REVENUES (Reconciliation of Deferred Revenue Balances) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
REVENUES [Abstract]
Balance at beginning of period	$ 189,052	$ 196,296	$ 192,783	$ 199,556
Revenue recognized from deferred revenue	(2,125)	(1,997)	(5,856)	(5,257)
Balance at end of period	$ 186,927	$ 194,299	$ 186,927	$ 194,299