XML 71 R54.htm IDEA: XBRL DOCUMENT v3.8.0.1
Asset Retirement Obligations (Details) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Dec. 31, 2017
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]      
Beginning asset retirement obligations $ 271 $ 297  
New wells placed on production 1 1  
Changes in estimates 2 0  
Obligations reclassified to liabilities held for sale (6) 0  
Liabilities settled (9) (6)  
Accretion of discount 4 5  
Ending asset retirement obligations 263 $ 297  
Asset retirement obligations, current portions $ 40   $ 41