Derivative Instruments and Hedging Activities (Details 1) (Interest rate swaps [Member], Derivatives in Cash Flow Hedging Relationships [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Interest rate swaps [Member] | Derivatives in Cash Flow Hedging Relationships [Member]
Summary of Cash Flow Hedges
Amount of Gains or (Loss) Recognized is OCI on Derivatives, net of tax (Effective Portion)	$ 0.2	$ 0.5