Asset Retirement Obligations - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Reclassified Liabilities	$ 227	$ 0
Liabilities Settled	20	9
Revisions of estimates	11	$ 7
Gulf of Mexico Assets \| Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Reclassified Liabilities	227
Liabilities Settled	20
Revisions of estimates	$ 11

Asset Retirement Obligation, Transferred

No definition available.

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- Definition

Amount of asset retirement obligations settled, or otherwise disposed of, during the period. This may include asset retirement obligations transferred to third parties associated with the sale of a long-lived asset.

+ References

+ Details

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- Definition

Amount of increase (decrease) in the asset retirement obligation from changes in the amount or timing of the estimated cash flows associated with the settlement of the obligation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)(4)
-URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 35
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6392603&loc=d3e7123-110846

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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.

+ Details

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