Segment Information - Operating Results by Segment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Revenue from Sales	$ 1,093	$ 1,230	$ 2,145	$ 2,516
Revenues	1,093	1,230	2,145	2,516
Lease Operating Expense	122	132	273	287
Production and Ad Valorem Taxes	41	50	90	104
Gathering, Transportation and Processing Expense	96	98	198	191
Total Production Expense	260	290	565	609
Marcellus Shale Exit Cost			92
Depreciation, Depletion and Amortization	528	465	1,036	933
(Gain) Loss on Divestitures, Net	0	(78)	0	(666)
Asset Impairments				168
(Gain) Loss on Commodity Derivative Instruments	(60)	249	152	328
Income (Loss) Before Income Taxes	28	10	(345)	553
Additions to Long-Lived Assets, Excluding Acquisitions	647	935	1,359	1,840
Investments in Equity Method Investees	144		415	0
Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue from Sales	(91)	(85)	(197)	(166)
Lease Operating Expense	(12)	(6)	(21)	(6)
Production and Ad Valorem Taxes	0	0	0	0
Gathering, Transportation and Processing Expense	(59)	(55)	(128)	(108)
Total Production Expense	(71)	(61)	(149)	(114)
Marcellus Shale Exit Cost			0
Depreciation, Depletion and Amortization	(6)	(4)	(13)	(8)
(Gain) Loss on Divestitures, Net		0		0
Asset Impairments				0
(Gain) Loss on Commodity Derivative Instruments	0	0	0	0
Income (Loss) Before Income Taxes	(15)	(18)	(29)	(40)
Additions to Long-Lived Assets, Excluding Acquisitions	(25)	(18)	(48)	(50)
Investments in Equity Method Investees	0		0
Corporate
Segment Reporting Information [Line Items]
Revenue from Sales	23	24	50	55
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
Total Production Expense	0	0	0	0
Marcellus Shale Exit Cost			92
Depreciation, Depletion and Amortization	15	12	30	23
(Gain) Loss on Divestitures, Net		0		0
Asset Impairments				0
(Gain) Loss on Commodity Derivative Instruments	0	0	0	0
Income (Loss) Before Income Taxes	(182)	(154)	(446)	(328)
Additions to Long-Lived Assets, Excluding Acquisitions	9	18	18	28
Investments in Equity Method Investees	0		0
United States | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	802	870	1,565	1,818
Lease Operating Expense	114	114	239	240
Production and Ad Valorem Taxes	40	48	87	101
Gathering, Transportation and Processing Expense	124	131	266	256
Total Production Expense	279	303	596	624
Marcellus Shale Exit Cost			0
Depreciation, Depletion and Amortization	457	394	896	800
(Gain) Loss on Divestitures, Net		21		15
Asset Impairments				168
(Gain) Loss on Commodity Derivative Instruments	(58)	196	130	260
Income (Loss) Before Income Taxes	70	(90)	(177)	(127)
Additions to Long-Lived Assets, Excluding Acquisitions	478	561	990	1,095
Investments in Equity Method Investees	0		0
United States | Noble Midstream
Segment Reporting Information [Line Items]
Revenue from Sales	161	155	326	283
Lease Operating Expense	1	0	2	0
Production and Ad Valorem Taxes	1	2	3	3
Gathering, Transportation and Processing Expense	31	22	60	43
Total Production Expense	33	24	65	46
Marcellus Shale Exit Cost			0
Depreciation, Depletion and Amortization	26	22	51	38
(Gain) Loss on Divestitures, Net		(109)		(305)
Asset Impairments				0
(Gain) Loss on Commodity Derivative Instruments	0	0	0	0
Income (Loss) Before Income Taxes	46	175	119	428
Additions to Long-Lived Assets, Excluding Acquisitions	52	155	118	397
Investments in Equity Method Investees	144		415
United States | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue from Sales	91	85	197	166
Eastern Mediterranean | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	107	113	225	244
Lease Operating Expense	9	5	19	12
Production and Ad Valorem Taxes	0	0	0	0
Gathering, Transportation and Processing Expense	0	0	0	0
Total Production Expense	9	5	19	12
Marcellus Shale Exit Cost			0
Depreciation, Depletion and Amortization	17	15	33	28
(Gain) Loss on Divestitures, Net		10		(376)
Asset Impairments				0
(Gain) Loss on Commodity Derivative Instruments	0	0	0	0
Income (Loss) Before Income Taxes	65	62	149	535
Additions to Long-Lived Assets, Excluding Acquisitions	119	216	251	363
Investments in Equity Method Investees	0		0
West Africa | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	91	153	176	282
Lease Operating Expense	10	19	34	41
Production and Ad Valorem Taxes	0	0	0	0
Gathering, Transportation and Processing Expense	0	0	0	0
Total Production Expense	10	19	34	41
Marcellus Shale Exit Cost			0
Depreciation, Depletion and Amortization	19	26	39	52
(Gain) Loss on Divestitures, Net		0		0
Asset Impairments				0
(Gain) Loss on Commodity Derivative Instruments	(2)	53	22	68
Income (Loss) Before Income Taxes	59	48	70	112
