REVENUES (Reconciliation of Deferred Revenue Balances) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
REVENUES [Abstract]
Balance at beginning of period	$ 174,076	$ 181,963	$ 177,962	$ 185,339
Revenue recognized from deferred revenue	(2,022)	(2,046)	(5,908)	(5,422)
Balance at end of period	$ 172,054	$ 179,917	$ 172,054	$ 179,917