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Asset Retirement Obligations (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2014
Mar. 31, 2013
Dec. 31, 2013
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]      
Beginning asset retirement obligations $ 194 $ 198  
Asset Retirement Obligation, Liabilities Incurred 1 3  
Changes in estimates 1 (6)  
Disposition of wells (1) (4)  
Liabilities settled (4) (3)  
Accretion of discount from continuing operations 3 3  
Ending asset retirement obligations 194 191  
Asset retirement obligations, current portions $ 19   $ 19