Derivative Instruments and Hedging Activities (Details) (Other long-term liabilities [Member], Derivatives designated as hedging instruments [Member], Interest rate swaps [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Other long-term liabilities [Member] | Derivatives designated as hedging instruments [Member] | Interest rate swaps [Member]
Liability Derivatives
Fair value of Derivative liability	$ (8.7)	$ (9.0)