Fair Value Measurements (Details 3) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013 Fair Value, Measurements, Recurring [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member]	Mar. 31, 2012 Fair Value, Measurements, Recurring [Member]	Dec. 31, 2011 Fair Value, Measurements, Recurring [Member]
Business Acquisition, Contingent Consideration [Line Items]
Fair value, beginning of period			$ 293,700,000	$ 293,900,000	$ 269,900,000	$ 151,000,000
Additions	0	117,600,000
Fair Value Adjustment Of Contingent Consideration	2,277,000	1,258,000
Payments	(2,500,000)	0
Fair value, end of period			$ 293,700,000	$ 293,900,000	$ 269,900,000	$ 151,000,000