INCOME TAXES - RECONCILIATION OF UNRECOGNIZED TAX BENEFITS (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance, at beginning of period	$ 2,173	$ 0	$ 22
Increase related to Anadarko Acquisition	0	2,143	0
Increases related to current-year positions	14	30	0
Settlements	(42)	0	(22)
Reductions for tax positions of prior years	(100)	0	0
Balance, at end of period	$ 2,045	$ 2,173	$ 0