SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Non-Cash Impairments of Proved and Unproved Property and Equipment (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Oil and gas proved property
Schedule Of Significant Accounting Policies [Line Items]
Asset impairments for property and equipment		$ 4,319	$ 1,484	$ 328
Oil And Gas Properties, Unproved
Schedule Of Significant Accounting Policies [Line Items]
Asset impairments for property and equipment		101	768	224
U.S. | Oil and gas proved property
Schedule Of Significant Accounting Policies [Line Items]
Asset impairments for property and equipment	$ 3,900	3,938	1,484	265
U.S. | Oil And Gas Properties, Unproved
Schedule Of Significant Accounting Policies [Line Items]
Asset impairments for property and equipment		92	760	96
Egypt | Oil and gas proved property
Schedule Of Significant Accounting Policies [Line Items]
Asset impairments for property and equipment	354	374	0	63
Egypt | Oil And Gas Properties, Unproved
Schedule Of Significant Accounting Policies [Line Items]
Asset impairments for property and equipment		8	8	0
North Sea | Oil and gas proved property
Schedule Of Significant Accounting Policies [Line Items]
Asset impairments for property and equipment	$ 7	7	0	0
North Sea | Oil And Gas Properties, Unproved
Schedule Of Significant Accounting Policies [Line Items]
Asset impairments for property and equipment		$ 1	$ 0	$ 128