XML 67 R33.htm IDEA: XBRL DOCUMENT v3.8.0.1
Asset Retirement Obligations (Tables)
 12 Months Ended
Dec. 31, 2017
Asset Retirement Obligation Disclosure [Abstract]  
Schedule of Change in Asset Retirement Obligation
Changes in AROs were as follows:
 
Year Ended December 31,
(millions)
2017
 
2016
Asset Retirement Obligations, Beginning Balance
$
935

 
$
989

Liabilities Incurred
94

 
21

Liabilities Settled
(82
)
 
(120
)
Revision of Estimate
(65
)
 
(3
)
Reclassification to Liabilities Associated with Assets Held for Sale
(54
)
 
—

Accretion Expense
47

 
48

Asset Retirement Obligations, Ending Balance
$
875

 
$
935