Segment Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Segment Reporting Information [Line Items]
Revenues from Third Parties	$ 765	$ 1,228	$ 2,227	$ 3,893
Income (Loss) from Equity Method Investees	36	41	60	138
DD&A	539	460	1,444	1,297
Gain on Divestitures	0	(30)	0	(72)
Asset Impairments	0	33	43	164
Gain on Commodity Derivative Instruments	(267)	(385)	(331)	(74)
Total Revenues	801	1,269	2,287	4,031
Income (Loss) Before Income Taxes	(259)	576	(593)	1,085
Total Assets	25,965		25,965		$ 22,553
United States [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	492	819	1,411	2,503
Income (Loss) from Equity Method Investees	16	0	35	0
DD&A	437	351	1,138	970
Gain on Divestitures		(30)		(36)
Asset Impairments		33	11	56
Gain on Commodity Derivative Instruments	(187)	(252)	(231)	(6)
Total Revenues	508	819	1,446	2,503
Income (Loss) Before Income Taxes	(189)	457	(353)	838
Total Assets	20,052		20,052		16,400
West Africa [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	120	269	432	931
Income (Loss) from Equity Method Investees	20	41	25	138
DD&A	67	70	223	218
Gain on Divestitures		0		0
Asset Impairments		0	0	0
Gain on Commodity Derivative Instruments	(80)	(133)	(100)	(68)
Total Revenues	140	310	457	1,069
Income (Loss) Before Income Taxes	98	321	195	786
Total Assets	2,240		2,240		2,763
Eastern Mediterranean [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	152	138	378	363
Income (Loss) from Equity Method Investees	0	0	0	0
DD&A	22	17	52	46
Gain on Divestitures		0		0
Asset Impairments		0	32	14
Gain on Commodity Derivative Instruments	0	0	0	0
Total Revenues	152	138	378	363
Income (Loss) Before Income Taxes	107	90	227	211
Total Assets	2,503		2,503		2,806
Other Int'l & Corporate [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	1	2	6	96
Income (Loss) from Equity Method Investees	0	0	0	0
DD&A	13	22	31	63
Gain on Divestitures		0		(36)
Asset Impairments		0	0	94
Gain on Commodity Derivative Instruments	0	0	0	0
Total Revenues	1	2	6	96
Income (Loss) Before Income Taxes	(275)	$ (292)	(662)	$ (750)
Total Assets	$ 1,170		$ 1,170		$ 584