Segment Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Segment Reporting Information [Line Items]
Revenues from Third Parties	$ 823	$ 732	$ 1,528	$ 1,481
Income from Equity Method Investees	24	6	43	24
Total Revenues	847	738	1,571	1,505
DD&A	622	451	1,239	905
Loss on Divestitures	23	(1)	23	0
Asset Impairments	0	15	0	43
Loss (Gain) on Commodity Derivative Instruments	151	87	107	(63)
(Loss) Income Before Income Taxes	(498)	(293)	(951)	(334)
Total Assets	22,516		22,516		$ 24,196
United States [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	576	451	1,065	938
Income from Equity Method Investees	15	8	31	19
Total Revenues	591	459	1,096	957
DD&A	544	344	1,074	701
Loss on Divestitures	23	(1)	23	0
Asset Impairments		8		11
Loss (Gain) on Commodity Derivative Instruments	129	62	92	(43)
(Loss) Income Before Income Taxes	(183)	(163)	(475)	(164)
Total Assets	17,742		17,742		18,831
West Africa [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	116	174	206	312
Income from Equity Method Investees	9	(2)	12	5
Total Revenues	125	172	218	317
DD&A	49	79	104	156
Loss on Divestitures	0	0	0	0
Asset Impairments		0		0
Loss (Gain) on Commodity Derivative Instruments	22	25	15	(20)
(Loss) Income Before Income Taxes	18	23	27	97
Total Assets	2,087		2,087		2,299
Eastern Mediterranean [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	131	106	257	226
Income from Equity Method Investees	0	0	0	0
Total Revenues	131	106	257	226
DD&A	19	15	39	30
Loss on Divestitures	0	0	0	0
Asset Impairments		7		32
Loss (Gain) on Commodity Derivative Instruments	0	0	0	0
(Loss) Income Before Income Taxes	71	69	155	120
Total Assets	2,424		2,424		2,677
Other Int'l & Corporate [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	0	1	0	5
Income from Equity Method Investees	0	0	0	0
Total Revenues	0	1	0	5
DD&A	10	13	22	18
Loss on Divestitures	0	0	0	0
Asset Impairments		0		0
Loss (Gain) on Commodity Derivative Instruments	0	0	0	0
(Loss) Income Before Income Taxes	(404)	$ (222)	(658)	$ (387)
Total Assets	$ 263		$ 263		$ 389