GEOGRAPHIC INFORMATION AND REVENUES BY PRODUCT GROUP - Revenue by geographic region (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) segment	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Segment Reporting [Abstract]
Number of reportable segments | segment	1
Revenues by geographic region
Total revenue	$ 863,893	$ 857,498	$ 658,140
United States
Revenues by geographic region
Total revenue	327,528	386,360	300,674
China
Revenues by geographic region
Total revenue	172,405	192,581	152,739
Europe
Revenues by geographic region
Total revenue	176,937	149,855	93,666
Other Americas
Revenues by geographic region
Total revenue	92,449	52,447	24,692
Other Asia
Revenues by geographic region
Total revenue	$ 94,574	$ 76,255	$ 86,369