Segment Information - Reconciliation of Consolidated Adjusted EBITDAX to Income (Loss) before Income Taxes Table (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011	Sep. 30, 2012		Sep. 30, 2011
Reconciliation of Consolidated Adjusted EBITDAX to Income (Loss) before Income Taxes [Abstract]
Income (loss) before income taxes	$ 390		$ (4,496)	$ 3,019		$ (2,991)
Exploration expense	297		307	1,662		722
DD&A	979		932	2,936		2,902
Impairments	4		183	166		287
Deepwater Horizon settlement and related costs	4		4,042	15		4,077
Algeria exceptional profits tax settlement	7	[1]		(1,797)	[1]
Interest expense	185		206	561		642
Unrealized (gains) losses on derivatives, net	456		692	539		767
Segment Reporting Information [Line Items]
Realized (gains) losses on other derivatives, net	(197)		(70)	(598)		(136)
Less: Net income attributable to noncontrolling interests	21		23	67		62
Consolidated Adjusted EBITDAX	2,301		1,843	6,786		6,346
(Gains) Losses on Other Derivatives, net [Member] | Interest Rate Contract and Other [Member]
Reconciliation of Consolidated Adjusted EBITDAX to Income (Loss) before Income Taxes [Abstract]
Unrealized (gains) losses on derivatives, net	14		854	152		937
Segment Reporting Information [Line Items]
Realized (gains) losses on other derivatives, net				2	[1]	2	[1]
Tronox Litigation [Member]
Segment Reporting Information [Line Items]
Tronox-related contingent loss				$ (250)	[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.