RECLASSIFICATIONS OUT OF ACCUMULATED OTHER COMPREHENSIVE INCOME - Effects to Net Income of Amounts Reclassified Out of OCI (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net interest income	$ 840	$ 833	$ 1,676	$ 1,641
Provision for credit losses	77	49	135	170
Noninterest income	360	640	707	998
Noninterest expense	841	948	1,651	1,758
Income before income tax expense	282	476	597	711
Income tax expense	92	163	198	232
NET INCOME	190	313	399	479
Amount Reclassified from OCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net interest income	840	833	1,676	1,641
Provision for credit losses	77	49	135	170
Noninterest income	360	640	707	998
Noninterest expense	841	948	1,651	1,758
Income before income tax expense	282	476	597	711
Income tax expense	92	163	198	232
NET INCOME	190	313	399	479
Amount Reclassified from AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net interest income	3	(9)	6	(20)
Noninterest income	7	(2)	14	19
Noninterest expense	4	1	7	3
Income tax expense	1	(3)	4	(1)
NET INCOME	$ 5	$ (9)	$ 9	$ (3)