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Receivables (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Allowance for bad debts [Roll forward]      
Balance at Beginning of Period $ 91 $ 90 $ 60
Charged to Costs and Expenses 53 5 37
Write-Offs (7) (4) (7)
Balance at End of Period $ 137 $ 91 $ 90
Geographic Concentration Risk [Member] | United States [Member] | Gross Trade Receivables [Member]
     
Concentration Risk [Line Items]      
Concentration risk, percentage (in hundredths) 45.00% 36.00%  
Geographic Concentration Risk [Member] | Other Countries [Member] | Gross Trade Receivables [Member]
     
Concentration Risk [Line Items]      
Maximum percentage of gross trade receivables from one geographic segment (in hundredths) 10.00% 10.00%  
Customer Concentration Risk [Member] | Gross Trade Receivables [Member]
     
Concentration Risk [Line Items]      
Maximum percentage of gross trade receivables from one customer (in hundredths) 10.00% 10.00%