Segment Information - Operating Results by Segment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Segment Reporting Information
Revenue from sales	$ 571	$ 1,093	$ 1,591	$ 2,145
Lease Operating Expense	98	122	236	273
Production and Ad Valorem Taxes	24	41	63	90
Gathering, Transportation and Processing Expense	89	96	184	198
Asset Impairments	51	0	2,754	0
Total	214	260	490	565
Exploration Expense	15	33	1,519	57
Depreciation, Depletion and Amortization	320	528	812	1,036
Asset Impairments	51
Goodwill Impairment	0	0	110	0
Firm Transportation Exit Cost				92
(Gain) Loss on Commodity Derivative Instruments	158	(60)	(231)	152
Income (Loss) Before Income Taxes	(476)	28	(4,494)	(345)
Additions to Long-Lived Assets, Excluding Acquisitions	106	647	548	1,359
Additions to Equity Method Investments	3	144	155
Property, Plant and Equipment, Net	12,986		12,986		$ 17,451
Equity Method Investment, Nonconsolidated Investee or Group of Investees
Segment Reporting Information
Revenue from sales				415
Operating Segments | Equity Method Investment, Nonconsolidated Investee or Group of Investees
Segment Reporting Information
Revenue from sales				415
Intersegment Eliminations and Other
Segment Reporting Information
Revenue from sales	(92)	(91)	(207)	(197)
Lease Operating Expense	(17)	(12)	(31)	(21)
Production and Ad Valorem Taxes	0	0	0	0
Gathering, Transportation and Processing Expense	(67)	(59)	(142)	(128)
Asset Impairments			0
Total	(84)	(71)	(173)	(149)
Exploration Expense	0		0
Depreciation, Depletion and Amortization	(8)	(6)	(17)	(13)
Asset Impairments	0
(Gain) Loss on Commodity Derivative Instruments	0	0	0	0
Income (Loss) Before Income Taxes	11	(15)	0	(29)
Additions to Long-Lived Assets, Excluding Acquisitions	(4)	(25)	(28)	(48)
Additions to Equity Method Investments	0	0	0
Property, Plant and Equipment, Net	(222)		(222)		(223)
Corporate
Segment Reporting Information
Revenue from sales	16	23	33	50
Lease Operating Expense	0	0	0	0
Production and Ad Valorem Taxes	0	0	0	0
Gathering, Transportation and Processing Expense	0	0	0	0
Asset Impairments			0
Total	0	0	0	0
Exploration Expense	0		0
Depreciation, Depletion and Amortization	12	15	25	30
Asset Impairments	0
Firm Transportation Exit Cost				92
(Gain) Loss on Commodity Derivative Instruments	0	0	0	0
Income (Loss) Before Income Taxes	(194)	(182)	(402)	(446)
Additions to Long-Lived Assets, Excluding Acquisitions	6	9	13	18
Additions to Equity Method Investments	0	0	0
Property, Plant and Equipment, Net	164		164		216
United States | Operating Segments
Segment Reporting Information
Revenue from sales	321	802	960	1,565
Lease Operating Expense	81	114	189	239
Production and Ad Valorem Taxes	23	40	60	87
Gathering, Transportation and Processing Expense	133	124	279	266
Asset Impairments			2,703
Total	240	279	535	596
Exploration Expense	5		1,499
Depreciation, Depletion and Amortization	252	457	671	896
Asset Impairments	0
(Gain) Loss on Commodity Derivative Instruments	149	(58)	(240)	130
Income (Loss) Before Income Taxes	(359)	70	(4,276)	(177)
Additions to Long-Lived Assets, Excluding Acquisitions	65	478	422	990
Additions to Equity Method Investments	0	0	0
Property, Plant and Equipment, Net	7,473		7,473		11,859
Eastern Mediter-ranean | Operating Segments
Segment Reporting Information
Revenue from sales	138	107	327	225
Lease Operating Expense	15	9	28	19
Production and Ad Valorem Taxes	0	0	0	0
Gathering, Transportation and Processing Expense	3	0	6	0
Asset Impairments			0
Total	18	9	34	19
Exploration Expense	2		4
Depreciation, Depletion and Amortization	16	17	35	33
Asset Impairments	0
(Gain) Loss on Commodity Derivative Instruments	0	0	0	0
Income (Loss) Before Income Taxes	83	65	228	149
