CONCENTRATION OF RISK - Revenues by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Concentration Risk [Line Items]
Revenues	$ 143,618	$ 117,079	$ 407,278	$ 287,324
South Korea [Member]
Concentration Risk [Line Items]
Revenues	95,741	66,667	250,040	167,154
China [Member]
Concentration Risk [Line Items]
Revenues	41,323	43,569	138,135	101,911
Japan [Member]
Concentration Risk [Line Items]
Revenues	1,911	2,279	5,227	6,263
Other Non-U.S. Locations [Member]
Concentration Risk [Line Items]
Revenues	537	663	2,257	1,475
Total Non-U.S. Locations [Member]
Concentration Risk [Line Items]
Revenues	139,512	113,178	395,659	276,803
United States [Member]
Concentration Risk [Line Items]
Revenues	$ 4,106	$ 3,901	$ 11,619	$ 10,521