Segment Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
Revenues from Third Parties	$ 994	$ 705
Income from Equity Method Investees	42	19
Total Revenues	1,036	724
DD&A	528	617
Gain on Commodity Derivative Instruments	(110)	(44)
Income (Loss) Before Income Taxes	59	(453)
Total Assets	21,008		$ 21,011
United States [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	770	489
Income from Equity Method Investees	14	16
Total Revenues	784	505
DD&A	463	530
Gain on Commodity Derivative Instruments	(102)	(37)
Income (Loss) Before Income Taxes	96	(292)
Total Assets	16,997		17,029
West Africa [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	93	90
Income from Equity Method Investees	28	3
Total Revenues	121	93
DD&A	34	55
Gain on Commodity Derivative Instruments	(8)	(7)
Income (Loss) Before Income Taxes	66	9
Total Assets	1,401		1,479
Eastern Mediterranean [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	131	126
Income from Equity Method Investees	0	0
Total Revenues	131	126
DD&A	19	20
Gain on Commodity Derivative Instruments	0	0
Income (Loss) Before Income Taxes	101	84
Total Assets	2,391		2,233
Other Int'l & Corporate [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	0	0
Income from Equity Method Investees	0	0
Total Revenues	0	0
DD&A	12	12
Gain on Commodity Derivative Instruments	0	0
Income (Loss) Before Income Taxes	(204)	$ (254)
Total Assets	$ 219		$ 270