Fair Value Measurements (Details 3) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 Fair Value, Measurements, Recurring	Mar. 31, 2014 Fair Value, Measurements, Recurring	Dec. 31, 2013 Fair Value, Measurements, Recurring	Jun. 30, 2013 Fair Value, Measurements, Recurring	Mar. 31, 2013 Fair Value, Measurements, Recurring	Dec. 31, 2012 Fair Value, Measurements, Recurring
Business Acquisition, Contingent Consideration [Line Items]
Fair value, beginning of period					$ 279,100,000	$ 275,100,000	$ 280,900,000	$ 281,000,000	$ 293,700,000	$ 293,900,000
Additions	0	0	0	0
Changes in fair value	4,019,000	(5,163,000)	3,220,000	(2,886,000)
Payments	0	(7,500,000)	(5,000,000)	(10,000,000)
Fair value, end of period					$ 279,100,000	$ 275,100,000	$ 280,900,000	$ 281,000,000	$ 293,700,000	$ 293,900,000