REVENUES (Reconciliation of Deferred Revenue Balances) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
REVENUES [Abstract]
Balance at beginning of period	$ 176,293	$ 183,997	$ 177,962	$ 185,339
Revenue recognized from deferred revenue	(2,217)	(2,034)	(3,886)	(3,376)
Balance at end of period	$ 174,076	$ 181,963	$ 174,076	$ 181,963