INCOME TAXES (Components of deferred tax assets and liabilities) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Loss Carryforwards [Line Items]
Foreign	$ 2,882	$ 1,707	$ 461
U.S.	20	(5,179)	$ (14,589)
Deferred tax assets:
Foreign tax credits	2,129	2,094
Accrued expenses	789	923
Oil and gas properties	236	346
AMT credits	490	444
Net operating losses	2,043	2,898
Employee benefit plans	248	403
Other	259	485
Deferred tax assets	5,704	7,593
Valuation allowances	(4,575)	(6,058)
Net deferred tax assets	1,129	1,535
Deferred tax liabilities:
Property, plant, equipment and mine development costs	(3,710)	(4,326)
Undistributed earnings	(811)	(779)
Other	(226)	(195)
Total deferred tax liabilities	(4,747)	(5,300)
Net deferred tax liabilities	(3,618)	$ (3,765)
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
U.S.	5,300
Deferred tax assets:
Valuation allowances	(280)
Foreign Tax Authority
Operating Loss Carryforwards [Line Items]
Foreign	5,300
Deferred tax assets:
Foreign tax credits	$ 1,100