Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012		Dec. 31, 2012
Segment Reporting Information [Line Items]
Revenues from Third Parties	$ 1,083		$ 1,037
Income from Equity Method Investees	60		51
Total	1,143		1,088
DD&A	366		294
(Gain) Loss on Commodity Derivative Instruments	72	[1]	96	[1]
Income from Continuing Operations Before Income Taxes	318		335
Total Assets	17,667				17,509
United States [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	716		554
Income from Equity Method Investees	0		0
Total	716		554
DD&A	266		198
(Gain) Loss on Commodity Derivative Instruments	49	[1]	(9)	[1]
Income from Continuing Operations Before Income Taxes	243		193
Total Assets	11,398				11,199
West Africa [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	273		383
Income from Equity Method Investees	60		51
Total	333		434
DD&A	54		73
(Gain) Loss on Commodity Derivative Instruments	23	[1]	105	[1]
Income from Continuing Operations Before Income Taxes	231		227
Total Assets	3,183				3,063
Eastern Mediterranean [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	51		44
Income from Equity Method Investees	0		0
Total	51		44
DD&A	28		5
(Gain) Loss on Commodity Derivative Instruments	0		0
Income from Continuing Operations Before Income Taxes	15		32
Total Assets	2,631				2,572
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	43		56
Income from Equity Method Investees	0		0
Total	43		56
DD&A	18		18
(Gain) Loss on Commodity Derivative Instruments	0		0
Income from Continuing Operations Before Income Taxes	(171)		(117)
Total Assets	$ 455				$ 675

[1] See Note 4. Derivative Instruments and Hedging Activities.