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Investments (Narrative) (Details) (USD $)
In Millions, unless otherwise specified
Sep. 30, 2012
Dec. 31, 2011
Categories of Investments, Marketable Securities, Trading Securities
   
Investments held in our rabbi trusts $ 90 $ 90
Categories of Investments, Cost-method Investments
   
Investments held in our rabbi trusts $ 15 $ 17