UNEARNED REVENUE (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Change in Contract with Customer, Liability [Roll Forward]
Balance, beginning of period	$ 117,614	$ 106,323
Deferral of unearned revenue	166,053	151,139
Recognition of unearned revenue	(156,592)	(139,848)
Balance, end of period	127,075	117,614
Long-term unearned revenue	$ 11,100	$ 8,600
Long-term unearned revenue, recognition period (or less)	5 years