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
	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule Of Significant Accounting Policies [Line Items]
Asset impairments for property and equipment	$ 9
Oil and gas proved property
Schedule Of Significant Accounting Policies [Line Items]
Asset impairments for property and equipment		$ 1,484	$ 328	$ 0
Oil And Gas Properties, Unproved
Schedule Of Significant Accounting Policies [Line Items]
Asset impairments for property and equipment		768	224	246
United States | Oil and gas proved property
Schedule Of Significant Accounting Policies [Line Items]
Asset impairments for property and equipment		1,484	265	0
United States | Oil And Gas Properties, Unproved
Schedule Of Significant Accounting Policies [Line Items]
Asset impairments for property and equipment		760	96	244
Egypt | Oil and gas proved property
Schedule Of Significant Accounting Policies [Line Items]
Asset impairments for property and equipment		0	63	0
Egypt | Oil And Gas Properties, Unproved
Schedule Of Significant Accounting Policies [Line Items]
Asset impairments for property and equipment		8	0	0
North Sea | Oil And Gas Properties, Unproved
Schedule Of Significant Accounting Policies [Line Items]
Asset impairments for property and equipment		0	128	0
Canada | Oil And Gas Properties, Unproved
Schedule Of Significant Accounting Policies [Line Items]
Asset impairments for property and equipment		$ 0	$ 0	$ 2