ALLOWANCE FOR CREDIT LOSSES, NONACCRUAL LOANS AND LEASES, AND CONCENTRATIONS OF CREDIT RISK - Amortized Cost Basis by Credit Quality Indicator (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 156,140	$ 128,163
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	11,555	13,660
Year two	16,273	6,289
Year three	6,802	7,499
Year four	6,933	4,775
Year five	4,593	2,327
Prior to year five	7,795	3,878
Within the Revolving Period	26,970	21,777
Converted to Term	193	145
Total	81,114	60,350
Commercial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	11,300	13,431
Year two	15,857	6,015
Year three	6,410	6,914
Year four	5,980	4,184
Year five	4,025	2,118
Prior to year five	6,734	3,441
Within the Revolving Period	26,060	20,857
Converted to Term	176	125
Total	76,542	57,085
Commercial | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	58	102
Year two	247	128
Year three	244	268
Year four	417	219
Year five	222	71
Prior to year five	267	159
Within the Revolving Period	330	316
Converted to Term	0	1
Total	1,785	1,264
Commercial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	187	125
Year two	159	128
Year three	127	308
Year four	532	350
Year five	307	128
Prior to year five	768	260
Within the Revolving Period	492	530
Converted to Term	15	17
Total	2,587	1,846
Commercial | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	10	2
Year two	10	18
Year three	21	9
Year four	4	22
Year five	39	10
Prior to year five	26	18
Within the Revolving Period	88	74
Converted to Term	2	2
Total	200	155
Commercial | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	6,495	10,363
Year two	9,339	3,528
Year three	2,749	3,978
Year four	2,921	2,501
Year five	1,788	1,527
Prior to year five	2,789	2,144
Within the Revolving Period	24,718	20,317
Converted to Term	190	142
Total	50,989	44,500
Commercial | Commercial and industrial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	6,375	10,218
Year two	8,966	3,336
Year three	2,479	3,599
Year four	2,441	2,284
Year five	1,587	1,426
Prior to year five	2,404	1,863
Within the Revolving Period	23,840	19,406
Converted to Term	173	122
Total	48,265	42,254
Commercial | Commercial and industrial | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	55	47
Year two	206	71
Year three	134	155
Year four	139	114
Year five	71	41
Prior to year five	123	64
Within the Revolving Period	321	316
Converted to Term	0	1
Total	1,049	809
Commercial | Commercial and industrial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	55	97
Year two	158	112
Year three	124	215
Year four	337	81
Year five	91	50
Prior to year five	238	201
Within the Revolving Period	469	521
Converted to Term	15	17
Total	1,487	1,294
Commercial | Commercial and industrial | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	10	1
Year two	9	9
Year three	12	9
Year four	4	22
Year five	39	10
Prior to year five	24	16
Within the Revolving Period	88	74
Converted to Term	2	2
Total	188	143
Commercial | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	4,885	2,839
Year two	6,548	2,468
Year three	3,793	3,382
Year four	3,896	2,123
Year five	2,670	731
Prior to year five	4,634	1,258
Within the Revolving Period	2,252	1,460
Converted to Term	3	3
Total	28,681	14,264
Commercial | Commercial real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	4,752	2,766
Year two	6,514	2,417
Year three	3,674	3,181
Year four	3,431	1,756
Year five	2,305	626
Prior to year five	3,962	1,119
Within the Revolving Period	2,220	1,451
Converted to Term	3	3
Total	26,861	13,319
Commercial | Commercial real estate | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	1	45
Year two	32	42
Year three	110	113
Year four	273	100
Year five	149	27
Prior to year five	140	79
Within the Revolving Period	9	0
Converted to Term	0	0
Total	714	406
Commercial | Commercial real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	132	27
Year two	1	0
Year three	0	88
Year four	192	267
Year five	216	78
Prior to year five	530	59
Within the Revolving Period	23	9
Converted to Term	0	0
Total	1,094	528
Commercial | Commercial real estate | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0	1
Year two	1	9
Year three	9	0
Year four	0	0
Year five	0	0
Prior to year five	2	1
Within the Revolving Period	0	0
Converted to Term	0	0
Total	12	11
Commercial | Leases
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	175	458
Year two	386	293
Year three	260	139
Year four	116	151
Year five	135	69
Prior to year five	372	476
Within the Revolving Period	0	0
Converted to Term	0	0
Total	1,444	1,586
Commercial | Leases | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	173	447
Year two	377	262
Year three	257	134
Year four	108	144
Year five	133	66
Prior to year five	368	459
Within the Revolving Period	0	0
Converted to Term	0	0
Total	1,416	1,512
Commercial | Leases | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	2	10
Year two	9	15
Year three	0	0
Year four	5	5
Year five	2	3
Prior to year five	4	16
Within the Revolving Period	0	0
Converted to Term	0	0
Total	22	49
Commercial | Leases | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0	1
Year two	0	16
Year three	3	5
Year four	3	2
Year five	0	0
Prior to year five	0	0
Within the Revolving Period	0	0
