Investments in Affiliates Investment Interest Joint Venture (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2011 years payment	Jun. 30, 2011	Mar. 31, 2011	May 30, 2011 RP Data [Member]
Business Acquisition, Percentage of Voting Interests Acquired			50.10%
Business Acquisition, Cost of Acquired Entity, Purchase Price		$ 35.0
Payments to Acquire Interest in Joint Venture		20.0
Joint Venture Deferred Purchase Price		15.0
Number Of Joint Venture Interest Acquisition Deferred Installment Payment	3
Joint Venture Deferred Payment Installment Amount		5.0
Joint Venture Deferred Payment Discounted Amount		12.7
Business Acquisition, Preexisting Relationship, Gain (Loss) Recognized				$ 58.9