BUSINESS SEGMENT INFORMATION (Details)		3 Months Ended
		Mar. 31, 2021 USD ($) Segment	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)
Segment Reporting [Abstract]
Number of operating segments | Segment		3
Segment Reporting Information [Line Items]
Oil and gas production revenues		$ 0
Lease operating expenses		264,000,000	$ 335,000,000
Taxes other than income		44,000,000	33,000,000
Exploration		46,000,000	57,000,000
Depreciation, depletion, and amortization		342,000,000	566,000,000
Asset retirement obligation accretion		28,000,000	27,000,000
Impairments		0	4,472,000,000
Total operating expenses		1,276,000,000	5,647,000,000
Operating income (loss)		595,000,000	(4,303,000,000)
Other Income (Expense):
Derivative instrument gains (losses), net		158,000,000	(103,000,000)
Gain (loss) on divestitures, net		2,000,000	25,000,000
Other		61,000,000	13,000,000
General and administrative		(83,000,000)	(68,000,000)
Transaction, reorganization, and separation		0	(27,000,000)
Financing costs, net	[1]	(107,000,000)	(103,000,000)
NET INCOME (LOSS) BEFORE INCOME TAXES		626,000,000	(4,566,000,000)
Total assets		13,975,000,000	13,391,000,000	$ 12,746,000,000
Operating Segments | Egypt
Segment Reporting Information [Line Items]
Lease operating expenses		104,000,000	112,000,000
Taxes other than income		0	0
Exploration		8,000,000	18,000,000
Depreciation, depletion, and amortization		130,000,000	161,000,000
Asset retirement obligation accretion		0	0
Impairments		0	509,000,000
Total operating expenses		243,000,000	810,000,000
Operating income (loss)		231,000,000	(409,000,000)
Other Income (Expense):
Total assets		3,020,000,000	3,151,000,000
Impairments of oil and gas properties		2,000,000	511,000,000
Operating Segments | North Sea
Segment Reporting Information [Line Items]
Lease operating expenses		75,000,000	81,000,000
Taxes other than income		0	0
Exploration		20,000,000	2,000,000
Depreciation, depletion, and amortization		84,000,000	109,000,000
Asset retirement obligation accretion		19,000,000	18,000,000
Impairments		0	7,000,000
Total operating expenses		210,000,000	233,000,000
Operating income (loss)		68,000,000	64,000,000
Other Income (Expense):
Total assets		2,167,000,000	2,366,000,000
Impairments of oil and gas properties			7,000,000
Operating Segments | U.S.
Segment Reporting Information [Line Items]
Lease operating expenses		86,000,000	143,000,000
Taxes other than income		40,000,000	30,000,000
Exploration		16,000,000	35,000,000
Depreciation, depletion, and amortization		125,000,000	293,000,000
Asset retirement obligation accretion		8,000,000	8,000,000
Impairments		0	3,956,000,000
Total operating expenses		836,000,000	4,625,000,000
Operating income (loss)		280,000,000	(3,979,000,000)
Other Income (Expense):
Total assets		6,959,000,000	6,225,000,000
Impairments of oil and gas properties		16,000,000	4,000,000,000.0
Reportable Legal Entities | Altus Midstream
Segment Reporting Information [Line Items]
Oil and gas production revenues		32,000,000	41,000,000
Lease operating expenses		0	0
Taxes other than income		4,000,000	3,000,000
Exploration		0	0
Depreciation, depletion, and amortization		3,000,000	3,000,000
Asset retirement obligation accretion		1,000,000	1,000,000
Impairments		0	0
Total operating expenses		17,000,000	18,000,000
Operating income (loss)		18,000,000	23,000,000
Other Income (Expense):
Total assets		1,828,000,000	1,574,000,000
Intersegment Eliminations & Other
Segment Reporting Information [Line Items]
Oil and gas production revenues		(32,000,000)	(41,000,000)
Lease operating expenses		(1,000,000)	(1,000,000)
Taxes other than income		0	0
Exploration		2,000,000	2,000,000
Depreciation, depletion, and amortization		0	0
Asset retirement obligation accretion		0	0
Impairments		0	0
Total operating expenses		(30,000,000)	(39,000,000)
Operating income (loss)		(2,000,000)	(2,000,000)
Other Income (Expense):
Total assets		1,000,000	75,000,000
Oil and gas
Segment Reporting Information [Line Items]
Oil and gas production revenues		1,871,000,000	1,344,000,000
Oil and gas | Operating Segments | Egypt
Segment Reporting Information [Line Items]
Oil and gas production revenues		474,000,000	401,000,000
Oil and gas | Operating Segments | North Sea
Segment Reporting Information [Line Items]
Oil and gas production revenues		278,000,000	297,000,000
Oil and gas | Operating Segments | U.S.
Segment Reporting Information [Line Items]
Oil and gas production revenues		1,116,000,000	646,000,000
Oil and gas | Reportable Legal Entities | Altus Midstream
Segment Reporting Information [Line Items]
Oil and gas production revenues		35,000,000	41,000,000
Oil and gas | Intersegment Eliminations & Other
Segment Reporting Information [Line Items]
Oil and gas production revenues		(32,000,000)	(41,000,000)
Oil and gas, excluding purchased
Segment Reporting Information [Line Items]
Oil and gas production revenues		1,431,000,000	1,236,000,000
Cost of oil and gas purchased		58,000,000	71,000,000
Oil and gas, excluding purchased | Operating Segments | Egypt
Segment Reporting Information [Line Items]
Oil and gas production revenues		474,000,000	401,000,000
Cost of oil and gas purchased		1,000,000	10,000,000
Oil and gas, excluding purchased | Operating Segments | North Sea
Segment Reporting Information [Line Items]
Oil and gas production revenues		278,000,000	297,000,000
Cost of oil and gas purchased		12,000,000	16,000,000
Oil and gas, excluding purchased | Operating Segments | U.S.
