INCOME TAXES - COMPONENTS OF DEFERRED TAX ASSETS AND LIABILITIES (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Deferred tax liabilities
Property, plant and equipment differences	$ (12,375)	$ (2,089)
Equity investments, partnerships and foreign subsidiaries	(989)	(161)
Gross long-term deferred tax liabilities	(13,364)	(2,250)
Deferred tax assets
Environmental reserves	261	195
Postretirement benefit accruals	441	176
Deferred compensation and benefits	266	170
Asset retirement obligations	906	280
Foreign tax credit carryforwards	4,379	2,356
General business credit carryforwards	443	429
Net operating loss carryforward	692	29
Interest expense carryforward	492	0
All other	782	111
Gross long-term deferred tax assets	8,662	3,746
Valuation allowance	(4,959)	(2,403)
Net long-term deferred tax assets	3,703	1,343
Less: Foreign deferred tax asset in long-term receivables and other assets, net	(56)	0
Total deferred income taxes, net	$ (9,717)	$ (907)