INCOME TAXES - Uncertain Tax Positions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Uncertain Tax Positions
Balance at the beginning of the period	$ 58	$ 54
Total balance at beginning of the period	67	62
Current year tax positions: Additions	14	13
Current year tax positions: Reductions	(1)	(1)
Prior year tax positions: Additions	1	1
Prior year tax positions: Reductions		(1)
Lapse of applicable statute of limitations	(9)	(8)
Balance at the end of the period	63	58
Total balance at the end of the period	73	67
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense [Abstract]
Interest and penalties at period start	9	8
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	1	1
Interest and penalties at period end	$ 10	$ 9