Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011		Dec. 31, 2011
Segment Reporting Information [Line Items]
Revenues from Third Parties	$ 934		$ 794		$ 1,970		$ 1,533
Income from Equity Method Investees	32		48		86		96
Total Revenues	966		842		2,056		1,629
Depreciation, Depletion and Amortization	325		211		619		404
Asset Impairments	73	[1]	131	[1]	73	[1]	137	[1]
Gain on Divestitures	(9)		(25)	[2]	(9)		(26)	[2]
(Gain) Loss on Commodity Derivative Instruments	(276)	[3]	(143)	[3]	(180)		143	[3]
Income from Continuing Operations Before Income Taxes	390		356		724		325
Goodwill	696				696				696
Total Assets	16,657				16,657				16,106
United States [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	527		553		1,080		1,059
Income from Equity Method Investees	1		0		3		0
Total Revenues	528		553		1,083		1,059
Depreciation, Depletion and Amortization	232		187		430		354
Asset Impairments	73	[1]	131	[1]	73	[1]	137	[1]
Gain on Divestitures	(9)		0	[2]	(9)		(1)	[2]
(Gain) Loss on Commodity Derivative Instruments	(93)	[3]	(142)	[3]	(102)		50	[3]
Income from Continuing Operations Before Income Taxes	48		250		241		213
Goodwill	696				696				696
Total Assets	11,188				11,188				11,201
West Africa [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	332		118		715		248
Income from Equity Method Investees	31		48		83		96
Total Revenues	363		166		798		344
Depreciation, Depletion and Amortization	62		7		135		17
Asset Impairments	0	[1]	0	[1]	0	[1]	0	[1]
Gain on Divestitures	0		0	[2]	0		0	[2]
(Gain) Loss on Commodity Derivative Instruments	(183)	[3]	(1)	[3]	(78)		93	[3]
Income from Continuing Operations Before Income Taxes	455		116		682		190
Goodwill	0				0				0
Total Assets	2,761				2,761				2,728
Eastern Mediterranean [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	29		76		73		128
Income from Equity Method Investees	0		0		0		0
Total Revenues	29		76		73		128
Depreciation, Depletion and Amortization	10		7		15		11
Asset Impairments	0	[1]	0	[1]	0	[1]	0	[1]
Gain on Divestitures	0		0	[2]	0		0	[2]
(Gain) Loss on Commodity Derivative Instruments	0	[3]	0	[3]	0		0	[3]
Income from Continuing Operations Before Income Taxes	5		57		37		96
Goodwill	0				0				0
Total Assets	2,289				2,289				1,751
Other International And Corporate [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	46		47		102		98
Income from Equity Method Investees	0		0		0		0
Total Revenues	46		47		102		98
Depreciation, Depletion and Amortization	21		10		39		22
Asset Impairments	0	[1]	0	[1]	0	[1]	0	[1]
Gain on Divestitures	0		(25)	[2]	0		(25)	[2]
(Gain) Loss on Commodity Derivative Instruments	0	[3]	0	[3]	0		0	[3]
Income from Continuing Operations Before Income Taxes	(118)		(67)		(236)		(174)
Goodwill	0				0				0
Total Assets	$ 419				$ 419				$ 426

[1] See Note 4. Asset Impairments.

[2] Amount relates primarily to the transfer of our Ecuador assets to the Ecuadorian government. See Note 2. Basis of Presentation.

[3] See Note 6. Derivative Instruments and Hedging Activities.