RECLASSIFICATIONS OUT OF ACCUMULATED OTHER COMPREHENSIVE LOSS - Effects to Net Income of Amounts Reclassified Out of OCI (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net interest income	$ 1,091	$ 1,005
Provision for credit losses	78	96
Noninterest income	371	379
Noninterest expense	883	854
Income before income tax expense	501	434
Income tax expense	113	114
NET INCOME	388	320
Amount Reclassified from AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net interest income	(2)	10
Noninterest income	7	3
Noninterest expense	4	5
Income tax expense	1	3
NET INCOME	$ 0	$ 5