BUSINESS SEGMENTS (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting Information [Line Items]
Net interest income	$ 945	$ 856	$ 2,772	$ 2,532
Noninterest income	435	353	1,120	1,060
Total revenue	1,380	1,209	3,892	3,592
Noninterest expense	867	798	2,505	2,449
Profit before provision for credit losses	513	411	1,387	1,143
Provision for credit losses	86	76	267	211
Income before income tax expense	427	335	1,120	932
Income tax expense	130	115	357	313
NET INCOME	297	220	763	619
Total average assets	144,399	135,103	141,795	134,655
Consumer Banking
Segment Reporting Information [Line Items]
Net interest income	621	556	1,804	1,633
Noninterest income	229	235	656	684
Total revenue	850	791	2,460	2,317
Noninterest expense	650	623	1,898	1,832
Profit before provision for credit losses	200	168	562	485
Provision for credit losses	57	64	169	187
Income before income tax expense	143	104	393	298
Income tax expense	51	36	140	103
NET INCOME	92	68	253	195
Total average assets	56,689	53,206	55,825	52,438
Commercial Banking
Segment Reporting Information [Line Items]
Net interest income	327	299	941	861
Noninterest income	123	100	344	308
Total revenue	450	399	1,285	1,169
Noninterest expense	181	175	554	529
Profit before provision for credit losses	269	224	731	640
Provision for credit losses	19	3	27	(11)
Income before income tax expense	250	221	704	651
Income tax expense	88	76	245	224
NET INCOME	162	145	459	427
Total average assets	47,902	43,113	46,869	42,451
Other
Segment Reporting Information [Line Items]
Net interest income	(3)	1	27	38
Noninterest income	83	18	120	68
Total revenue	80	19	147	106
Noninterest expense	36	0	53	88
Profit before provision for credit losses	44	19	94	18
Provision for credit losses	10	9	71	35
Income before income tax expense	34	10	23	(17)
Income tax expense	(9)	3	(28)	(14)
NET INCOME	43	7	51	(3)
Total average assets	$ 39,808	$ 38,784	$ 39,101	$ 39,766