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, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net interest income	$ 856	$ 820	$ 2,532	$ 2,461
Provision for credit losses	76	77	211	247
Noninterest income	353	341	1,060	1,339
Noninterest expense	798	810	2,449	2,568
Income before income tax expense	335	274	932	985
Income tax expense	115	85	313	317
NET INCOME	220	189	619	668
Amount Reclassified from OCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net interest income	856	820	2,532	2,461
Provision for credit losses	76	77	211	247
Noninterest income	353	341	1,060	1,339
Noninterest expense	798	810	2,449	2,568
Income before income tax expense	335	274	932	985
Income tax expense	115	85	313	317
NET INCOME	220	189	619	668
Amount Reclassified from AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net interest income	7	(5)	13	(25)
Noninterest income	0	1	14	20
Noninterest expense	3	(52)	10	(49)
Income tax expense	3	16	7	15
NET INCOME	$ 1	$ 32	$ 10	$ 29