Acquisitions and Divestitures - Summary of Sales and Other Operating Revenue and Loss From Discontinued Operation Related to Disposition - Australia Divestitures (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended								12 Months Ended
	Jun. 30, 2015	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015		Dec. 31, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on sale	$ 139
Income (loss) from discontinued operations, net of tax		$ 0	$ (33)	$ 0	$ 0	$ 627	$ (17)	$ 120	$ (238)	$ (33)	$ 492	[1]	$ (1,707)	[1]
Australia [Member] | Divestiture [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues and other from discontinued operations										0	288		1,050
Income (loss) from divested Australian operations										0	28		(12)
Income tax benefit (expense)										0	652		(231)
Income (loss) from discontinued operations, net of tax										(23)	492		(1,076)
Australia [Member] | Divestiture [Member] | Woodside Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment on Woodside sale										0	(49)		(833)
Loss on sale										(23)	0		0
Australia [Member] | Divestiture [Member] | Consortium Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on sale										$ 0	$ (139)		$ 0

[1] Financial information for 2015 and 2014 has been recast to reflect retrospective application of the successful efforts method of accounting. See Note 1.