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		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net interest income	$ 1,145	$ 1,148	$ 3,471	$ 3,360
Provision for credit losses	101	78	283	241
Noninterest income	493	416	1,383	1,175
Noninterest expense	973	910	2,861	2,668
Income before income tax expense	564	576	1,710	1,626
Income tax expense	115	133	369	370
NET INCOME	449	443	1,341	1,256
Amount Reclassified from AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net interest income	(14)	(14)	(53)	(25)
Noninterest income	2	2	13	10
Noninterest expense	5	5	14	13
Income tax expense	(6)	(4)	(15)	(7)
NET INCOME	$ (11)	$ (13)	$ (39)	$ (21)