Additions to Long-Lived Assets, Excluding Acquisitions	13	119	44	251
Additions to Equity Method Investments	0	0	0
Property, Plant and Equipment, Net	3,058		3,058		3,041
West Africa | Operating Segments
Segment Reporting Information
Revenue from sales	44	91	116	176
Lease Operating Expense	20	10	50	34
Production and Ad Valorem Taxes	0	0	0	0
Gathering, Transportation and Processing Expense	0	0	0	0
Asset Impairments			51
Total	20	10	50	34
Exploration Expense	5		8
Depreciation, Depletion and Amortization	22	19	46	39
Asset Impairments	51
(Gain) Loss on Commodity Derivative Instruments	9	(2)	9	22
Income (Loss) Before Income Taxes	(69)	59	(59)	70
Additions to Long-Lived Assets, Excluding Acquisitions	19	12	38	18
Additions to Equity Method Investments	0	0	0
Property, Plant and Equipment, Net	737		737		793
Other Int'l | Operating Segments
Segment Reporting Information
Revenue from sales	0	0	0	0
Lease Operating Expense	0	0	0	0
Production and Ad Valorem Taxes	0	0	0	0
Gathering, Transportation and Processing Expense	0	0	0	0
Asset Impairments			0
Total	0	0	0	0
Exploration Expense	3		8
Depreciation, Depletion and Amortization	0	0	0	0
Asset Impairments	0
(Gain) Loss on Commodity Derivative Instruments	0	0	0	0
Income (Loss) Before Income Taxes	(6)	(15)	(12)	(31)
Additions to Long-Lived Assets, Excluding Acquisitions	2	2	11	12
Additions to Equity Method Investments	0	0	0
Property, Plant and Equipment, Net	55		55		44
Midstream | Operating Segments
Segment Reporting Information
Revenue from sales	144	161	362	326
Lease Operating Expense	(1)	1	0	2
Production and Ad Valorem Taxes	1	1	3	3
Gathering, Transportation and Processing Expense	20	31	41	60
Asset Impairments			0
Total	20	33	44	65
Exploration Expense	0		0
Depreciation, Depletion and Amortization	26	26	52	51
Asset Impairments	0
Goodwill Impairment			110
(Gain) Loss on Commodity Derivative Instruments	0	0	0	0
Income (Loss) Before Income Taxes	58	46	27	119
Additions to Long-Lived Assets, Excluding Acquisitions	5	52	48	118
Additions to Equity Method Investments	3	144	155
Property, Plant and Equipment, Net	1,721		1,721		$ 1,721
Midstream | Intersegment Eliminations and Other
Segment Reporting Information
Revenue from sales	92	91	207	197
Total Crude Oil, NGL and Natural Gas Sales
Segment Reporting Information
Revenue from sales	493	954	1,387	1,891
Total Crude Oil, NGL and Natural Gas Sales | Intersegment Eliminations and Other
Segment Reporting Information
Revenue from sales	0	0	0	0
Total Crude Oil, NGL and Natural Gas Sales | Corporate
Segment Reporting Information
Revenue from sales	0	0	0	0
Total Crude Oil, NGL and Natural Gas Sales | United States | Operating Segments
Segment Reporting Information
Revenue from sales	318	773	932	1,522
Total Crude Oil, NGL and Natural Gas Sales | Eastern Mediter-ranean | Operating Segments
Segment Reporting Information
Revenue from sales	139	107	330	225
Total Crude Oil, NGL and Natural Gas Sales | West Africa | Operating Segments
Segment Reporting Information
Revenue from sales	36	74	125	144
Total Crude Oil, NGL and Natural Gas Sales | Other Int'l | Operating Segments
Segment Reporting Information
Revenue from sales	0	0	0	0
Total Crude Oil, NGL and Natural Gas Sales | Midstream | Operating Segments
Segment Reporting Information
Revenue from sales	0	0	0	0
Crude Oil Sales
Segment Reporting Information
Revenue from sales	261	688	839	1,300
Crude Oil Sales | Intersegment Eliminations and Other
Segment Reporting Information
Revenue from sales	0	0	0	0
Crude Oil Sales | Corporate
Segment Reporting Information
Revenue from sales	0	0	0	0
Crude Oil Sales | United States | Operating Segments
Segment Reporting Information
Revenue from sales	230	617	722	1,162
