Fair Value Measurements (Details 2) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Summary of fair and carrying value of debt instruments
Credit facility, amount outstanding	$ 200.0	$ 0
Notes payable, Carrying Value	802.3	1,054.3
Notes payable, Fair Value	889.4	1,155.3
Notes Payable to Fumedica [Member]
Summary of fair and carrying value of debt instruments
Notes payable, Fair Value	19.3	20.0
Notes payable, Carrying Value	17.5	17.9
6.0% Senior Notes due 2013 [Member]
Summary of fair and carrying value of debt instruments
Notes payable, Fair Value	0	453.7
Notes payable, Carrying Value	0	450.0
6.875% Senior Notes due 2018 [Member]
Summary of fair and carrying value of debt instruments
Notes payable, Fair Value	670.1	681.6
Notes payable, Carrying Value	$ 584.8	$ 586.4