INCOME TAXES - Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of year	$ 82	$ 24	$ 26	$ 15
Additions based on tax positions related to prior year	49	0	0
Additions based on tax positions related to the current year	9	0	12
Reductions for tax positions of prior years	0	(2)	(1)
Balance at end of year	$ 82	$ 24	$ 26	$ 15