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Asset Retirement Obligation (Tables)
3 Months Ended
Mar. 31, 2012
Asset Retirement Obligation [Abstract]  
Asset Retirement Obligation
         
    (In millions)  

Asset retirement obligation at December 31, 2011

  $ 3,887  

Liabilities incurred

    109  

Liabilities settled

    (121

Accretion expense

    55  
   

 

 

 

Asset retirement obligation at March 31, 2012

    3,930  

Less current portion

    (448
   

 

 

 

Asset retirement obligation, long-term

  $ 3,482