REVENUES (Reconciliation of Deferred Revenue Balances) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
REVENUES [Abstract]
Balance at beginning of period	$ 183,997	$ 191,131	$ 185,339	$ 192,783
Revenue recognized from deferred revenue	(2,034)	(2,079)	(3,376)	(3,731)
Balance at end of period	$ 181,963	$ 189,052	$ 181,963	$ 189,052