LONG-TERM DEBT (Details) (USD $)	0 Months Ended	12 Months Ended			27 Months Ended	12 Months Ended				0 Months Ended		0 Months Ended					0 Months Ended
	Feb. 16, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013	Dec. 31, 2013 New Term Loan [Member]	Dec. 31, 2012 New Term Loan [Member]	Dec. 31, 2011 New Term Loan [Member]	Feb. 16, 2012 CoStar Group [Member] LoopNet [Member] Committed Term Loan [Member]	Feb. 16, 2012 CoStar Group [Member] LoopNet [Member] New Term Loan [Member]	Apr. 30, 2012 CoStar Group [Member] LoopNet [Member] New Term Loan [Member]	Feb. 16, 2012 CoStar Group [Member] LoopNet [Member] New Revolving Credit Facility [Member]	Feb. 16, 2012 Minimum [Member]	Feb. 16, 2012 Maximum [Member]	Feb. 16, 2012 Maximum [Member] CoStar Group [Member] Swingline Loan [Member]	Feb. 16, 2012 Maximum [Member] CoStar Group [Member] Letter of Credit [Member]	Feb. 16, 2012 Federal Funds Rate [Member]	Feb. 16, 2012 LIBOR [Member]
Business Acquisition [Line Items]
Debt instrument borrowing capacity										$ 175,000,000		$ 50,000,000
Term of loan (in years)										5 years		5 years
Line of credit facility, amount outstanding		0	0		0						175,000,000
Revolving credit sub-facility for swing-line loans															5,000,000	10,000,000
Annual amortization, first year after closing (in percent)									5.00%
Annual amortization, second year after closing (in percent)									10.00%
Annual amortization, third year after closing (in percent)									15.00%
Annual amortization, fourth year after closing (in percent)									20.00%
Annual amortization, fifth year after closing (in percent)									50.00%
Basis spread on federal funds rate (in percent)																	0.50%	2.00%
LIBOR period (in months)	1 month
Basis spread on variable rate, one month interest period (in percent)																		1.00%
Basis spread on variable rate, per annum (in percent)																		1.00%
Default interest rate per annum on overdue amounts (in percent)	2.00%
Maximum debt service coverage ratio (in percent)	150.00%
Maximum total leverage ratio for fifth through eighth quarters after closing date (in percent)	275.00%
Maximum total leverage ratio after eight fiscal quarters (in percent)	250.00%
Excess cash flow payment maturity period within issuance of financial statements	10 days
First excess cash flow repayment percentage	50.00%
First excess cash flow repayment requirement (in percent)													300.00%
Second excess cash flow repayment requirement (in percent)													250.00%	300.00%
Second excess cash flow repayment percentage	25.00%
Third excess cash flow repayment requirement (in percent)														250.00%
Third excess cash flow repayment percentage	0.00%
Unamortized debt issuance expense		11,500,000			11,500,000
Debt issuance underwriting fees					9,200,000
Legal fees associated with the debt issuance					2,300,000
Debt interest expense						6,943,000	4,832,000	0
Amortization of debt issuance costs		3,014,000	1,989,000	0
Interest paid		$ 4,291,000	$ 2,480,000	$ 0