INCOME TAXES - Unrecognized Tax Benefit Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefit at beginning of year	$ 623	$ 491	$ 421
Change attributable to tax positions taken in prior years		37	12
Change attributable to tax positions taken in prior years	(13)
Change attributable to tax positions taken during the current period	13	148	87
Decrease attributable to settlements with taxing authorities	(54)	(53)	(28)
Decrease attributable to lapse of statute of limitations			(1)
Unrecognized tax benefit at end of year	$ 569	$ 623	$ 491