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		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net interest income	$ 923	$ 840	$ 1,827	$ 1,676
Provision for credit losses	90	77	181	135
Noninterest income	355	360	685	707
Noninterest expense	827	841	1,638	1,651
Income before income tax expense	361	282	693	597
Income tax expense	118	92	227	198
Net income	243	190	466	399
Amount Reclassified from AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net interest income	13	3	27	6
Noninterest income	(3)	7	5	14
Noninterest expense	4	4	8	7
Income tax expense	2	1	9	4
Net income	$ 4	$ 5	$ 15	$ 9