CONCENTRATION OF RISK - Revenues by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Concentration Risk [Line Items]
Revenues	$ 64,392	$ 58,092	$ 94,095	$ 89,315
South Korea [Member]
Concentration Risk [Line Items]
Revenues	61,196	53,822	87,142	76,033
China [Member]
Concentration Risk [Line Items]
Revenues	1,812	291	3,569	680
Japan [Member]
Concentration Risk [Line Items]
Revenues	800	2,886	2,104	10,656
Other [Member]
Concentration Risk [Line Items]
Revenues	405	576	1,018	1,204
Total Non-U.S. Locations [Member]
Concentration Risk [Line Items]
Revenues	64,213	57,575	93,833	88,573
UNITED STATES
Concentration Risk [Line Items]
Revenues	$ 179	$ 517	$ 262	$ 742