ACQUISITION (Details) (USD $)
0 Months Ended 3 Months Ended
Apr. 03, 2014
Mar. 31, 2015
Mar. 31, 2014
Dec. 31, 2014
Dec. 31, 2013
Apr. 01, 2014
Business Acquisition [Line Items]            
Payments to acquire businesses $ 587,104,000          
Closing purchase price adjustments 2,104,000          
Post closing purchase price adjustments 2,886,000          
Goodwill   1,137,707,000   1,138,805,000 718,587,000  
Apartments.com [Member]            
Business Acquisition [Line Items]            
Goodwill           421,724,000
Goodwill tax deductible amount           421,724,000
Business combination, acquisition related costs   $ 0 $ 1,100,000      
Customer Contracts [Member]            
Business Acquisition [Line Items]            
Estimated useful life of acquired assets   10 years        
Customer Contracts [Member] | Apartments.com [Member]            
Business Acquisition [Line Items]            
Number of distinct intangible assets           1
Estimated useful life of acquired assets 10 years          
Developed Technology Rights [Member]            
Business Acquisition [Line Items]            
Estimated useful life of acquired assets   5 years        
Developed Technology Rights [Member] | Apartments.com [Member]            
Business Acquisition [Line Items]            
Estimated useful life of acquired assets 1 year          
Trade Names and Other Intangible Assets [Member]            
Business Acquisition [Line Items]            
Estimated useful life of acquired assets   13 years        
Trade Names and Other Intangible Assets [Member] | Apartments.com [Member]            
Business Acquisition [Line Items]            
Estimated useful life of acquired assets 13 years          
Building Photography [Member]            
Business Acquisition [Line Items]            
Estimated useful life of acquired assets   5 years        
Building Photography [Member] | Apartments.com [Member]            
Business Acquisition [Line Items]            
Estimated useful life of acquired assets 3 years