Suspended Exploratory Well Costs - Aging of Suspended Well Balances (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Exploratory Well Costs Associated with Wells Suspended for a Period Greater Than One Year [Abstract]
Exploratory well costs capitalized for a period of one year or less	$ 152	$ 201	$ 460
Exploratory well costs capitalized for a period greater than one year	292	324	770
Balance at December 31	$ 444	$ 525	$ 1,230	$ 1,124

Exploratory Well Costs Associated with Wells Suspended for a Period Greater Than One Year [Abstract]

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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Namespace Prefix:	us-gaap_
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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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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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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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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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