INCOME AND MINING TAXES - Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation Of Unrecognized Tax Benefits
Total amount of gross unrecognized tax benefits at beginning of year	$ 43	$ 68	$ 68
Additions due to acquisition	350
Decreases for tax positions of prior years			(27)
Additions for tax positions of prior years	1	1
Additions for tax positions of current year	34	2	30
Reductions due to settlements with taxing authorities	(102)	(28)
Reductions due to lapse of statute of limitations			(3)
Total amount of gross unrecognized tax benefits at end of year	$ 326	$ 43	$ 68