ACQUISITION (Details) (USD $)		0 Months Ended	12 Months Ended				12 Months Ended	0 Months Ended	12 Months Ended	0 Months Ended
	Apr. 26, 2012	May 03, 2012 LoopNet [Member]	Dec. 31, 2013 LoopNet [Member]	Dec. 31, 2012 LoopNet [Member]	Dec. 31, 2011 LoopNet [Member]	Apr. 30, 2012 LoopNet [Member] distinct_intangible_asset	Dec. 31, 2013 Acquired Customer Base [Member] distinct_intangible_asset	Apr. 30, 2012 Acquired Customer Base [Member] LoopNet [Member]	Dec. 31, 2013 Acquired Database Technology [Member]	Apr. 30, 2012 Acquired Database Technology [Member] LoopNet [Member]
Business Acquisition [Line Items]
Percentage of outstanding stock controlled by company						100.00%
Number of distinct intangible asset						1	1
Estimated useful life of acquired assets							10 years	10 years	5 years	5 years
Business combination, recognized goodwill acquired						$ 625,174,000
Goodwill tax deductible amount						0
Incurred acquisition-related costs			0	5,200,000	14,200,000
Term of consent order public comment period	30 days
Proceeds from sale of Xcelignet		4,200,000
Gain on sale of Xceligent		$ 0