| **Capitalized Exploratory Well Costs (Details) (USD $)In Millions, unless otherwise specified**                                                                                                                                                                                                                                                                                                                                  | 12 Months Ended |
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| **Capitalized Exploratory Well Costs [Abstract]**                                                                                                                                                                                                                                                                                                                                                                                |            |  |   |  |   |  |
| Capitalized Exploratory Well Costs, Beginning of Period                                                                                                                                                                                                                                                                                                                                                                          | $ 900           |  | $ 696 |  | $ 466 |  |
| Additions to Capitalized Exploratory Well Costs Pending Determination of Proved Reserves                                                                                                                                                                                                                                                                                                                                         | 581             |  | 360 |  | 322 |  |
| Reclassified to Proved Oil and Gas Properties Based on Determination of Proved Reserves (1)                                                                                                                                                                                                                                                                                                                                      | (177)           | [1] | (18) |  | (55) |  |
| Capitalized Exploratory Well Costs Charged to Expense                                                                                                                                                                                                                                                                                                                                                                            | (3)             | [2] | (114) | [2] | (37) | [2] |
| Other                                                                                                                                                                                                                                                                                                                                                                                                                            | 0               | [3] | (24) | [3] | 0 | [3] |
| Capitalized Exploratory Well Costs, End of Period                                                                                                                                                                                                                                                                                                                                                                                | 1,301           |  | 900 |  | 696 |  |
| **Capitalized Exploratory Well Costs Aging [Abstract]**                                                                                                                                                                                                                                                                                                                                                                          |            |  |   |  |   |  |
| Exploratory Well Costs Capitalized for a Period of One Year or Less                                                                                                                                                                                                                                                                                                                                                              | 568             |  | 355 |  | 318 |  |
| Capitalized Exploratory Well Costs that Have Been Capitalized for Period Greater than One Year                                                                                                                                                                                                                                                                                                                                   | 733             |  | 545 |  | 378 |  |
| Capitalized Exploratory Well Costs,                                                                                                                                                                                                                                                                                                                                                                                              | $ 1,301         |  | $ 900 |  | $ 696 |  |
| Number of Projects with Exploratory Well Costs That Have Been Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                                                                                                                                                                                                                                                                      | 13              |  | 14 |  | 13 |  |
|                                                                                                                                                                                                                                                                                                                                                                                                                                  |
| [1]The 2013 amount relates primarily to Gunflint (deepwater Gulf of Mexico), for which we sanctioned a development plan.[2]The 2012 amount primarily represents Deep Blue (deepwater Gulf of Mexico) exploratory well costs capitalized prior to December 31, 2012.[3]The 2012 amount relates to Selkirk (North Sea) exploratory well costs capitalized prior to December 31, 2012. See Note 3. Property Transactions. |

| X                                                                                                                                                                                                                                                                |
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| - Definition
Capitalized Exploratory Well Cost, Other
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Additions to capitalized exploratory well costs that were added during the reporting period pending the determination of proved reserves.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 1B -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=8451039&loc=SL6806780-109447
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
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| - Definition
Capitalized exploratory well costs that were expensed during the year because proved reserves were not found at the exploratory well.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 1B -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=8451039&loc=SL6806780-109447
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount of capitalized exploratory well costs that is pending the determination of proved reserves. This does not include amounts that were capitalized and subsequently expensed in the same annual period.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 1B -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=8451039&loc=SL6806780-109447
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount of exploratory well costs that have been capitalized for a period of greater than one year after the completion of drilling.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 1B -Subparagraph b -URI http://asc.fasb.org/extlink&oid=8451039&loc=SL6806780-109447
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount of exploratory well costs that have been capitalized for a period of one year or less after the completion of drilling.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 16 -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e61939-109447
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The number of projects for which exploratory well costs have been capitalized for a period of greater than one year after the completion of drilling.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 1B -Subparagraph b -URI http://asc.fasb.org/extlink&oid=8451039&loc=SL6806780-109447
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
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| - Definition
Previously capitalized costs of the drilling of wells that were reclassified as part of the costs of the enterprise's wells and related equipment and facilities at the time that proved reserves were found.
+ References
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