| **Capitalized Exploratory Well Costs and Undeveloped Leasehold Costs - Aging of Exploratory Well Costs (Details) - USD ($) $ in Millions** | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 |
|--------------------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|---------------|
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | $ 348         | $ 510         | $ 699         |
| Felicita (Block O)                                                                                                                         |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | 48            |          |          |
| Yolanda (Block I)                                                                                                                          |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | 24            |          |          |
| YoYo (YoYo Block)                                                                                                                          |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | 52            |          |          |
| Leviathan-1 Deep                                                                                                                           |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | 94            |          |          |
| Dalit                                                                                                                                      |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | 24            |          |          |
| Cyprus                                                                                                                                     |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | 100           |          |          |
| Projects less than $20 million                                                                                                             |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | 6             |          |          |
| Suspended Since 2016 and 2017                                                                                                              |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | 16            |          |          |
| Suspended Since 2016 and 2017 | Felicita (Block O)                                                                                         |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | 3             |          |          |
| Suspended Since 2016 and 2017 | Yolanda (Block I)                                                                                          |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | 2             |          |          |
| Suspended Since 2016 and 2017 | YoYo (YoYo Block)                                                                                          |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | (1)           |          |          |
| Suspended Since 2016 and 2017 | Leviathan-1 Deep                                                                                           |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | 6             |          |          |
| Suspended Since 2016 and 2017 | Dalit                                                                                                      |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | 2             |          |          |
| Suspended Since 2016 and 2017 | Cyprus                                                                                                     |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | 11            |          |          |
| Suspended Since 2016 and 2017 | Projects less than $20 million                                                                             |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | (7)           |          |          |
| Suspended Since 2014 and 2015                                                                                                              |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | 49            |          |          |
| Suspended Since 2014 and 2015 | Felicita (Block O)                                                                                         |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | 7             |          |          |
| Suspended Since 2014 and 2015 | Yolanda (Block I)                                                                                          |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | 3             |          |          |
| Suspended Since 2014 and 2015 | YoYo (YoYo Block)                                                                                          |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | 6             |          |          |
| Suspended Since 2014 and 2015 | Leviathan-1 Deep                                                                                           |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | 8             |          |          |
| Suspended Since 2014 and 2015 | Dalit                                                                                                      |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | 3             |          |          |
| Suspended Since 2014 and 2015 | Cyprus                                                                                                     |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | 12            |          |          |
| Suspended Since 2014 and 2015 | Projects less than $20 million                                                                             |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | 10            |          |          |
| Suspended Since 2013 and Prior                                                                                                             |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | 283           |          |          |
| Suspended Since 2013 and Prior | Felicita (Block O)                                                                                        |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | 38            |          |          |
| Suspended Since 2013 and Prior | Yolanda (Block I)                                                                                         |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | 19            |          |          |
| Suspended Since 2013 and Prior | YoYo (YoYo Block)                                                                                         |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | 47            |          |          |
| Suspended Since 2013 and Prior | Leviathan-1 Deep                                                                                          |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | 80            |          |          |
| Suspended Since 2013 and Prior | Dalit                                                                                                     |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | 19            |          |          |
| Suspended Since 2013 and Prior | Cyprus                                                                                                    |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | 77            |          |          |
| Suspended Since 2013 and Prior | Projects less than $20 million                                                                            |          |          |          |
| **Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]**                                                   |          |          |          |
| Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling                                       | $ 3           |          |          |

| 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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 1B -Subparagraph b -URI http://asc.fasb.org/extlink&oid=68064819&loc=SL6806780-109447
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| - Definition
Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.
+ References
No definition available.
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