Segment Information (Details) (USD $)	3 Months Ended				6 Months Ended
	Jun. 30, 2011		Jun. 30, 2010		Jun. 30, 2011		Jun. 30, 2010		Dec. 31, 2010
Segment Reporting Information [Line Items]
Revenues from Third Parties	$ 906,000,000		$ 731,000,000		$ 1,758,000,000		$ 1,444,000,000
Reclassification from AOCL			(4,000,000)	[1]			(10,000,000)	[1]
Income from Equity Method Investees	48,000,000		24,000,000		96,000,000		50,000,000
Total Revenues	954,000,000		751,000,000		1,854,000,000		1,484,000,000
DD&A	235,000,000		215,000,000		456,000,000		431,000,000
Asset Impairments	131,000,000		0		139,000,000		0
Gain on Divestitures	(25,000,000)	[2]	0	[2]	(26,000,000)	[2]	0	[2]
(Gain) Loss on Commodity Derivative Instruments	(143,000,000)		(96,000,000)		143,000,000		(242,000,000)
Income (Loss) Before Income Taxes	425,000,000		320,000,000		462,000,000		664,000,000
Goodwill	696,000,000				696,000,000				696,000,000
Total Assets	14,339,000,000				14,339,000,000				13,282,000,000
United States [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	553,000,000		459,000,000		1,058,000,000		968,000,000
Reclassification from AOCL			(4,000,000)	[1]			(10,000,000)	[1]
Income from Equity Method Investees	0		0		0		0
Total Revenues	553,000,000		455,000,000		1,058,000,000		958,000,000
DD&A	187,000,000		177,000,000		354,000,000		358,000,000
Asset Impairments	131,000,000				137,000,000
Gain on Divestitures	0	[2]			(1,000,000)	[2]
(Gain) Loss on Commodity Derivative Instruments	(142,000,000)		(81,000,000)		50,000,000		(227,000,000)
Income (Loss) Before Income Taxes	250,000,000		181,000,000		213,000,000		470,000,000
Goodwill	696,000,000				696,000,000				696,000,000
Total Assets	9,607,000,000				9,607,000,000				9,091,000,000
West Africa [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	118,000,000		118,000,000		248,000,000		179,000,000
Reclassification from AOCL			0	[1]			0	[1]
Income from Equity Method Investees	48,000,000		24,000,000		96,000,000		50,000,000
Total Revenues	166,000,000		142,000,000		344,000,000		229,000,000
DD&A	7,000,000		11,000,000		17,000,000		19,000,000
Asset Impairments	0				0
Gain on Divestitures	0	[2]			0	[2]
(Gain) Loss on Commodity Derivative Instruments	(1,000,000)		(15,000,000)		93,000,000		(15,000,000)
Income (Loss) Before Income Taxes	116,000,000		127,000,000		190,000,000		194,000,000
Goodwill	0				0				0
Total Assets	2,531,000,000				2,531,000,000				2,270,000,000
Eastern Mediterranean [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	76,000,000		48,000,000		128,000,000		81,000,000
Reclassification from AOCL			0	[1]			0	[1]
Income from Equity Method Investees	0		0		0		0
Total Revenues	76,000,000		48,000,000		128,000,000		81,000,000
DD&A	7,000,000		7,000,000		11,000,000		11,000,000
Asset Impairments	0				0
Gain on Divestitures	0	[2]			0	[2]
(Gain) Loss on Commodity Derivative Instruments	0		0		0		0
Income (Loss) Before Income Taxes	57,000,000		33,000,000		96,000,000		59,000,000
Goodwill	0				0				0
Total Assets	1,276,000,000				1,276,000,000				919,000,000
North Sea [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	112,000,000		62,000,000		226,000,000		128,000,000
Reclassification from AOCL			0	[1]			0	[1]
Income from Equity Method Investees	0		0		0		0
Total Revenues	112,000,000		62,000,000		226,000,000		128,000,000
DD&A	24,000,000		11,000,000		52,000,000		26,000,000
Asset Impairments	0				2,000,000
Gain on Divestitures	0	[2]			0	[2]
(Gain) Loss on Commodity Derivative Instruments	0		0		0		0
Income (Loss) Before Income Taxes	70,000,000		36,000,000		138,000,000		73,000,000
Goodwill	0				0				0
Total Assets	728,000,000				728,000,000				770,000,000
Other International And Corporate [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	47,000,000		44,000,000		98,000,000		88,000,000
Reclassification from AOCL			0	[1]			0	[1]
Income from Equity Method Investees	0		0		0		0
Total Revenues	47,000,000		44,000,000		98,000,000		88,000,000
DD&A	10,000,000		9,000,000		22,000,000		17,000,000
Asset Impairments	0				0
Gain on Divestitures	(25,000,000)	[2]			(25,000,000)	[2]
(Gain) Loss on Commodity Derivative Instruments	0		0		0		0
Income (Loss) Before Income Taxes	(68,000,000)		(57,000,000)		(175,000,000)		(132,000,000)
Goodwill	0				0				0
Total Assets	$ 197,000,000				$ 197,000,000				$ 232,000,000

[1] Revenues include decreases resulting from hedging activities. The decreases resulted from hedge gains and losses that were deferred in AOCL, as a result of previous cash flow hedge accounting, and subsequently reclassified to revenues. All hedge gains and losses had been reclassified to revenues by December 31, 2010.

[2] Amount relates primarily to the transfer of assets to the Ecuadorian government. We received cash proceeds of $73 million for the transfer of our offshore Amistad field assets and Block 3 production sharing contract (PSC), which was terminated by the government of Ecuador on November 25, 2010, and the assignment of the Machala Power Electricity concession and its associated assets. Our net book value for the assets had been reduced due to previous reductions for impairments, resulting in a gain of $26 million before tax. We did not consider the property disposition material for discontinued operations presentation.