Segment Information - Reconciliation of Consolidated Adjusted EBITDAX to Income (Loss) before Income Taxes Table (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Reconciliation of Consolidated Adjusted EBITDAX to Income (Loss) before Income Taxes [Abstract]
Income (loss) before income taxes	$ 94		$ 1,002		$ 2,629		$ 1,505
Exploration expense	1,121		236		1,365		415
DD&A	1,027		985		1,957		1,970
Impairments	112		102		162		104
Deepwater Horizon settlement and related costs	3	[1]	9	[1]	11	[1]	35	[1]
Algeria exceptional profits tax settlement					(1,804)	[2]
Interest expense	190		216		376		436
Segment Reporting Information [Line Items]
Unrealized (gains) losses on derivatives, net					83		75
Less: Net income attributable to noncontrolling interests	19		18		46		39
Consolidated Adjusted EBITDAX	2,230		2,356		4,485		4,503
Tronox Litigation [Member]
Segment Reporting Information [Line Items]
Tronox-related contingent loss	(525)	[2]			(250)	[2]
Nondesignated [Member]
Segment Reporting Information [Line Items]
Unrealized (gains) losses on derivatives, net	225		(178)		83		75
Realized (gains) losses on derivatives, net	(262)		(21)		(401)		(66)
Nondesignated [Member] | (Gains) Losses on Other Derivatives, net [Member] | Interest Rate Contract and Other [Member]
Segment Reporting Information [Line Items]
Unrealized (gains) losses on derivatives, net	374		142		138		83
Realized (gains) losses on derivatives, net	$ 2	[2]	$ 2	[2]	$ 2	[2]	$ 2	[2]

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

[2] 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.