Segment Information (Details) (USD $) In Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010		Dec. 31, 2010
Segment Reporting Information [Line Items]
Revenues from Third Parties	$ 874	$ 726		$ 2,632		$ 2,169
Reclassification from AOCL		(5)	[1]			(15)	[1]
Income from Equity Method Investees	50	34		146		85
Total	924	755		2,778		2,239
DD&A	225	231		681		662
Gain on Divestitures	0	(114)	[2]	(26)	[2]	(114)	[2]
Asset Impairments	0	100	[3]	139	[3]	100	[3]
(Gain) Loss on Commodity Derivative Instruments	(322)	(38)		(179)		(280)
Income (Loss) Before Income Taxes	722	298		1,185		962
Goodwill	696			696				696
Total Assets	15,833			15,833				13,282
United States [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	520	458		1,578		1,425
Reclassification from AOCL		(5)	[1]			(15)	[1]
Income from Equity Method Investees	0	0		0		0
Total	520	453		1,578		1,410
DD&A	180	184		534		543
Gain on Divestitures		(114)	[2]	(1)	[2]	(114)	[2]
Asset Impairments		100	[3]	137	[3]	100	[3]
(Gain) Loss on Commodity Derivative Instruments	(213)	(49)		(163)		(277)
Income (Loss) Before Income Taxes	418	211		631		681
Goodwill	696			696				696
Total Assets	10,921			10,921				9,091
West Africa [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	153	64		401		243
Reclassification from AOCL		0	[1]			0	[1]
Income from Equity Method Investees	50	34		146		85
Total	203	98		547		328
DD&A	13	10		30		28
Gain on Divestitures		0	[2]	0	[2]	0	[2]
Asset Impairments		0	[3]	0	[3]	0	[3]
(Gain) Loss on Commodity Derivative Instruments	(109)	11		(16)		(3)
Income (Loss) Before Income Taxes	270	64		460		258
Goodwill	0			0				0
Total Assets	2,544			2,544				2,270
Eastern Mediterranean [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	108	63		236		144
Reclassification from AOCL		0	[1]			0	[1]
Income from Equity Method Investees	0	0		0		0
Total	108	63		236		144
DD&A	8	7		19		18
Gain on Divestitures		0	[2]	0	[2]	0	[2]
Asset Impairments		0	[3]	0	[3]	0	[3]
(Gain) Loss on Commodity Derivative Instruments	0	0		0		0
Income (Loss) Before Income Taxes	88	51		184		110
Goodwill	0			0				0
Total Assets	1,540			1,540				919
North Sea [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	45	99		271		227
Reclassification from AOCL		0	[1]			0	[1]
Income from Equity Method Investees	0	0		0		0
Total	45	99		271		227
DD&A	10	20		62		45
Gain on Divestitures		0	[2]	0	[2]	0	[2]
Asset Impairments		0	[3]	2	[3]	0	[3]
(Gain) Loss on Commodity Derivative Instruments	0	0		0		0
Income (Loss) Before Income Taxes	23	59		161		132
Goodwill	0			0				0
Total Assets	625			625				770
Other International And Corporate [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	48	42		146		130
Reclassification from AOCL		0	[1]			0	[1]
Income from Equity Method Investees	0	0		0		0
Total	48	42		146		130
DD&A	14	10		36		28
Gain on Divestitures		0	[2]	(25)	[2]	0	[2]
Asset Impairments		0	[3]	0	[3]	0	[3]
(Gain) Loss on Commodity Derivative Instruments	0	0		0		0
Income (Loss) Before Income Taxes	(77)	(87)		(251)		(219)
Goodwill	0			0				0
Total Assets	$ 203			$ 203				$ 232

[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] See Note 3. Acquisitions and Divestitures.

[3] See Note 4. Asset Impairments.