BUSINESS SEGMENTS (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Segment Reporting Information [Line Items]
Net interest income	$ 904	$ 836
Noninterest income	330	347
Total revenue	1,234	1,183
Noninterest expense	811	810
Profit before provision for credit losses	423	373
Provision for credit losses	91	58
Income before income tax expense	332	315
Income tax expense	109	106
Net income	223	209
Total average assets	138,780	133,325
Consumer Banking
Segment Reporting Information [Line Items]
Net interest income	581	533
Noninterest income	208	219
Total revenue	789	752
Noninterest expense	616	596
Profit before provision for credit losses	173	156
Provision for credit losses	63	63
Income before income tax expense	110	93
Income tax expense	39	32
Net income	71	61
Total average assets	55,116	51,602
Commercial Banking
Segment Reporting Information [Line Items]
Net interest income	300	276
Noninterest income	99	100
Total revenue	399	376
Noninterest expense	187	173
Profit before provision for credit losses	212	203
Provision for credit losses	9	(21)
Income before income tax expense	203	224
Income tax expense	70	77
Net income	133	147
Total average assets	45,304	41,606
Other
Segment Reporting Information [Line Items]
Net interest income	23	27
Noninterest income	23	28
Total revenue	46	55
Noninterest expense	8	41
Profit before provision for credit losses	38	14
Provision for credit losses	19	16
Income before income tax expense	19	(2)
Income tax expense	0	(3)
Net income	19	1
Total average assets	$ 38,360	$ 40,117