Crude Oil Sales | Eastern Mediter-ranean | Operating Segments
Segment Reporting Information
Revenue from sales	0	2	1	3
Crude Oil Sales | West Africa | Operating Segments
Segment Reporting Information
Revenue from sales	31	69	116	135
Crude Oil Sales | Other Int'l | Operating Segments
Segment Reporting Information
Revenue from sales	0	0	0	0
Crude Oil Sales | Midstream | Operating Segments
Segment Reporting Information
Revenue from sales	0	0	0	0
NGL Sales
Segment Reporting Information
Revenue from sales	40	84	102	180
NGL Sales | Intersegment Eliminations and Other
Segment Reporting Information
Revenue from sales	0	0	0	0
NGL Sales | Corporate
Segment Reporting Information
Revenue from sales	0	0	0	0
NGL Sales | United States | Operating Segments
Segment Reporting Information
Revenue from sales	40	84	102	180
NGL Sales | Eastern Mediter-ranean | Operating Segments
Segment Reporting Information
Revenue from sales	0	0	0	0
NGL Sales | West Africa | Operating Segments
Segment Reporting Information
Revenue from sales	0	0	0	0
NGL Sales | Other Int'l | Operating Segments
Segment Reporting Information
Revenue from sales	0	0	0	0
NGL Sales | Midstream | Operating Segments
Segment Reporting Information
Revenue from sales	0	0	0	0
Natural Gas Sales
Segment Reporting Information
Revenue from sales	192	182	446	411
Natural Gas Sales | Intersegment Eliminations and Other
Segment Reporting Information
Revenue from sales	0	0	0	0
Natural Gas Sales | Corporate
Segment Reporting Information
Revenue from sales	0	0	0	0
Natural Gas Sales | United States | Operating Segments
Segment Reporting Information
Revenue from sales	48	72	108	180
Natural Gas Sales | Eastern Mediter-ranean | Operating Segments
Segment Reporting Information
Revenue from sales	139	105	329	222
Natural Gas Sales | West Africa | Operating Segments
Segment Reporting Information
Revenue from sales	5	5	9	9
Natural Gas Sales | Other Int'l | Operating Segments
Segment Reporting Information
Revenue from sales	0	0	0	0
Natural Gas Sales | Midstream | Operating Segments
Segment Reporting Information
Revenue from sales	0	0	0	0
Sales of Purchased Oil and Gas
Segment Reporting Information
Revenue from sales	49	103	174	177
Other Royalty Expense	63	113	202	200
Sales of Purchased Oil and Gas | Intersegment Eliminations and Other
Segment Reporting Information
Revenue from sales	0	0	0	0
Other Royalty Expense	0	0
Sales of Purchased Oil and Gas | Corporate
Segment Reporting Information
Revenue from sales	16	23	33	50
Other Royalty Expense	30	37
Sales of Purchased Oil and Gas | United States | Operating Segments
Segment Reporting Information
Revenue from sales	4	28	29	42
Other Royalty Expense	4	28
Sales of Purchased Oil and Gas | Eastern Mediter-ranean | Operating Segments
Segment Reporting Information
Revenue from sales	0	0	0	0
Other Royalty Expense	0	0
Sales of Purchased Oil and Gas | West Africa | Operating Segments
Segment Reporting Information
Revenue from sales	0	0	0	0
Other Royalty Expense	0	0
Sales of Purchased Oil and Gas | Other Int'l | Operating Segments
Segment Reporting Information
Revenue from sales	0	0	0	0
Other Royalty Expense	0	0
Sales of Purchased Oil and Gas | Midstream | Operating Segments
Segment Reporting Information
Revenue from sales	29	52	112	85
Other Royalty Expense	29	48
(Loss) Income from Equity Method Investments and Other
Segment Reporting Information
Revenue from sales	3	16	(21)	33
(Loss) Income from Equity Method Investments and Other | Intersegment Eliminations and Other
Segment Reporting Information
Revenue from sales	0	0	0	0
(Loss) Income from Equity Method Investments and Other | Corporate
Segment Reporting Information
