BUSINESS SEGMENTS (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Segment Reporting Information [Line Items]
Net interest income	$ 856	$ 820	$ 2,532	$ 2,461
Noninterest income	353	341	1,060	1,339
Total revenue	1,209	1,161	3,592	3,800
Noninterest expense	798	810	2,449	2,568
Profit (loss) before provision for credit losses	411	351	1,143	1,232
Provision for credit losses	76	77	211	247
Income before income tax expense	335	274	932	985
Income tax expense	115	85	313	317
NET INCOME	220	189	619	668
Total average assets	135,103	128,691	134,655	126,598
Consumer Banking
Segment Reporting Information [Line Items]
Net interest income	556	532	1,633	1,615
Noninterest income	235	226	684	681
Total revenue	791	758	2,317	2,296
Noninterest expense	623	609	1,832	1,902
Profit (loss) before provision for credit losses	168	149	485	394
Provision for credit losses	64	66	187	195
Income before income tax expense	104	83	298	199
Income tax expense	36	29	103	69
NET INCOME	68	54	195	130
Total average assets	53,206	49,012	52,438	48,398
Commercial Banking
Segment Reporting Information [Line Items]
Net interest income	299	270	861	790
Noninterest income	100	104	308	318
Total revenue	399	374	1,169	1,108
Noninterest expense	175	162	529	472
Profit (loss) before provision for credit losses	224	212	640	636
Provision for credit losses	3	0	(11)	(7)
Income before income tax expense	221	212	651	643
Income tax expense	76	73	224	222
NET INCOME	145	139	427	421
Total average assets	43,113	38,854	42,451	37,951
Other
Segment Reporting Information [Line Items]
Net interest income	1	18	38	56
Noninterest income	18	11	68	340
Total revenue	19	29	106	396
Noninterest expense	0	39	88	194
Profit (loss) before provision for credit losses	19	(10)	18	202
Provision for credit losses	9	11	35	59
Income before income tax expense	10	(21)	(17)	143
Income tax expense	3	(17)	(14)	26
NET INCOME	7	(4)	(3)	117
Total average assets	$ 38,784	$ 40,825	$ 39,766	$ 40,249