DESCRIPTION OF BUSINESS AND BASIS FOR PRESENTATION (Narrative) (Details)	3 Months Ended
	Mar. 31, 2018
Capitalized Contract Cost [Line Items]
Contracts invoiced in arrears, duration	1 month
Capitalized contract cost, amortization period threshold for practical expedient	12 months
Maximum
Capitalized Contract Cost [Line Items]
Capitalized contract cost, amortization period	41 months
Advertising services
Capitalized Contract Cost [Line Items]
Contracts invoiced in arrears, duration	1 month
Payment collection after billing period, duration	30 days
Transaction services
Capitalized Contract Cost [Line Items]
Payment collection after billing period, duration	30 days
Subscription services
Capitalized Contract Cost [Line Items]
Contracts invoiced in advance, duration	1 month