Debt Debt (Short-Term Debt) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Short-term Debt [Line Items]
Short-term debt	$ 749.6	$ 0
Seven Hundred Fifty Million Fixed Rate Notes Due August Two Thousand Thirteen, Interest Equal To Five Point Four Zero Percent [Member]
Short-term Debt [Line Items]
Short-term debt	$ 749.6	$ 0