OTHER NON-CURRENT ASSETS (Changes in Deferred Contract Costs) (Details) $ in Thousands	9 Months Ended
Sep. 30, 2018 USD ($)
Changes In Capitalized Contract Costs [Roll Forward]
Balance, beginning of period	$ 9,089
Add: costs deferred on new contracts	10,629
Less: amortization recorded in sales and marketing expenses	(8,351)
Balance, end of period	$ 11,367

Amount, after accumulated amortization and accumulated impairment loss, of asset recognized from cost incurred to obtain or fulfill contract with customer; classified as noncurrent.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 340
-SubTopic 40
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=68051541&loc=SL49131252-203054

Name:	us-gaap_CapitalizedContractCostNetNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant