| **Acquisitions and Divestitures - Consideration Transferred and Purchase Price Allocation (Details) - USD ($) $ in Millions** | Apr. 24, 2017 | Mar. 31, 2018 | Dec. 31, 2017 |
|-------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|---------------|
| **Business Acquisition [Line Items]**                                                                                         |          |          |          |
| Fair Value of Common Stock Issued                                                                                             | $ 1,851       |          |          |
| Plus: Cash Consideration Paid to Clayton Williams Energy Stockholders                                                         | 637           |          |          |
| Total Purchase Price                                                                                                          | 2,488         |          |          |
| **Plus Liabilities Assumed by Noble Energy:**                                                                                 |          |          |          |
| Accounts Payable                                                                                                              | 99            |          |          |
| Other Current Liabilities                                                                                                     | 38            |          |          |
| Long-Term Deferred Tax Liability                                                                                              | 515           |          |          |
| Long-Term Debt                                                                                                                | 595           |          |          |
| Asset Retirement Obligations                                                                                                  | 63            |          |          |
| Total Purchase Price Plus Liabilities Assumed                                                                                 | 3,798         |          |          |
| Cash and Cash Equivalents                                                                                                     | 21            |          |          |
| Other Current Assets                                                                                                          | 70            |          |          |
| **Oil and Gas Properties:**                                                                                                   |          |          |          |
| Proved Reserves                                                                                                               | 722           |          |          |
| Undeveloped Leasehold Costs                                                                                                   | 1,571         |          |          |
| Gathering and Processing Assets                                                                                               | 48            |          |          |
| Asset Retirement Costs                                                                                                        | 63            |          |          |
| Other Noncurrent Assets                                                                                                       | 12            |          |          |
| Goodwill                                                                                                                      | 1,291         | $ 1,402       | $ 1,310       |
| Total Asset Value                                                                                                             | $ 3,798       |          |          |

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Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.
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Amount of equity interests of the acquirer, including instruments or interests issued or issuable in consideration for the business combination.
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Amount recognized as of the acquisition date for the identifiable assets acquired in excess of (less than) the aggregate liabilities assumed.
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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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