Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012		Dec. 31, 2012
Segment Reporting Information [Line Items]
Revenues from Third Parties	$ 1,341		$ 954		$ 3,537		$ 2,925
Income from Equity Method Investees	53		51		150		137
Total Revenues	1,394		1,005		3,687		3,062
DD&A	412		368		1,146		987
Gain on Divestitures	0		(157)		(12)		(167)
Asset Impairments	63		0		63		73
(Gain) Loss on Commodity Derivative Instruments	157	[1]	135	[1]	69	[1]	(46)	[1]
Income (Loss) from Continuing Operations Before Income Taxes	311		275		1,115		999
Total Assets	18,829				18,829				17,509
United States [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	810		593		2,209		1,674
Income from Equity Method Investees	0		3		0		6
Total Revenues	810		596		2,209		1,680
DD&A	295		240		819		670
Gain on Divestitures	0		(157)				(167)
Asset Impairments	16		0		16		73
(Gain) Loss on Commodity Derivative Instruments	115	[1]	42	[1]	54	[1]	(60)	[1]
Income (Loss) from Continuing Operations Before Income Taxes	183		337		746		578
Total Assets	12,462				12,462				11,199
West Africa [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	372		280		935		995
Income from Equity Method Investees	53		48		150		131
Total Revenues	425		328		1,085		1,126
DD&A	72		61		189		196
Gain on Divestitures	0		0		0		0
Asset Impairments	0		0		0		0
(Gain) Loss on Commodity Derivative Instruments	42	[1]	93	[1]	15	[1]	14	[1]
Income (Loss) from Continuing Operations Before Income Taxes	223		85		722		767
Total Assets	3,300				3,300				3,063
Eastern Mediterranean [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	122		48		274		121
Income from Equity Method Investees	0		0		0		0
Total Revenues	122		48		274		121
DD&A	26		49		81		64
Gain on Divestitures	0		0		0		0
Asset Impairments	47		0		47		0
(Gain) Loss on Commodity Derivative Instruments	0	[1]	0	[1]	0		0
Income (Loss) from Continuing Operations Before Income Taxes	34		(11)		93		26
Total Assets	2,642				2,642				2,572
Other Int'l & Corporate [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	37		33		119		135
Income from Equity Method Investees	0		0		0		0
Total Revenues	37		33		119		135
DD&A	19		18		57		57
Gain on Divestitures	0		0		0		0
Asset Impairments	0		0		0		0
(Gain) Loss on Commodity Derivative Instruments	0	[1]	0	[1]	0		0
Income (Loss) from Continuing Operations Before Income Taxes	(129)		(136)		(446)		(372)
Total Assets	$ 425				$ 425				$ 675

[1] 4. Derivative Instruments and Hedging Activities.