|**Divestitures**                                         | 3 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
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|**Divestitures [Abstract]**                              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Divestitures                                             | DivestituresOnshore US PropertiesDuring the firstthreemonths of 2015, we sold certain onshore US crude oil and natural gas leases. Properties sold generated net proceeds of$119 million, which were applied to the DJ Basin depletable field, with no recognition of gain or loss.Information regarding assets sold during the first three months of 2014 is as follows:Three Months Ended March 31,(millions)2014Sales Proceeds$92LessNet Book Value of Assets Sold(106)Goodwill Allocated to Assets Sold(6)Asset Retirement Obligations Associated with Assets Sold20Other Closing Adjustments(1)Gain on Divestitures$(1)
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|                                                         | Three Months Ended March 31,                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                
|(millions)                                               | 2014                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Sales Proceeds                                           | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Less                                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Net Book Value of Assets Sold                            | (106                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Goodwill Allocated to Assets Sold                        | (6                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Asset Retirement Obligations Associated with Assets Sold | 20                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Other Closing Adjustments                                | (1                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Gain on Divestitures                                     | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           

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                    duration X- DefinitionTabular disclosure of all information related to any significant acquisition and disposal. Disclosure may include methodology and assumptions, type of asset, asset classification, useful life, useful purpose, acquisition cost, method of acquisition or disposal, depreciation method, gain (loss) on disposal pretax and net of tax, date of acquisition or disposal and restrictions on amount of proceeds from donated assets.+ ReferencesReference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6360339&loc=d3e1361-107760+ Details**Name:**
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