Fair Value of Financial Instruments (Details 2) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Carrying amount, cost | 2011 term loan A
Debt
Debt	$ 656.6	$ 757.0
Carrying amount, cost | 2011 term loan B
Debt
Debt	978.2	1,128.0
Carrying amount, cost | 2020 Notes
Debt
Debt	496.6	496.5
Carrying amount, cost | Revolving Credit Facility
Debt
Debt	0	0
Carrying amount, cost | 2021 Notes
Debt
Debt	450.0
Fair value | 2011 term loan A
Debt
Debt	657.0
Fair value | 2011 term loan B
Debt
Debt	983.3
Fair value | 2020 Notes
Debt
Debt	543.1
Fair value | 2021 Notes
Debt
Debt	$ 461.2