The adjustment to expense previously capitalized costs of drilling exploratory wells when proved reserves are not found or when the entity obtains information that raises substantial doubt about the economic or operational viability of the project.

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Name:	us-gaap_ExplorationAbandonmentAndImpairmentExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Impairments - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Property, Plant, and Equipment [Line Items]
Impairments	$ 0	$ 128	$ 0	$ 147
Impairment of unproved properties			41	149
Unproved Gulf of Mexico Properties [Member]
Property, Plant, and Equipment [Line Items]
Impairment of unproved properties			$ 35	$ 94
WES Midstream [Member]
Property, Plant, and Equipment [Line Items]
Impairments		$ 128