BUSINESS SEGMENTS (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Net interest income	$ 1,026	$ 923	$ 2,031	$ 1,827
Noninterest income	370	355	749	685
Total revenue	1,396	1,278	2,780	2,512
Noninterest expense	864	827	1,718	1,638
Profit before provision for credit losses	532	451	1,062	874
Provision for credit losses	70	90	166	181
Income before income tax expense	462	361	896	693
Income tax expense	144	118	258	227
NET INCOME	318	243	638	466
Total average assets	149,878	142,179	149,335	140,479
Consumer Banking
Segment Reporting Information [Line Items]
Net interest income	657	602	1,295	1,183
Noninterest income	229	219	449	427
Total revenue	886	821	1,744	1,610
Noninterest expense	644	632	1,291	1,248
Profit before provision for credit losses	242	189	453	362
Provision for credit losses	60	49	124	112
Income before income tax expense	182	140	329	250
Income tax expense	64	50	116	89
NET INCOME	118	90	213	161
Total average assets	59,244	55,660	58,954	55,388
Commercial Banking
Segment Reporting Information [Line Items]
Net interest income	344	314	690	614
Noninterest income	130	122	264	221
Total revenue	474	436	954	835
Noninterest expense	192	186	382	373
Profit before provision for credit losses	282	250	572	462
Provision for credit losses	1	(1)	20	8
Income before income tax expense	281	251	552	454
Income tax expense	94	87	185	157
NET INCOME	187	164	367	297
Total average assets	49,731	47,388	49,488	46,346
Other
Segment Reporting Information [Line Items]
Net interest income	25	7	46	30
Noninterest income	11	14	36	37
Total revenue	36	21	82	67
Noninterest expense	28	9	45	17
Profit before provision for credit losses	8	12	37	50
Provision for credit losses	9	42	22	61
Income before income tax expense	(1)	(30)	15	(11)
Income tax expense	(14)	(19)	(43)	(19)
NET INCOME	13	(11)	58	8
Total average assets	$ 40,903	$ 39,131	$ 40,893	$ 38,745