Goodwill Additional Data (Details) (USD $)	12 Months Ended						1 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 Data and Analytics [Member]	Dec. 31, 2010 Data and Analytics [Member]	Dec. 31, 2009 Data and Analytics [Member]	Dec. 31, 2011 Dorado Network Systems [Member]	May 31, 2011 RP Data [Member] Data and Analytics [Member]	Sep. 30, 2011 Tarasoft [Member]	Nov. 30, 2010 RealtyBid [Member]
Goodwill and Intangible Assets Disclosure [Abstract]
Business Acquisition, Purchase Price Allocation, Goodwill Amount					$ 2,300,000	$ 19,700,000
Statement [Line Items]
Goodwill, Acquired During Period	192,083,000	13,622,000	172,419,000	0			154,500,000	17,900,000	12,100,000
Goodwill reclassified to assets of discontinued operations	17,300,000	155,100,000
Discount rate used in weighted average cost of capital calculation	12.00%
Control premium	20.00%
Business Acquisition, Purchase Price Allocation, Goodwill Amount					$ 2,300,000	$ 19,700,000