RECLASSIFICATIONS OUT OF ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Effects to Net Income of Amounts Reclassified Out of OCI (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net interest income	$ 1,160	$ 1,091
Provision for credit losses	85	78
Noninterest income	428	371
Noninterest expense	937	883
Income before income tax expense	566	501
Income tax expense	127	113
NET INCOME	439	388
Amount Reclassified from AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net interest income	(20)	(2)
Noninterest income	7	7
Noninterest expense	5	4
Income tax expense	(5)	1
NET INCOME	$ (13)	$ 0