BUSINESS SEGMENTS (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Segment Reporting Information [Line Items]
Net interest income	$ 923	$ 840	$ 1,827	$ 1,676
Noninterest income	355	360	685	707
Total revenue	1,278	1,200	2,512	2,383
Noninterest expense	827	841	1,638	1,651
Profit before provision for credit losses	451	359	874	732
Provision for credit losses	90	77	181	135
Income before income tax expense	361	282	693	597
Income tax expense	118	92	227	198
NET INCOME	243	190	466	399
Total average assets	142,179	135,521	140,479	134,429
Consumer Banking
Segment Reporting Information [Line Items]
Net interest income	602	544	1,183	1,077
Noninterest income	219	230	427	449
Total revenue	821	774	1,610	1,526
Noninterest expense	632	613	1,248	1,209
Profit before provision for credit losses	189	161	362	317
Provision for credit losses	49	60	112	123
Income before income tax expense	140	101	250	194
Income tax expense	50	35	89	67
NET INCOME	90	66	161	127
Total average assets	55,660	52,489	55,388	52,048
Commercial Banking
Segment Reporting Information [Line Items]
Net interest income	314	286	614	562
Noninterest income	122	108	221	208
Total revenue	436	394	835	770
Noninterest expense	186	181	373	354
Profit before provision for credit losses	250	213	462	416
Provision for credit losses	(1)	7	8	(14)
Income before income tax expense	251	206	454	430
Income tax expense	87	71	157	148
NET INCOME	164	135	297	282
Total average assets	47,388	42,617	46,346	42,114
Other
Segment Reporting Information [Line Items]
Net interest income	7	10	30	37
Noninterest income	14	22	37	50
Total revenue	21	32	67	87
Noninterest expense	9	47	17	88
Profit before provision for credit losses	12	(15)	50	(1)
Provision for credit losses	42	10	61	26
Income before income tax expense	(30)	(25)	(11)	(27)
Income tax expense	(19)	(14)	(19)	(17)
NET INCOME	(11)	(11)	8	(10)
Total average assets	$ 39,131	$ 40,415	$ 38,745	$ 40,267