Segment Information (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) Operating_Segment	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | Operating_Segment			5
Crude Oil, NGL and Natural Gas Revenues from Third Parties	$ 1,017	$ 823	$ 2,011	$ 1,528
Income from Equity Method Investees and Other	42	24	84	43
Intersegment Revenues	0	0	0	0
Total	1,059	847	2,095	1,571
DD&A	503	622	1,031	1,239
Loss on Marcellus Shale Upstream Divestiture	2,322	0	2,322	0
(Gain) Loss on Commodity Derivative Instruments	(57)	151	(167)	107
Loss on Divestitures		23		23
Income (Loss) Before Income Taxes	(2,334)	(498)	(2,275)	(951)
Goodwill	1,289		1,289		$ 0
Total Assets	21,574		21,574		21,011
Midstream United States
Segment Reporting Information [Line Items]
Crude Oil, NGL and Natural Gas Revenues from Third Parties	0	0	0	0
Income from Equity Method Investees and Other	17	15	32	31
Intersegment Revenues	69	43	127	85
Total	86	58	159	116
DD&A	5	5	10	9
Loss on Marcellus Shale Upstream Divestiture	0		0
(Gain) Loss on Commodity Derivative Instruments	0	0	0	0
Loss on Divestitures		0		0
Income (Loss) Before Income Taxes	58	39	107	80
Goodwill	0		0
Total Assets	1,106		1,106		851
Operating Segments | United States
Segment Reporting Information [Line Items]
Crude Oil, NGL and Natural Gas Revenues from Third Parties	780	576	1,550	1,065
Income from Equity Method Investees and Other	0	0	0	0
Intersegment Revenues	0	0	0	0
Total	780	576	1,550	1,065
DD&A	427	539	886	1,064
Loss on Marcellus Shale Upstream Divestiture	2,322		2,322
(Gain) Loss on Commodity Derivative Instruments	(51)	129	(154)	92
Loss on Divestitures		23		23
Income (Loss) Before Income Taxes	(2,319)	(409)	(2,251)	(743)
Goodwill	1,289		1,289
Total Assets	16,143		16,143		16,079
Operating Segments | Eastern Mediterranean
Segment Reporting Information [Line Items]
Crude Oil, NGL and Natural Gas Revenues from Third Parties	133	131	265	257
Income from Equity Method Investees and Other	0	0	0	0
Intersegment Revenues	0	0	0	0
Total	133	131	265	257
DD&A	19	19	37	39
Loss on Marcellus Shale Upstream Divestiture	0		0
(Gain) Loss on Commodity Derivative Instruments	0	0	0	0
Loss on Divestitures		0		0
Income (Loss) Before Income Taxes	106	71	207	155
Goodwill	0		0
Total Assets	2,594		2,594		2,233
Operating Segments | West Africa
Segment Reporting Information [Line Items]
Crude Oil, NGL and Natural Gas Revenues from Third Parties	104	116	196	206
Income from Equity Method Investees and Other	25	9	52	12
Intersegment Revenues	0	0	0	0
Total	129	125	248	218
DD&A	39	49	74	104
Loss on Marcellus Shale Upstream Divestiture	0		0
(Gain) Loss on Commodity Derivative Instruments	(6)	22	(13)	15
Loss on Divestitures		0		0
Income (Loss) Before Income Taxes	72	18	138	27
Goodwill	0		0
Total Assets	1,437		1,437		1,479
Operating Segments | Other Int'l
Segment Reporting Information [Line Items]
Crude Oil, NGL and Natural Gas Revenues from Third Parties	0	0	0	0
Income from Equity Method Investees and Other	0	0	0	0
Intersegment Revenues	0	0	0	0
Total	0	0	0	0
DD&A	1	1	2	3
Loss on Marcellus Shale Upstream Divestiture	0		0
(Gain) Loss on Commodity Derivative Instruments	0	0	0	0
Loss on Divestitures		0		0
Income (Loss) Before Income Taxes	(4)	(8)	(11)	(70)
Goodwill	0		0
Total Assets	83		83		89
Intersegment Eliminations
Segment Reporting Information [Line Items]
Crude Oil, NGL and Natural Gas Revenues from Third Parties	0	0	0	0
Income from Equity Method Investees and Other	0	0	0	0
Intersegment Revenues	(69)	(43)	(127)	(85)
Total	(69)	(43)	(127)	(85)
DD&A	0	0	0	0
Loss on Marcellus Shale Upstream Divestiture	0		0
(Gain) Loss on Commodity Derivative Instruments	0	0	0	0
Loss on Divestitures		0		0
Income (Loss) Before Income Taxes	(13)	0	(35)	0
Goodwill	0		0
Total Assets	(131)		(131)		(19)
Corporate
Segment Reporting Information [Line Items]
Crude Oil, NGL and Natural Gas Revenues from Third Parties	0	0	0	0
Income from Equity Method Investees and Other	0	0	0	0
Intersegment Revenues	0		0	0
Total	0	0	0	0
DD&A	12	9	22	20
Loss on Marcellus Shale Upstream Divestiture	0		0
(Gain) Loss on Commodity Derivative Instruments	0	0	0	0
Loss on Divestitures		0		0
Income (Loss) Before Income Taxes	(234)	$ (209)	(430)	$ (400)
Goodwill	0		0
Total Assets	$ 342		$ 342		$ 299