REVENUE (Contract Liabilities) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 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	21,013
Reclassification to revenues during the year	(17,014)
Balance, end of period	43,222
Less: long-term portion of deferred revenue	20,224	$ 18,665
Current portion, end of the period	22,998	$ 20,558
Revenue recognized	11,700
New deferred revenue during the year	5,300
Performance obligation	57,500
Assets related to costs related to obtain contracts	11,300
Amortization of capitalized contract costs	6,700
Unamortized balance of contract assets related to costs to obtain contracts	$ 4,600