Reconciliation of Consolidated Adjusted EBITDAX to Income (Loss) before Income Taxes Table (Detail) (USD $) In Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
Reconciliation of Consolidated Adjusted EBITDAX to Income (Loss) before Income Taxes [Abstract]
Income (loss) before income taxes	$ (4,496)		$ 86		$ (2,991)		$ 1,352
Exploration expense	307		296		722		649
DD&A	932		962		2,902		2,845
Impairments	183		20		287		147
Deepwater Horizon settlement and related costs	4,042	[1]	2	[1]	4,055	[1]	2	[1]
Interest expense	206		218		642		642
Segment Reporting Information [Line Items]
Unrealized (gains) losses on derivatives, net					767		(66)
Less: Net income attributable to noncontrolling interests	23		18		62		42
Consolidated Adjusted EBITDAX	1,843		1,740		6,322		5,529
Nondesignated [Member]
Segment Reporting Information [Line Items]
Unrealized (gains) losses on derivatives, net	$ 692	[2]	$ 174	[2]	$ 767	[2]	$ (66)	[2]

[1] In the third quarter of 2011, the Company revised the definition of Adjusted EBITDAX to exclude the Deepwater Horizon settlement and related costs. The prior periods have been adjusted to reflect this change.

[2] In the fourth quarter of 2010, the Company revised the definition of Adjusted EBITDAX to exclude the impact of unrealized (gains) losses on derivative instruments, net. The prior periods have been adjusted to reflect this change.