Debt (Schedule Of Long-Term Debt) (Details) (USD $) In Millions, unless otherwise specified					6 Months Ended
	Jun. 30, 2012		Dec. 31, 2011		Jun. 30, 2012 Revolving Credit Facility Maturing In December 2012 [Member]	Jun. 30, 2012 Commercial Paper [Member]
Debt Instrument [Line Items]
Revolving credit facilities	$ 375.0		$ 100.0
Commercial paper	732.3	[1]	480.1	[1]
Term loan	26.7		29.2
Property financing	7.3		7.3
Total long-term debt	1,141.3		616.6
Less: current portion	(27.2)		(580.6)
Long-term debt, less current portion	1,114.1		36.0
Maximum capacity for letters of credit under credit facility					$ 600.0
Maturity date					Dec. 01, 2012
Long-term Debt, Weighted Average Interest Rate						0.40%

[1] At December 31, 2011, debt outstanding from our $600.0 million five-year revolving credit facility and outstanding commercial paper were classified as short-term due to the credit facility’s maturity in December 2012. At June 30, 2012, committed credit available under our new credit agreement provided the ability to refinance our commercial paper obligations on a long-term basis. As we have both the ability and intent to refinance these obligations on a long-term basis, our commercial paper borrowings were classified as long-term in the condensed consolidated balance sheet at June 30, 2012. Our commercial paper borrowings as of June 30, 2012, had a weighted average interest rate of 0.40%.