| **Segment Information - Assets and Goodwill by Segment (Details) - USD ($) $ in Millions** | Sep. 30, 2018 | Mar. 31, 2018 | Dec. 31, 2017 | Apr. 24, 2017 |
|--------------------------------------------------------------------------------------------|---------------|---------------|---------------|---------------|
| **Segment Reporting Information [Line Items]**                                             |          |          |          |          |
| Goodwill                                                                                   | $ 1,401       |          | $ 1,310       | $ 1,291       |
| Assets, net of AHFS                                                                        | 22,147        |          | 21,476        |          |
| Operating Segments | Eastern Mediterranean                                                 |          |          |          |          |
| **Segment Reporting Information [Line Items]**                                             |          |          |          |          |
| Goodwill                                                                                   | 0             |          | 0             |          |
| Assets, net of AHFS                                                                        | 3,184         |          | 2,846         |          |
| Operating Segments | West Africa                                                           |          |          |          |          |
| **Segment Reporting Information [Line Items]**                                             |          |          |          |          |
| Goodwill                                                                                   | 0             |          | 0             |          |
| Assets, net of AHFS                                                                        | 1,208         |          | 1,308         |          |
| Operating Segments | Other Int'l                                                           |          |          |          |          |
| **Segment Reporting Information [Line Items]**                                             |          |          |          |          |
| Goodwill                                                                                   | 0             |          | 0             |          |
| Assets, net of AHFS                                                                        | 66            |          | 114           |          |
| Operating Segments | United States                                                         |          |          |          |          |
| **Segment Reporting Information [Line Items]**                                             |          |          |          |          |
| Goodwill                                                                                   | 1,291         |          | 1,310         |          |
| Assets, net of AHFS                                                                        | 15,440        |          | 15,767        |          |
| Noble Midstream | United States                                                            |          |          |          |          |
| **Segment Reporting Information [Line Items]**                                             |          |          |          |          |
| Goodwill                                                                                   | 110           |          | 0             |          |
| Assets, net of AHFS                                                                        | 2,318         |          | 1,357         |          |
| Intersegment Eliminations                                                                  |          |          |          |          |
| **Segment Reporting Information [Line Items]**                                             |          |          |          |          |
| Goodwill                                                                                   | 0             |          | 0             |          |
| Assets, net of AHFS                                                                        | (150)         |          | (163)         |          |
| Corporate                                                                                  |          |          |          |          |
| **Segment Reporting Information [Line Items]**                                             |          |          |          |          |
| Goodwill                                                                                   | 0             |          | 0             |          |
| Assets, net of AHFS                                                                        | 81            |          | $ 247         |          |
| Saddle Butte                                                                               |          |          |          |          |
| **Segment Reporting Information [Line Items]**                                             |          |          |          |          |
| Goodwill                                                                                   | $ 110         |          |          |          |
| Intangible assets acquired                                                                 |          | $ 318         |          |          |

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| - Definition
Sum of carrying amounts as of balance sheet date of all assets (with the exception of assets that are held for sale) that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or results.
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| - Definition
Amount of intangible assets, excluding goodwill, acquired at the acquisition date.
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| - Definition
Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.
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