Additions to Long-Lived Assets, Excluding Acquisitions	12	3	18	5
Investments in Equity Method Investees	0		0
Other Int'l | Operating Segments
Segment Reporting Information [Line Items]
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
Total Production Expense	0	0	0	0
Marcellus Shale Exit Cost			0
Depreciation, Depletion and Amortization	0	0	0	0
(Gain) Loss on Divestitures, Net		0		0
Asset Impairments				0
(Gain) Loss on Commodity Derivative Instruments	0	0	0	0
Income (Loss) Before Income Taxes	(15)	(13)	(31)	(27)
Additions to Long-Lived Assets, Excluding Acquisitions	2	0	12	2
Investments in Equity Method Investees	0		0
Oil, NGL and Gas Sales
Segment Reporting Information [Line Items]
Revenue from Sales	954	1,100	1,891	2,273
Oil, NGL and Gas Sales | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
Oil, NGL and Gas Sales | Corporate
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
Oil, NGL and Gas Sales | United States | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	773	870	1,522	1,818
Oil, NGL and Gas Sales | United States | Noble Midstream
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
Oil, NGL and Gas Sales | Eastern Mediterranean | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	107	113	225	244
Oil, NGL and Gas Sales | West Africa | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	74	117	144	211
Oil, NGL and Gas Sales | Other Int'l | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
Crude Oil Sales
Segment Reporting Information [Line Items]
Revenue from Sales	688	749	1,300	1,522
Crude Oil Sales | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
Crude Oil Sales | Corporate
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
Crude Oil Sales | United States | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	617	635	1,162	1,317
Crude Oil Sales | United States | Noble Midstream
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
Crude Oil Sales | Eastern Mediterranean | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	2	2	3	4
Crude Oil Sales | West Africa | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	69	112	135	201
Crude Oil Sales | Other Int'l | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
NGL Sales
Segment Reporting Information [Line Items]
Revenue from Sales	84	137	180	283
NGL Sales | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
NGL Sales | Corporate
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
NGL Sales | United States | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	84	137	180	283
NGL Sales | United States | Noble Midstream
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
NGL Sales | Eastern Mediterranean | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
NGL Sales | West Africa | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
NGL Sales | Other Int'l | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
Natural Gas Sales
Segment Reporting Information [Line Items]
Revenue from Sales	182	214	411	468
Natural Gas Sales | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
Natural Gas Sales | Corporate
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
Natural Gas Sales | United States | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	72	98	180	218
Natural Gas Sales | United States | Noble Midstream
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
Natural Gas Sales | Eastern Mediterranean | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	105	111	222	240
Natural Gas Sales | West Africa | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	5	5	9	10
Natural Gas Sales | Other Int'l | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
Cost of Purchased of Gas
Segment Reporting Information [Line Items]
Revenue from Sales	103	66	177	119
Cost of Purchased Oil and Gas	113	71	200	128
Cost of Purchased of Gas | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
Cost of Purchased Oil and Gas	0	0
Cost of Purchased of Gas | Corporate
Segment Reporting Information [Line Items]
Revenue from Sales	23	24	50	55
Cost of Purchased Oil and Gas	37	31	49	53
Cost of Purchased of Gas | United States | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	28	0	42	0
Cost of Purchased Oil and Gas	28	0
Cost of Purchased of Gas | United States | Noble Midstream
Segment Reporting Information [Line Items]
Revenue from Sales	52	42	85	64
Cost of Purchased Oil and Gas	48	40
Cost of Purchased of Gas | Eastern Mediterranean | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
Cost of Purchased Oil and Gas	0	0
