Debt and Interest (Details) (USD $) In Millions, unless otherwise specified								6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013 Commercial paper	Dec. 31, 2012 Commercial paper	Jun. 30, 2013 Notes payable	Dec. 31, 2012 Notes payable	Sep. 30, 2011 Multi-year credit facility	Jun. 30, 2013 New 364 day credit facility
Components of the company's debt obligations, along with applicable interest rate
Short-term debt			$ 642.8	$ 593.7	$ 61.7	$ 44.5
Long-term debt, current maturities	168.4	167.6
Short-term debt including current maturities of long-term debt	872.9	805.8
Maximum borrowing capacity, commercial paper before amendment							$ 1,500	$ 500
Term of credit facility								364 days