Segment Information - Reconciliation of Consolidated Adjusted EBITDAX to Income (Loss) before Income Taxes Table (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Reconciliation of Consolidated Adjusted EBITDAX to Income (Loss) before Income Taxes [Abstract]
Income (loss) before income taxes	$ 3,565		$ (3,424)		$ 1,641
Exploration expense	1,946		1,076		974
DD&A	3,964		3,830		3,714
Impairments	389		1,774		216
Deepwater Horizon settlement and related costs	18		3,930		15
Algeria exceptional profits tax settlement	(1,797)	[1]
Segment Reporting Information [Line Items]
Unrealized (gains) losses on derivatives, net	377		616		(114)
Interest expense	742		839		855
Less net income attributable to noncontrolling interests	54		81		60
Consolidated Adjusted EBITDAX	8,966		8,869		7,146
(Gains) Losses on Derivatives, net [Member] | Interest-Rate and Other Derivatives [Member]
Segment Reporting Information [Line Items]
Unrealized (gains) losses on derivatives, net	(5)		964		285
Realized (gains) losses on other derivatives, net	66	[1]	59	[1]
Gathering, Processing, and Marketing Sales and Gains (Losses) on Derivatives, Net [Member]
Segment Reporting Information [Line Items]
Unrealized (gains) losses on derivatives, net	377		616		(114)
Realized (gains) losses on other derivatives, net	(685)		(147)		(495)
Tronox Litigation [Member]
Segment Reporting Information [Line Items]
Tronox-related contingent loss	$ (250)	[1]	$ 250	[1]	$ (95)	[1]

[1] In the first quarter of 2012, the Company revised the definition of Adjusted EBITDAX to exclude Algeria exceptional profits tax settlement, Tronox-related contingent loss, and realized (gains) losses on other derivatives, net. Prior periods have been adjusted to reflect this change.