Cost of Purchased of Gas | West Africa | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
Cost of Purchased Oil and Gas	0	0
Cost of Purchased of Gas | Other Int'l | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
Cost of Purchased Oil and Gas	0	0
Income (Loss) from Equity Method Investees and Other
Segment Reporting Information [Line Items]
Revenue from Sales	16	49	33	96
Income (Loss) from Equity Method Investees and Other | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
Income (Loss) from Equity Method Investees and Other | Corporate
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
Income (Loss) from Equity Method Investees and Other | United States | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	1	0	1	0
Income (Loss) from Equity Method Investees and Other | United States | Noble Midstream
Segment Reporting Information [Line Items]
Revenue from Sales	(2)	13	0	25
Income (Loss) from Equity Method Investees and Other | Eastern Mediterranean | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
Income (Loss) from Equity Method Investees and Other | West Africa | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	17	36	32	71
Income (Loss) from Equity Method Investees and Other | Other Int'l | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
Midstream Services Revenues – Third Party
Segment Reporting Information [Line Items]
Revenue from Sales	20	15	44	28
Midstream Services Revenues – Third Party | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
Midstream Services Revenues – Third Party | Corporate
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
Midstream Services Revenues – Third Party | United States | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
Midstream Services Revenues – Third Party | United States | Noble Midstream
Segment Reporting Information [Line Items]
Revenue from Sales	20	15	44	28
Midstream Services Revenues – Third Party | United States | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue from Sales	0		0
Midstream Services Revenues – Third Party | Eastern Mediterranean | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
Midstream Services Revenues – Third Party | West Africa | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
Midstream Services Revenues – Third Party | Other Int'l | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Sales	0	0	0	0
Other Royalty Expense
Segment Reporting Information [Line Items]
Cost of Purchased Oil and Gas	1	10	4	27
Other Royalty Expense | Intersegment Eliminations
Segment Reporting Information [Line Items]
Cost of Purchased Oil and Gas	0	0	0	0
Other Royalty Expense | Corporate
Segment Reporting Information [Line Items]
Cost of Purchased Oil and Gas	0	0	0	0
Other Royalty Expense | United States | Operating Segments
Segment Reporting Information [Line Items]
Cost of Purchased Oil and Gas	1	10	4	27
Other Royalty Expense | United States | Noble Midstream
Segment Reporting Information [Line Items]
Cost of Purchased Oil and Gas	0	0	0	0
Other Royalty Expense | Eastern Mediterranean | Operating Segments
Segment Reporting Information [Line Items]
Cost of Purchased Oil and Gas	0	0	0	0
Other Royalty Expense | West Africa | Operating Segments
Segment Reporting Information [Line Items]
Cost of Purchased Oil and Gas	0	0	0	0
Other Royalty Expense | Other Int'l | Operating Segments
Segment Reporting Information [Line Items]
Cost of Purchased Oil and Gas	0	0	0	0
Cost of Purchased Oil and Gas
Segment Reporting Information [Line Items]
Cost of Purchased Oil and Gas			200	128
Cost of Purchased Oil and Gas | Intersegment Eliminations
Segment Reporting Information [Line Items]
Cost of Purchased Oil and Gas			0	0
Cost of Purchased Oil and Gas | Corporate
Segment Reporting Information [Line Items]
Cost of Purchased Oil and Gas	$ 22	$ 23	79	67
Cost of Purchased Oil and Gas | United States | Operating Segments
Segment Reporting Information [Line Items]
Cost of Purchased Oil and Gas			42	0
Cost of Purchased Oil and Gas | United States | Noble Midstream
Segment Reporting Information [Line Items]
Cost of Purchased Oil and Gas			79	61
Cost of Purchased Oil and Gas | Eastern Mediterranean | Operating Segments
Segment Reporting Information [Line Items]
Cost of Purchased Oil and Gas			0	0
Cost of Purchased Oil and Gas | West Africa | Operating Segments
Segment Reporting Information [Line Items]
Cost of Purchased Oil and Gas			0	0
Cost of Purchased Oil and Gas | Other Int'l | Operating Segments
Segment Reporting Information [Line Items]
Cost of Purchased Oil and Gas			$ 0	$ 0