Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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

Goodwill and Other Intangible Assets - Goodwill (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Line Items]
Goodwill	$ 4,789,000,000	$ 4,789,000,000	$ 5,000,000,000
Goodwill impairment loss	0
Exploration and Production [Member]
Goodwill [Line Items]
Goodwill	4,300,000,000
WES Midstream [Member]
Goodwill [Line Items]
Goodwill	$ 446,000,000