REVENUE (Contract Liabilities) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Change in Contract with Customer, Asset and Liability [Roll Forward]
Balance, beginning of the period	$ 39,223
New deferred revenue	32,551
Reclassification to revenues during the year	(26,192)
Balance, end of period	45,582
Less: long-term portion of deferred revenue	22,257	$ 18,665
Current portion, end of the period	23,325	$ 20,558
Revenue recognized	16,500
New deferred revenue during the year	9,700
Performance obligation	53,700
Assets related to costs related to obtain contracts	11,300
Amortization of capitalized contract costs	7,100
Unamortized balance of contract assets related to costs to obtain contracts	$ 4,200