Acquisitions and Divestitures - Additional Information - 2014 Activity - Gulf of Mexico Deepwater Divestiture (Detail) - USD ($) $ in Millions		1 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale of 11 primary-term deepwater exploration blocks		$ 1,200	$ 268	$ 470	$ 307
Deepwater Gulf of Mexico [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale of 11 primary-term deepwater exploration blocks	$ 1,400
Effective date of sale	May 01, 2014
Decrease in net book value of proved oil and gas properties	$ (850)
Decrease in net book value of unproved oil and gas properties	$ (518)