revenues	37,834	20,778
Japan [Member]
Concentration Risk [Line Items]
Revenues	1,787	1,846
Other Non-U.S. Locations [Member]
Concentration Risk [Line Items]
Revenues	497	583
Total Non-U.S. Locations [Member]
Concentration Risk [Line Items]
Revenues	109,543	84,706
United States [Member]
Concentration Risk [Line Items]
Revenues	$ 2,734	$ 3,059