Segment Reporting Information [Line Items]
Oil and gas production revenues		679,000,000	538,000,000
Cost of oil and gas purchased		69,000,000	74,000,000
Oil and gas, excluding purchased | Reportable Legal Entities | Altus Midstream
Segment Reporting Information [Line Items]
Oil and gas production revenues		0	0
Cost of oil and gas purchased		7,000,000	11,000,000
Oil and gas, excluding purchased | Intersegment Eliminations & Other
Segment Reporting Information [Line Items]
Cost of oil and gas purchased		(31,000,000)	(40,000,000)
Oil and gas, purchased
Segment Reporting Information [Line Items]
Oil and gas production revenues		440,000,000	108,000,000
Cost of oil and gas purchased		494,000,000	86,000,000
Oil and gas, purchased | Operating Segments | Egypt
Segment Reporting Information [Line Items]
Oil and gas production revenues		0	0
Cost of oil and gas purchased		0	0
Oil and gas, purchased | Operating Segments | North Sea
Segment Reporting Information [Line Items]
Oil and gas production revenues		0	0
Cost of oil and gas purchased		0	0
Oil and gas, purchased | Operating Segments | U.S.
Segment Reporting Information [Line Items]
Oil and gas production revenues		437,000,000	108,000,000
Cost of oil and gas purchased		492,000,000	86,000,000
Oil and gas, purchased | Reportable Legal Entities | Altus Midstream
Segment Reporting Information [Line Items]
Oil and gas production revenues		3,000,000	0
Cost of oil and gas purchased		2,000,000	0
Oil and gas, purchased | Intersegment Eliminations & Other
Segment Reporting Information [Line Items]
Oil and gas production revenues		0	0
Cost of oil and gas purchased		0	0
Oil | Oil and gas, excluding purchased
Segment Reporting Information [Line Items]
Oil and gas production revenues		991,000,000	1,032,000,000
Oil | Oil and gas, excluding purchased | Operating Segments | Egypt
Segment Reporting Information [Line Items]
Oil and gas production revenues		402,000,000	333,000,000
Oil | Oil and gas, excluding purchased | Operating Segments | North Sea
Segment Reporting Information [Line Items]
Oil and gas production revenues		241,000,000	271,000,000
Oil | Oil and gas, excluding purchased | Operating Segments | U.S.
Segment Reporting Information [Line Items]
Oil and gas production revenues		348,000,000	428,000,000
Oil | Oil and gas, excluding purchased | Reportable Legal Entities | Altus Midstream
Segment Reporting Information [Line Items]
Oil and gas production revenues		0	0
Oil | Oil and gas, excluding purchased | Intersegment Eliminations & Other
Segment Reporting Information [Line Items]
Oil and gas production revenues		0
Natural Gas | Oil and gas, excluding purchased
Segment Reporting Information [Line Items]
Oil and gas production revenues		312,000,000	123,000,000
Natural Gas | Oil and gas, excluding purchased | Operating Segments | Egypt
Segment Reporting Information [Line Items]
Oil and gas production revenues		70,000,000	65,000,000
Natural Gas | Oil and gas, excluding purchased | Operating Segments | North Sea
Segment Reporting Information [Line Items]
Oil and gas production revenues		31,000,000	19,000,000
Natural Gas | Oil and gas, excluding purchased | Operating Segments | U.S.
Segment Reporting Information [Line Items]
Oil and gas production revenues		211,000,000	39,000,000
Natural Gas | Oil and gas, excluding purchased | Reportable Legal Entities | Altus Midstream
Segment Reporting Information [Line Items]
Oil and gas production revenues		0	0
Natural Gas | Oil and gas, excluding purchased | Intersegment Eliminations & Other
Segment Reporting Information [Line Items]
Oil and gas production revenues		0
Natural Gas liquids | Oil and gas, excluding purchased
Segment Reporting Information [Line Items]
Oil and gas production revenues		128,000,000	81,000,000
Natural Gas liquids | Oil and gas, excluding purchased | Operating Segments | Egypt
Segment Reporting Information [Line Items]
Oil and gas production revenues		2,000,000	3,000,000
Natural Gas liquids | Oil and gas, excluding purchased | Operating Segments | North Sea
Segment Reporting Information [Line Items]
Oil and gas production revenues		6,000,000	7,000,000
Natural Gas liquids | Oil and gas, excluding purchased | Operating Segments | U.S.
Segment Reporting Information [Line Items]
Oil and gas production revenues		120,000,000	71,000,000
Natural Gas liquids | Oil and gas, excluding purchased | Reportable Legal Entities | Altus Midstream
Segment Reporting Information [Line Items]
Oil and gas production revenues		0	$ 0
Natural Gas liquids | Oil and gas, excluding purchased | Intersegment Eliminations & Other
Segment Reporting Information [Line Items]
Oil and gas production revenues		$ 0

[1] Includes amounts of $5 million associated with APA Corporation for the first quarter of 2021. Refer to Note 2—Transactions with Parent Affiliate.