Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012		Dec. 31, 2012
Segment Reporting Information [Line Items]
Revenues from Third Parties	$ 1,112		$ 934		$ 2,196		$ 1,970
Income from Equity Method Investees	37		31		96		83
Total Revenues	1,149		965		2,292		2,053
DD&A	368		325		734		619
Gain on Commodity Derivative Instruments	(161)	[1]	(276)	[1]	(89)	[1]	(180)	[1]
Income from Continuing Operations Before Income Taxes	486		390		804		724
Total Assets	17,961				17,961				17,509
United States [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	683		527		1,399		1,080
Income from Equity Method Investees	0		0		0		0
Total Revenues	683		527		1,399		1,080
DD&A	258		232		524		430
Gain on Commodity Derivative Instruments	(111)	[1]	(93)	[1]	(62)	[1]	(102)	[1]
Income from Continuing Operations Before Income Taxes	320		48		563		241
Total Assets	11,899				11,899				11,199
West Africa [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	290		332		563		715
Income from Equity Method Investees	37		31		96		83
Total Revenues	327		363		659		798
DD&A	63		62		117		135
Gain on Commodity Derivative Instruments	(50)	[1]	(183)	[1]	(27)	[1]	(78)	[1]
Income from Continuing Operations Before Income Taxes	268		455		499		682
Total Assets	3,022				3,022				3,063
Eastern Mediterranean [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	101		29		152		73
Income from Equity Method Investees	0		0		0		0
Total Revenues	101		29		152		73
DD&A	27		10		55		15
Gain on Commodity Derivative Instruments	0	[1]	0	[1]	0		0
Income from Continuing Operations Before Income Taxes	44		5		59		37
Total Assets	2,679				2,679				2,572
Other Int'l & Corporate
Segment Reporting Information [Line Items]
Revenues from Third Parties	38		46		82		102
Income from Equity Method Investees	0		0		0		0
Total Revenues	38		46		82		102
DD&A	20		21		38		39
Gain on Commodity Derivative Instruments	0	[1]	0	[1]	0		0
Income from Continuing Operations Before Income Taxes	(146)		(118)		(317)		(236)
Total Assets	$ 361				$ 361				$ 675

[1] 4. Derivative Instruments and Hedging Activities.