BUSINESS SEGMENTS (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information [Line Items]
Net interest income	$ 1,005	$ 904
Noninterest income	379	330
Total revenue	1,384	1,234
Noninterest expense	854	811
Profit before provision for credit losses	530	423
Provision for credit losses	96	91
Income before income tax expense	434	332
Income tax expense	114	109
NET INCOME	320	223
Total average assets	148,786	138,780
Consumer Banking
Segment Reporting Information [Line Items]
Net interest income	638	581
Noninterest income	220	208
Total revenue	858	789
Noninterest expense	647	616
Profit before provision for credit losses	211	173
Provision for credit losses	64	63
Income before income tax expense	147	110
Income tax expense	52	39
NET INCOME	95	71
Total average assets	58,660	55,116
Commercial Banking
Segment Reporting Information [Line Items]
Net interest income	346	300
Noninterest income	134	99
Total revenue	480	399
Noninterest expense	190	187
Profit before provision for credit losses	290	212
Provision for credit losses	19	9
Income before income tax expense	271	203
Income tax expense	91	70
NET INCOME	180	133
Total average assets	49,243	45,304
Other
Segment Reporting Information [Line Items]
Net interest income	21	23
Noninterest income	25	23
Total revenue	46	46
Noninterest expense	17	8
Profit before provision for credit losses	29	38
Provision for credit losses	13	19
Income before income tax expense	16	19
Income tax expense	(29)	0
NET INCOME	45	19
Total average assets	$ 40,883	$ 38,360