|**Capitalized Exploratory Well Costs and Undeveloped Leasehold Costs (Tables)**                         | 6 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
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|**Extractive Industries [Abstract]**                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|Changes in Capitalized Exploratory Well Costs                                                           | Changes in capitalized exploratory well costs are as follows and exclude amounts that were capitalized and subsequently expensed in the same period:(millions)Six Months Ended June 30, 2017Capitalized Exploratory Well Costs, December 31, 2016$768Additions to Capitalized Exploratory Well Costs Pending Determination of Proved Reserves6Reclassified to Proved Oil and Gas Properties Based on Determination of Proved Reserves(1)(203)Capitalized Exploratory Well Costs, June 30, 2017$571(1)Amount relates to the approval and sanction of the first phase of development of the Leviathan field, offshore Israel. During second quarter 2017, we recorded Leviathan field proved undeveloped reserves of551MMBoe, net.
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|(millions)                                                                                              | Six Months Ended June 30, 2017                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Capitalized Exploratory Well Costs, December 31, 2016                                                   | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
|Additions to Capitalized Exploratory Well Costs Pending Determination of Proved Reserves                | 6                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
|Reclassified to Proved Oil and Gas Properties Based on Determination of Proved Reserves(1)              | (203                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
|Capitalized Exploratory Well Costs, June 30, 2017                                                       | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
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|(1)                                                                                                     | Amount relates to the approval and sanction of the first phase of development of the Leviathan field, offshore Israel. During second quarter 2017, we recorded Leviathan field proved undeveloped reserves of551MMBoe, net.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Aging of Capitalized Well Costs                                                                         | The following table provides an aging of capitalized exploratory well costs based on the date that drilling commenced:(millions)June 30, 2017December 31, 2016Exploratory Well Costs Capitalized for a Period of One Year or Less$19$69Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling(1)552699Balance at June 30, 2017$571$768(1)The decrease from December 31, 2016 is attributable to the reclassification of the Leviathan field to development work in process, partially offset by the capitalization of interest during the period on remaining exploratory wells.                                                                                                  
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|(millions)                                                                                              | June 30, 2017                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Exploratory Well Costs Capitalized for a Period of One Year or Less                                     | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
|Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling(1) | 552                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Balance at June 30, 2017                                                                                | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
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|(1)                                                                                                     | The decrease from December 31, 2016 is attributable to the reclassification of the Leviathan field to development work in process, partially offset by the capitalization of interest during the period on remaining exploratory wells.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         

X- DefinitionTabular disclosure of the change in capitalized exploratory costs during the period.
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