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Fair Value Disclosures (Carrying Amount and Estimated Fair Values of Financial Instruments) (Details) (USD $)
In Millions
Jun. 30, 2011
Dec. 31, 2010
Fair Value Disclosures    
Long-term investments, Carrying Amount $ 27.6 $ 26.7
Long-term investments, Estimated Fair Value 26.4 25.4
Long-term debt (including current portion), Carrying Amount 6,370.0 5,970.3
Long-term debt (including current portion), Estimated Fair Value $ 6,972.5 $ 6,482.4