Property, Plant and Equipment (Tables)
 3 Months Ended
Mar. 31, 2015
Oil and Gas Exploration and Production Industries Disclosures [Abstract]  
Schedule of changes in net asset retirement liability
The net asset retirement liability as of March 31, 2015 on our consolidated balance sheet in other current and non-current liabilities and the changes in the net liability from January 1 through March 31, 2015 were as follows:
 
2015
 
(in millions)
Net asset retirement liability at January 1
$
42

Liabilities incurred
1

Liabilities settled
(1
)
Accretion expense
1

Net asset retirement liability at March 31
$
43