Exploratory Well Costs (Capitalized Exploratory Well Activity) (Detail) $ in Millions	9 Months Ended
Sep. 30, 2017 USD ($)
Disclosure Exploratory Well Costs Capitalized Exploratory Well Activity [Abstract]
Beginning capitalized exploratory well costs	$ 151
Additions to exploratory well costs pending the determination of proved reserves	255
Reclassifications due to determination of proved reserves	(136)
Ending capitalized exploratory well costs	$ 270

Disclosure - Exploratory Well Costs (Capitalized Exploratory Well Activity) [Abstract]

No definition available.

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- Definition

Additions to capitalized exploratory well costs that were added during the reporting period pending the determination of proved reserves.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 235
-Section 50
-Paragraph 1B
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=68064819&loc=SL6806780-109447

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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://www.xbrl.org/2003/role/presentationRef
-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

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- Definition

Previously capitalized costs of the drilling of wells that were reclassified as part of the costs of the enterprise's wells and related equipment and facilities at the time that proved reserves were found.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 235
-Section 50
-Paragraph 1B
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=68064819&loc=SL6806780-109447

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