Capitalized Data and Database Development Costs, Net (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Research And Development [Line Items]
Capitalized data and database costs gross	$ 444,516,000	$ 332,897,000
Capitalized data and database costs accumulated amortization	(140,510,000)	(121,566,000)
Capitalized data and database costs, net	304,006,000	211,331,000
Amortization	23,200,000	17,700,000	16,100,000
Capitalized Data [Member]
Research And Development [Line Items]
Capitalized data and database costs gross	373,333,000	261,074,000
Capitalized Data From Acquisitions [Member]
Research And Development [Line Items]
Capitalized data and database costs gross	91,400,000
Geospatial Data [Member]
Research And Development [Line Items]
Capitalized data and database costs gross	52,916,000	52,916,000
Eviction Data [Member]
Research And Development [Line Items]
Capitalized data and database costs gross	$ 18,267,000	$ 18,907,000