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		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income (loss) from Australian discontinued operations, net of tax		$ 0	$ 120	$ 0	$ (118)
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			101		288
Income from divested Australian operations			18		28
Income tax benefit			(241)		(42)
Income (loss) from Australian discontinued operations, net of tax			120		(118)
Woodside Sale [Member] | Australia [Member] | Divestiture [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on disposal					(49)
Consortium Sale [Member] | Australia [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on disposal	$ 139
Consortium Sale [Member] | Australia [Member] | Divestiture [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on disposal			$ (139)		$ (139)