| **Commitments and Contingencies (Details) (USD $)In Millions, unless otherwise specified**                                     | 12 Months Ended |
|--------------------------------------------------------------------------------------------------------------------------------|-----------------|
||
| **Significant Purchase And Supply Commitments [Line Items]**                                                                   |            |  |   |   |
| Rental Expense for office buildings and oil and gas operations equipment                                                       | $ 37            |  | $ 31 | $ 27 |
| 2013                                                                                                                           | 939             |  |   |   |
| 2014                                                                                                                           | 383             |  |   |   |
| 2015                                                                                                                           | 383             |  |   |   |
| 2016                                                                                                                           | 286             |  |   |   |
| 2017                                                                                                                           | 180             |  |   |   |
| 2018 and Thereafter                                                                                                            | 722             |  |   |   |
| Total                                                                                                                          | 2,893           |  |   |   |
| Drilling, Equipment, and Purchase Obligations [Member]                                                                         |            |  |   |   |
| **Significant Purchase And Supply Commitments [Line Items]**                                                                   |            |  |   |   |
| 2013                                                                                                                           | 739             |  |   |   |
| 2014                                                                                                                           | 191             |  |   |   |
| 2015                                                                                                                           | 175             |  |   |   |
| 2016                                                                                                                           | 101             |  |   |   |
| 2017                                                                                                                           | 0               |  |   |   |
| 2018 and Thereafter                                                                                                            | 0               |  |   |   |
| Total                                                                                                                          | 1,206           |  |   |   |
| Transportation and Gathering [Member]                                                                                          |            |  |   |   |
| **Significant Purchase And Supply Commitments [Line Items]**                                                                   |            |  |   |   |
| 2013                                                                                                                           | 81              |  |   |   |
| 2014                                                                                                                           | 78              |  |   |   |
| 2015                                                                                                                           | 86              |  |   |   |
| 2016                                                                                                                           | 88              |  |   |   |
| 2017                                                                                                                           | 87              |  |   |   |
| 2018 and Thereafter                                                                                                            | 311             |  |   |   |
| Total                                                                                                                          | 731             |  |   |   |
| Operating Lease Obligations [Member]                                                                                           |            |  |   |   |
| **Significant Purchase And Supply Commitments [Line Items]**                                                                   |            |  |   |   |
| 2013                                                                                                                           | 47              |  |   |   |
| 2014                                                                                                                           | 42              |  |   |   |
| 2015                                                                                                                           | 52              |  |   |   |
| 2016                                                                                                                           | 52              |  |   |   |
| 2017                                                                                                                           | 48              |  |   |   |
| 2018 and Thereafter                                                                                                            | 302             |  |   |   |
| Total                                                                                                                          | 543             |  |   |   |
| FPSO Lease Obligation [Member]                                                                                                 |            |  |   |   |
| **Significant Purchase And Supply Commitments [Line Items]**                                                                   |            |  |   |   |
| 2013                                                                                                                           | 72              | [1] |   |   |
| 2014                                                                                                                           | 72              | [1] |   |   |
| 2015                                                                                                                           | 70              | [1] |   |   |
| 2016                                                                                                                           | 45              | [1] |   |   |
| 2017                                                                                                                           | 45              | [1] |   |   |
| 2018 and Thereafter                                                                                                            | 109             | [1] |   |   |
| Total                                                                                                                          | $ 413           | [1] |   |   |
|                                                                                                                                |
| [1]Annual lease payments, net to our interest, exclude regular maintenance and operational costs. See Note 12. Long-Term Debt. |

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| - Definition
Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41499-112717
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Minimum amount of other commitment not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in the taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Minimum amount of other commitment maturing after the fifth fiscal year following the latest fiscal year for commitments not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in this taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.
+ References
No definition available.
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Minimum amount of other commitment maturing in the fifth fiscal year following the latest fiscal year for commitments not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in this taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.
+ References
No definition available.
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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Minimum amount of other commitment maturing in the fourth fiscal year following the latest fiscal year for commitments not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in this taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Minimum amount of other commitment maturing in the next fiscal year following the latest fiscal year for commitments not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in this taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.
+ References
No definition available.
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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Minimum amount of other commitment maturing in the second fiscal year following the latest fiscal year for commitments not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in this taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.
+ References
No definition available.
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Minimum amount of other commitment maturing in the third fiscal year following the latest fiscal year for commitments not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in this taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.
+ References
No definition available.
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