Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=109226348&loc=d3e2420-110228

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

Dispositions - Schedule of Pre-tax Income (Loss) Associated with Interests Excluding Financial Statement Impacts Resulting from Asset Sales (Parenthetical) (Detail) - USD ($) $ in Millions	1 Months Ended		12 Months Ended
	Dec. 31, 2017	Nov. 30, 2017	Dec. 31, 2017
Disposition Of Businesses [Line Items]
Pre-tax impairment charge			$ 4,203
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Equatorial Guinea
Disposition Of Businesses [Line Items]
Gains (loss) on sales of assets		$ 486
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Norway
Disposition Of Businesses [Line Items]
Gains (loss) on sales of assets	$ (857)
Pre-tax impairment charge			$ 2,503