Acquisitions (Details)	6 Months Ended				1 Months Ended		3 Months Ended	1 Months Ended			3 Months Ended		3 Months Ended
	Jun. 30, 2011 USD ($)	Jun. 30, 2011 RP Data [Member] Data and Analytics [Member] USD ($)	Mar. 31, 2011 Dorado Network Systems [Member] USD ($)	Dec. 31, 2010 Dorado Network Systems [Member] USD ($)	Jan. 31, 2011 Dorado Network Systems [Member] Customer Lists [Member] years	Mar. 31, 2011 Dorado Network Systems [Member] Customer Lists [Member] USD ($)	Mar. 31, 2011 Dorado Network Systems [Member] Trade Names [Member] USD ($) years	Jan. 31, 2011 RP Data [Member] USD ($)	May 30, 2011 RP Data [Member] USD ($)	May 30, 2011 RP Data [Member] AUD	Jun. 30, 2011 RP Data [Member] Customer Lists [Member] years	May 30, 2011 RP Data [Member] Customer Lists [Member] USD ($)	Jun. 30, 2011 RP Data [Member] Trade Names [Member] years	May 30, 2011 RP Data [Member] Trade Names [Member] USD ($)
Business Acquisition [Line Items]
Business Acquisition, Cost of Acquired Entity, Cash Paid			$ 31,600,000
Business Acquisition, Percentage of Voting Interests Acquired				39.00%					40.20%	40.20%
Business Acquisition, Preexisting Relationship, Gain (Loss) Recognized				14,500,000					58,900,000
Business Acquisition, Purchase Price Allocation, Goodwill Amount			18,900,000
Business Acquisition Purchase Price Allocation Developed Software						20,400,000	3,200,000					46,700,000		11,700,000
Acquired Finite-lived Intangible Asset, Weighted Average Useful Life					12		5				8		10
Business Acquisition, Contingent Consideration, Potential Cash Payment									157,200,000	147,200,000
Goodwill, Acquired During Period	181,780,000	162,882,000
Notional Amount of Foreign Currency Derivatives										180,300,000
Business Acquisition Recognized Marked To Market Gain								$ 1,800,000