CONCENTRATION OF RISK - Revenues by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Concentration Risk [Line Items]
Revenues	$ 134,000	$ 112,277
South Korea [Member]
Concentration Risk [Line Items]
Revenues	67,975	69,425
China [Member]
Concentration Risk [Line Items]
Revenues	60,504	37,834
Japan [Member]
Concentration Risk [Line Items]
Revenues	1,315	1,787
Other Non-U.S. Locations [Member]
Concentration Risk [Line Items]
Revenues	825	497
Total Non-U.S. Locations [Member]
Concentration Risk [Line Items]
Revenues	130,619	109,543
United States [Member]
Concentration Risk [Line Items]
Revenues	$ 3,381	$ 2,734