GOODWILL AND INTANGIBLE ASSETS (Schedule of Intangible Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 25,647	$ 50,045
Accumulated Amortization	(8,754)	(17,434)
Total amortization	16,893	32,611
Business relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	9,918	17,400
Accumulated Amortization	(896)	(2,741)
Total amortization	$ 9,022	$ 14,659
Weighted Average Remaining Life (in years)	10 years 3 months 1 day	10 years 1 month 1 day
Developed technology
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 7,832	$ 9,280
Accumulated Amortization	(2,071)	(4,122)
Total amortization	$ 5,761	$ 5,158
Weighted Average Remaining Life (in years)	4 years 1 month 6 days	3 years 1 month 6 days
Content
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 4,005	$ 3,674
Accumulated Amortization	(3,610)	(2,581)
Total amortization	$ 395	$ 1,093
Weighted Average Remaining Life (in years)	1 year 10 months 6 days	2 years
Domain and data licenses
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 2,869	$ 2,804
Accumulated Amortization	(1,847)	(1,340)
Total amortization	$ 1,022	$ 1,464
Weighted Average Remaining Life (in years)	2 years 2 months 6 days	3 years
Trademarks
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 877	$ 3,338
Accumulated Amortization	(287)	(1,861)
Total amortization	$ 590	$ 1,477
Weighted Average Remaining Life (in years)	2 years 2 months 6 days	2 years 1 month 6 days
User relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 146	$ 12,000
Accumulated Amortization	(43)	(3,240)
Total amortization	$ 103	$ 8,760
Weighted Average Remaining Life (in years)	2 years 2 months 6 days	5 years 1 month 6 days
Advertiser relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount		$ 1,549
Accumulated Amortization		(1,549)
Total amortization		$ 0
Weighted Average Remaining Life (in years)		0 years