ORGANIZATION	12 Months Ended
Dec. 31, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]
ORGANIZATION	ORGANIZATION CoStar Group, Inc. (the “Company” or “CoStar”) provides information, analytics and marketing services to the commercial real estate and related business community through its comprehensive, proprietary database of commercial real estate information covering the United States (“U.S.”) and parts of the United Kingdom ("U.K.") and France, as well as its complementary online marketplace of commercial real estate listings. The Company operates within two operating segments, U.S. and International, and its services are typically distributed to its clients under subscription-based license agreements that renew automatically, a majority of which have a term of one year.

ORGANIZATION

12 Months Ended

Dec. 31, 2013

Organization, Consolidation and Presentation of Financial Statements [Abstract]

CoStar Group, Inc. (the “Company” or “CoStar”) provides information, analytics and marketing services to the commercial real estate and related business community through its comprehensive, proprietary database of commercial real estate information covering the United States (“U.S.”) and parts of the United Kingdom ("U.K.") and France, as well as its complementary online marketplace of commercial real estate listings. The Company operates within two operating segments, U.S. and International, and its services are typically distributed to its clients under subscription-based license agreements that renew automatically, a majority of which have a term of one year.