REVENUES (Reconciliation of Deferred Revenue Balances) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
REVENUES [Abstract]
Balance at beginning of period	$ 192,783	$ 199,556	$ 206,468
Revenue recognized from deferred revenue	(7,444)	(6,773)	(6,912)
Balance at end of period	$ 185,339	$ 192,783	$ 199,556