Fair Value Measurements (Details 3) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014 Fair Value, Measurements, Recurring	Dec. 31, 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			$ 275,100,000	$ 280,900,000	$ 293,700,000	$ 293,900,000
Additions	0	0
Changes in fair value	(799,000)	2,277,000
Payments	(5,000,000)	(2,500,000)
Fair value, end of period			$ 275,100,000	$ 280,900,000	$ 293,700,000	$ 293,900,000