Segment Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Segment Reporting Information [Line Items]
Revenues from Third Parties	$ 882	$ 783	$ 2,411	$ 2,264
Income from Equity Method Investees	28	36	70	60
Total Revenues	910	819	2,481	2,324
DD&A	621	539	1,859	1,444
Loss on Divestitures	0	0	23	0
Asset Impairments	0	0	0	43
(Gain) Loss on Commodity Derivative Instruments	(55)	(267)	53	(331)
(Loss) Income Before Income Taxes	(280)	(259)	(1,231)	(593)
Total Assets	22,469		22,469		$ 24,196
United States [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	639	510	1,705	1,448
Income from Equity Method Investees	8	16	39	35
Total Revenues	647	526	1,744	1,483
DD&A	539	437	1,612	1,138
Loss on Divestitures			23
(Gain) Loss on Commodity Derivative Instruments	(48)	(187)	44	(231)
(Loss) Income Before Income Taxes	(407)	(189)	(882)	(353)
Total Assets	17,752		17,752		18,831
West Africa [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	93	120	299	432
Income from Equity Method Investees	20	20	31	25
Total Revenues	113	140	330	457
DD&A	46	67	150	223
Loss on Divestitures			0
(Gain) Loss on Commodity Derivative Instruments	(7)	(80)	9	(100)
(Loss) Income Before Income Taxes	47	98	74	195
Total Assets	1,975		1,975		2,299
Eastern Mediterranean [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	150	152	407	378
Income from Equity Method Investees	0	0	0	0
Total Revenues	150	152	407	378
DD&A	23	22	62	52
Loss on Divestitures			0
(Gain) Loss on Commodity Derivative Instruments	0	0	0	0
(Loss) Income Before Income Taxes	135	107	290	227
Total Assets	2,515		2,515		2,677
Other Int'l & Corporate [Member]
Segment Reporting Information [Line Items]
Revenues from Third Parties	0	1	0	6
Income from Equity Method Investees	0	0	0	0
Total Revenues	0	1	0	6
DD&A	13	13	35	31
Loss on Divestitures			0
(Gain) Loss on Commodity Derivative Instruments	0	0	0	0
(Loss) Income Before Income Taxes	(55)	$ (275)	(713)	$ (662)
Total Assets	$ 227		$ 227		$ 389