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Asset Retirement Obligations (Notes)
 12 Months Ended
Dec. 31, 2013
Asset Retirement Obligation Disclosure [Abstract]  
Asset Retirement Obligations
Asset Retirement Obligations
The following summarizes the changes in asset retirement obligations:
(In millions)
2013
 
2012
Beginning balance
$
1,783

 
$
1,510

Incurred, including acquisitions
84

 
150

Settled, including dispositions
(78
)
 
(35
)
Accretion expense (included in depreciation, depletion and amortization)
106

 
91

Revisions to previous estimates
244

 
150

Held for sale
(43
)
 
(83
)
Ending balance(a)
$
2,096

 
$
1,783

(a) 
Includes asset retirement obligations of $87 million and $34 million classified as short-term at December 31, 2013 and 2012.