DERIVATIVES - Schedule of Fair Value Hedges (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Derivative	$ 66	$ 65	$ 32
Hedge of interest rate risk | Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative	(26)	(6)	(2)
Hedged Item	27	5	2
Hedge Ineffectiveness	$ 1	$ (1)	$ 0