Fair Values Of Assets And Liabilities Fair Value of Assets and Liabilities (Narrative) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount Exluded From Money Market Funds	$ 2,642.4	$ 227.7