|**Asset Impairments (Notes)**         | 3 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
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|**Asset Impairments [Abstract]**      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Asset Impairment Charges [Text Block] | 4. Asset ImpairmentsPre-tax (non-cash) asset impairment charges were as follows:Three Months Ended March 31,(millions)20142013North Sea Property$92$—Non-Core US Property5—Total$97$—During first quarter 2014, we recorded pre-tax asset impairment expense of$97 million. Approximately$92 millionwas related to the North Sea. In March 2014, the operator of one of the remaining fields notified the working interest owners that expected field abandonment costs would be higher than originally projected. The operator also notified the working interest owners that it would begin working with the appropriate regulatory agency for approval of cessation of production and subsequent field abandonment sooner than anticipated.As a result of this new information, we adjusted the asset retirement obligation to reflect the updated estimate of abandonment  costs and timing. We assessed the asset for impairment and determined that it was impaired. The impairment charge was included in consolidated income from continuing operations.See Note2. Basis of PresentationandNote7. Fair Value Measurements and Disclosures.
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|                                      | Three Months Ended March 31,                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|(millions)                            | 2014                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|North Sea Property                    | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|Non-Core US Property                  | 5                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|Total                                 | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 

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