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Asset Retirement Obligations Asset Retirement Obligations (Tables)
 9 Months Ended
Sep. 30, 2013
Asset Retirement Obligation Disclosure [Abstract]  
Schedule of Change in Asset Retirement Obligation [Table Text Block]
The following summarizes the changes in asset retirement obligations during the first nine months of 2013:
(In millions)
 
Beginning balance(a)
$
1,783

Incurred, including acquisitions
10

Settled, including dispositions
(41
)
Accretion expense (included in depreciation, depletion and amortization)
103

Revisions to previous estimates
306

Held for sale
(41
)
Ending balance(a)
$
2,120


(a) Beginning and ending balances include asset retirement obligations of $34 million and $93 million classified as short-term at December 31, 2012 and September 30, 2013.