Capitalized Exploratory Well Costs and Undeveloped Leasehold Costs - Aging of Capitalized Exploratory Well Costs (Details) $ in Millions	Sep. 30, 2018 USD ($) project	Dec. 31, 2017 USD ($) project
Extractive Industries [Abstract]
Exploratory Well Costs Capitalized for a Period of One Year or Less	$ 8	$ 10
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	350	510
Balance at End of Period	$ 358	$ 520
Number of Projects with Exploratory Well Costs That Have Been Capitalized for a Period Greater Than One Year Since Commencement of Drilling \| project	7	8

No definition available.

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- Definition

The amount of capitalized exploratory well costs that is pending the determination of proved reserves. This does not include amounts that were capitalized and subsequently expensed in the same annual period.

+ 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 (a)
-URI http://asc.fasb.org/extlink&oid=68064819&loc=SL6806780-109447

+ Details

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- 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

+ Details

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- Definition

The amount of exploratory well costs that have been capitalized for a period of one year or less after the completion of drilling.

+ References

No definition available.

+ Details

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- Definition

The number of projects for which exploratory well costs 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

+ Details

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