Employee Benefit Plans Change in Fair Value of Level 3 OPEB Assets (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Defined Benefit Plan Disclosure [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	$ 46.5	$ 35.7	$ 35.3
Fair Value Level 3 OPEB Assets Remaining Held at the Reporting Date	(0.5)	0.4
Defined Benefit Plan, Purchases, Sales, and Settlements	$ 11.3	$ 0