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Receivables (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Concentration Risk [Line Items]      
Maximum Percentage Gross Trade Receivables From One Geographic Segment 10.00% 10.00%  
Maximum Percentage Gross Trade Receivables From One Customer 10.00% 10.00%  
Allowance for Doubtful Accounts Receivable [Roll Forward]      
Balance at Beginning of Period $ 137 $ 91 $ 90
Charged to Costs and Expenses (40) 53 5
Write-Offs (5) (7) (4)
Balance at End of Period $ 92 $ 137 $ 91
Geographic Concentration Risk | United States | Accounts Receivable
     
Concentration Risk [Line Items]      
Concentration Risk, Percentage (in hundredths) 36.00% 45.00%