Derivative Instruments and Hedging Activities Asset and Liability Derivative Instruments Designated as Hedges in the Balance Sheets (Details) (Fair Value Hedging [Member], Interest Rate Derivative Instruments [Member], Level 2 [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Derivatives, Fair Value [Line Items]
Consolidated total, derivative assets	$ 8.9	$ 0
Prepaid Expenses and Other [Member]
Derivatives, Fair Value [Line Items]
Interest rate derivative instrument, Current	1.1	0
Other Noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Interest rate derivative instrument, Noncurrent	$ 7.8	$ 0