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Asset Retirement Obligation (Tables)
 6 Months Ended
Jun. 30, 2011
Asset Retirement Obligation [Abstract]  
Asset Retirement Obligation
         
    (In millions)  
Asset retirement obligation at December 31, 2010
  $ 2,872  
Liabilities incurred
    186  
Liabilities settled
    (238 )
Accretion expense
    75  
 
   
Asset retirement obligation at June 30, 2011
    2,895  
 
       
Less current portion
    (360 )
 
   
 
       
Asset retirement obligation, long-term
  $ 2,535