XML 35 R31.htm IDEA: XBRL DOCUMENT v3.3.0.814
Asset Retirement Obligations (Tables)
 9 Months Ended
Sep. 30, 2015
Asset Retirement Obligation Disclosure [Abstract]  
Changes in Asset Retirement Obligations
Changes in ARO are as follows:
 
Nine Months Ended
September 30,
(millions)
2015
 
2014
Asset Retirement Obligations, Beginning Balance
$
751

 
$
586

Liabilities Incurred
54

 
38

Liabilities Settled
(29
)
 
(77
)
Revision of Estimate
79

 
123

Accretion Expense (1)
32

 
28

Asset Retirement Obligations, Ending Balance
$
887

 
$
698

(1) Accretion expense is included in DD&A expense in the consolidated statements of operations.