Dispositions (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from asset sales	$ 493	$ 22	$ 607
Gain (loss) on asset sales, pre-tax	$ 87	22	32
Shenzi Field
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Project interest percentage	28.00%
Proceeds from asset sales	$ 482
Gain (loss) on asset sales, pre-tax	79
Gain (loss) on asset sale, after income taxes	$ 79
Ghana
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from asset sales			25
Gain (loss) on asset sales, pre-tax			10
Gain (loss) on asset sale, after income taxes			10
Agreement entered to sell interest, total consideration			100
Further payment consideration			75
Utica Shale Play | Eastern Ohio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from asset sales		22	396
Gain (loss) on asset sales, pre-tax		22	14
Gain (loss) on asset sale, after income taxes		$ 22	$ 14