Revenue from sales	0	0	0	0
(Loss) Income from Equity Method Investments and Other | United States | Operating Segments
Segment Reporting Information
Revenue from sales	(1)	1	(1)	1
(Loss) Income from Equity Method Investments and Other | Eastern Mediter-ranean | Operating Segments
Segment Reporting Information
Revenue from sales	(1)	0	(3)	0
(Loss) Income from Equity Method Investments and Other | West Africa | Operating Segments
Segment Reporting Information
Revenue from sales	8	17	(9)	32
(Loss) Income from Equity Method Investments and Other | Other Int'l | Operating Segments
Segment Reporting Information
Revenue from sales	0	0	0	0
(Loss) Income from Equity Method Investments and Other | Midstream | Operating Segments
Segment Reporting Information
Revenue from sales	(3)	(2)	(8)	0
Midstream Services Revenues – Third Party
Segment Reporting Information
Revenue from sales	26	20	51	44
Midstream Services Revenues – Third Party | Intersegment Eliminations and Other
Segment Reporting Information
Revenue from sales	0	0	0	0
Midstream Services Revenues – Third Party | Corporate
Segment Reporting Information
Revenue from sales	0	0	0	0
Midstream Services Revenues – Third Party | United States | Operating Segments
Segment Reporting Information
Revenue from sales	0	0	0	0
Midstream Services Revenues – Third Party | Eastern Mediter-ranean | Operating Segments
Segment Reporting Information
Revenue from sales	0	0	0	0
Midstream Services Revenues – Third Party | West Africa | Operating Segments
Segment Reporting Information
Revenue from sales	0	0	0	0
Midstream Services Revenues – Third Party | Other Int'l | Operating Segments
Segment Reporting Information
Revenue from sales	0	0	0	0
Midstream Services Revenues – Third Party | Midstream | Operating Segments
Segment Reporting Information
Revenue from sales	26	20	51	44
Other Royalty Expense
Segment Reporting Information
Other Royalty Expense	3	1	7	4
Other Royalty Expense | Intersegment Eliminations and Other
Segment Reporting Information
Other Royalty Expense	0	0	0	0
Other Royalty Expense | Corporate
Segment Reporting Information
Other Royalty Expense	0	0	0	0
Other Royalty Expense | United States | Operating Segments
Segment Reporting Information
Other Royalty Expense	3	1	7	4
Other Royalty Expense | Eastern Mediter-ranean | Operating Segments
Segment Reporting Information
Other Royalty Expense	0	0	0	0
Other Royalty Expense | West Africa | Operating Segments
Segment Reporting Information
Other Royalty Expense	0	0	0	0
Other Royalty Expense | Other Int'l | Operating Segments
Segment Reporting Information
Other Royalty Expense	0	0	0	0
Other Royalty Expense | Midstream | Operating Segments
Segment Reporting Information
Other Royalty Expense	$ 0	$ 0	0	0
Cost of Purchased Oil and Gas
Segment Reporting Information
Other Royalty Expense			202	200
Cost of Purchased Oil and Gas | Intersegment Eliminations and Other
Segment Reporting Information
Other Royalty Expense			0	0
Cost of Purchased Oil and Gas | Corporate
Segment Reporting Information
Other Royalty Expense			61	79
Cost of Purchased Oil and Gas | United States | Operating Segments
Segment Reporting Information
Other Royalty Expense			32	42
Cost of Purchased Oil and Gas | Eastern Mediter-ranean | Operating Segments
Segment Reporting Information
Other Royalty Expense			0	0
Cost of Purchased Oil and Gas | West Africa | Operating Segments
Segment Reporting Information
Other Royalty Expense			0	0
Cost of Purchased Oil and Gas | Other Int'l | Operating Segments
Segment Reporting Information
Other Royalty Expense			0	0
Cost of Purchased Oil and Gas | Midstream | Operating Segments
Segment Reporting Information
Other Royalty Expense			$ 109	$ 79