Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011		Dec. 31, 2011
Segment Reporting Information [Line Items]
Revenues from Third Parties	$ 955		$ 829		$ 2,925		$ 2,361
Income from Equity Method Investees	51		50		137		146
Total Revenues	1,006		879		3,062		2,507
Depreciation, Depletion and Amortization	368		215		987		619
Gain on Divestitures	(157)	[1]	0		(167)	[1]	(26)	[1]
Asset Impairments	0		0		73	[2]	137	[2]
(Gain) Loss on Commodity Derivative Instruments	135	[3]	(322)	[3]	(46)	[3]	(179)	[3]
Income from Continuing Operations Before Income Taxes	275		699		999		1,024
Goodwill	635				635				696
Total Assets	16,787				16,787				16,106
United States [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	594		520		1,674		1,578
Income from Equity Method Investees	3		0		6		0
Total Revenues	597		520		1,680		1,578
Depreciation, Depletion and Amortization	240		180		670		534
Gain on Divestitures	(157)	[1]			(167)	[1]	(1)	[1]
Asset Impairments					73	[2]	137	[2]
(Gain) Loss on Commodity Derivative Instruments	42	[3]	(213)	[3]	(60)	[3]	(163)	[3]
Income from Continuing Operations Before Income Taxes	337		418		578		631
Goodwill	635				635				696
Total Assets	11,014				11,014				11,201
West Africa [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	280		153		995		401
Income from Equity Method Investees	48		50		131		146
Total Revenues	328		203		1,126		547
Depreciation, Depletion and Amortization	61		13		196		30
Gain on Divestitures	0	[1]			0	[1]	0	[1]
Asset Impairments					0	[2]	0	[2]
(Gain) Loss on Commodity Derivative Instruments	93	[3]	(109)	[3]	14	[3]	(16)	[3]
Income from Continuing Operations Before Income Taxes	85		270		767		460
Goodwill	0				0				0
Total Assets	2,782				2,782				2,728
Eastern Mediterranean [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	48		108		121		236
Income from Equity Method Investees	0		0		0		0
Total Revenues	48		108		121		236
Depreciation, Depletion and Amortization	49		8		64		19
Gain on Divestitures	0	[1]			0	[1]	0	[1]
Asset Impairments					0	[2]	0	[2]
(Gain) Loss on Commodity Derivative Instruments	0	[3]	0	[3]	0	[3]	0	[3]
Income from Continuing Operations Before Income Taxes	(11)		88		26		184
Goodwill	0				0				0
Total Assets	2,443				2,443				1,751
Other International And Corporate [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	33		48		135		146
Income from Equity Method Investees	0		0		0		0
Total Revenues	33		48		135		146
Depreciation, Depletion and Amortization	18		14		57		36
Gain on Divestitures	0	[1]			0	[1]	(25)	[1]
Asset Impairments					0	[2]	0	[2]
(Gain) Loss on Commodity Derivative Instruments	0	[3]	0	[3]	0	[3]	0	[3]
Income from Continuing Operations Before Income Taxes	(136)		(77)		(372)		(251)
Goodwill	0				0				0
Total Assets	$ 548				$ 548				$ 426

[1] See Note 3. Acquisitions and Divestitures.

[2] See Note 4. Asset Impairments.

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