Fair Value Measurements (Details 3) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Fair Value, Measurements, Recurring [Member]	Mar. 31, 2013 Fair Value, Measurements, Recurring [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member]	Jun. 30, 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					$ 281,000,000	$ 293,700,000	$ 293,900,000	$ 280,900,000	$ 269,900,000	$ 151,000,000
Additions	0	4,600,000	0	122,200,000
(Gain) loss on fair value remeasurement of contingent consideration	(5,163,000)	12,858,000	(2,886,000)	14,117,000
Payments	(7,500,000)	(6,500,000)	(10,000,000)	(6,500,000)
Fair value, end of period					$ 281,000,000	$ 293,700,000	$ 293,900,000	$ 280,900,000	$ 269,900,000	$ 151,000,000