|**Income Taxes**                     | 6 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
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|**Income Tax Disclosure [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|Income Taxes                         | 10. Income TaxesThe income tax provision (benefit) consists of the following:Three Months Ended June 30,Six Months Ended June 30,(millions)2017201620172016Current(1)$37$45$49$65Deferred(873)(228)(873)(414)Total Income Tax Benefit$(836)$(183)$(824)$(349)Effective Tax Rate35.8%36.7%36.2%36.7%(1)Current income taxes are attributable to our operations in Israel and Equatorial Guinea.Effective Tax Rate (ETR)At the end of each interim period, we apply a forecasted annualized effective tax rate (ETR) to current year earnings or loss before tax, which can result in significant interim ETR fluctuations. Our ETR for thethree and sixmonths endedJune 30, 2017varied as compared with thethree and sixmonths endedJune 30, 2016primarily due to a larger discrete tax benefit in the prior year driven by a tax rate change in a foreign jurisdiction. In addition, the significant increase in the deferred tax benefit for the three and six months ended June 30, 2017 is primarily due to the loss recorded for the Marcellus Shale upstream divestiture.In our major tax jurisdictions, the earliest years remaining open to examination are as follows: US –2013, Israel –2015andEquatorial Guinea –2011.
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|                                     | Three Months Ended June 30,                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|(millions)                           | 2017                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
|Current(1)                           | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
|Deferred                             | (873                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
|Total Income Tax Benefit             | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
|Effective Tax Rate                   | 35.8                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            

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