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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net interest income	$ 1,062	$ 945	$ 3,093	$ 2,772
Provision for credit losses	72	86	238	267
Noninterest income	381	435	1,130	1,120
Noninterest expense	858	867	2,576	2,505
Income before income tax expense	513	427	1,409	1,120
Income tax expense	165	130	423	357
NET INCOME	348	297	986	763
Amount Reclassified from AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net interest income	4	15	21	42
Noninterest income	1	(8)	3	(3)
Noninterest expense	5	4	14	12
Income tax expense	0	1	3	10
NET INCOME	$ 0	$ 2	$ 7	$ 17