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, 2016	Mar. 31, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net interest income	$ 904	$ 836
Provision for credit losses	91	58
Noninterest income	330	347
Noninterest expense	811	810
Income before income tax expense	332	315
Income tax expense	109	106
Net income	223	209
Amount Reclassified from OCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net interest income	904	836
Provision for credit losses	91	58
Noninterest income	330	347
Noninterest expense	811	810
Income before income tax expense	332	315
Income tax expense	109	106
Net income	223	209
Amount Reclassified from AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net interest income	14	3
Noninterest income	8	7
Noninterest expense	4	3
Income tax expense	7	3
Net income	$ 11	$ 4