Converted to Term	0	0
Total	6	24
Commercial | Leases | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
Prior to year five	0	1
Within the Revolving Period	0	0
Converted to Term	0	0
Total	0	1
Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	9,902	19,683
Year two	19,051	13,715
Year three	11,621	7,020
Year four	5,580	3,366
Year five	2,650	3,083
Prior to year five	9,865	7,094
Within the Revolving Period	15,204	12,688
Converted to Term	1,153	1,164
Total	75,026	67,813
Retail | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	4,646	7,700
Year two	9,103	5,669
Year three	5,609	2,637
Year four	2,488	995
Year five	1,041	1,468
Prior to year five	6,661	4,353
Within the Revolving Period	0	0
Converted to Term	0	0
Total	29,548	22,822
Retail | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	6	0
Year two	9	9
Year three	9	43
Year four	38	66
Year five	60	63
Prior to year five	530	589
Within the Revolving Period	11,892	10,100
Converted to Term	1,140	1,145
Total	13,684	12,015
Retail | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	3,054	7,469
Year two	5,620	3,227
Year three	2,264	2,065
Year four	1,337	1,000
Year five	577	561
Prior to year five	303	227
Within the Revolving Period	0	0
Converted to Term	0	0
Total	13,155	14,549
Retail | Education
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	1,532	3,487
Year two	3,712	3,899
Year three	3,244	1,798
Year four	1,468	1,071
Year five	858	890
Prior to year five	2,280	1,852
Within the Revolving Period	0	0
Converted to Term	0	0
Total	13,094	12,997
Retail | Other retail
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	664	1,027
Year two	607	911
Year three	495	477
Year four	249	234
Year five	114	101
Prior to year five	91	73
Within the Revolving Period	3,312	2,588
Converted to Term	13	19
Total	5,545	5,430
Greater than 800 | Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	2,723	5,912
Year two	7,854	5,833
Year three	5,411	2,735
Year four	2,299	1,170
Year five	942	1,323
Prior to year five	4,231	3,239
Within the Revolving Period	5,326	4,780
Converted to Term	287	281
Total	29,073	25,273
Greater than 800 | Retail | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	1,501	2,431
Year two	4,470	3,017
Year three	3,068	1,230
Year four	1,142	342
Year five	331	672
Prior to year five	2,878	2,139
Within the Revolving Period	0	0
Converted to Term	0	0
Total	13,390	9,831
Greater than 800 | Retail | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	2	0
Year two	3	2
Year three	2	5
Year four	5	5
Year five	6	3
Prior to year five	111	134
Within the Revolving Period	4,866	4,394
Converted to Term	287	281
Total	5,282	4,824
Greater than 800 | Retail | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	597	1,887
Year two	1,516	829
Year three	643	538
Year four	369	244
Year five	147	148
Prior to year five	78	57
Within the Revolving Period	0	0
Converted to Term	0	0
Total	3,350	3,703
Greater than 800 | Retail | Education
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	474	1,361
Year two	1,714	1,771
Year three	1,582	840
Year four	719	514
Year five	426	470
Prior to year five	1,131	880
Within the Revolving Period	0	0
Converted to Term	0	0
Total	6,046	5,836
Greater than 800 | Retail | Other retail
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	149	233
Year two	151	214
Year three	116	122
Year four	64	65
Year five	32	30
Prior to year five	33	29
Within the Revolving Period	460	386
Converted to Term	0	0
Total	1,005	1,079
740-799 | Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	4,145	8,311
Year two	6,899	4,801
Year three	3,911	2,210
Year four	1,721	994
Year five	794	836
Prior to year five	2,832	1,806
Within the Revolving Period	5,214	4,278
Converted to Term	287	280
Total	25,803	23,516
740-799 | Retail | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	2,362	4,015
Year two	3,464	1,876
Year three	1,818	746
Year four	716	246
Year five	300	360
Prior to year five	1,965	1,086
Within the Revolving Period	0	0
Converted to Term	0	0
Total	10,625	8,329
740-799 | Retail | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	3	0
Year two	4	1
Year three	2	4
Year four	5	5
Year five	6	7
Prior to year five	108	122
Within the Revolving Period	4,282	3,514
Converted to Term	286	278
Total	4,696	3,931
740-799 | Retail | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	921	2,418
Year two	1,783	1,051
Year three	727	615
Year four	397	288
Year five	164	156
Prior to year five	81	58
Within the Revolving Period	0	0
Converted to Term	0	0
Total	4,073	4,586
740-799 | Retail | Education
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	665	1,555
Year two	1,456	1,577
Year three	1,209	672
Year four	517	371
Year five	284	275
Prior to year five	647	514
Within the Revolving Period	0	0
Converted to Term	0	0
Total	4,778	4,964
740-799 | Retail | Other retail
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	194	323
Year two	192	296
Year three	155	173
Year four	86	84
Year five	40	38
Prior to year five	31	26
Within the Revolving Period	932	764
Converted to Term	1	2
Total	1,631	1,706
680-739 | Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	2,024	3,842
Year two	2,894	2,114
Year three	1,552	1,193
Year four	851	596
Year five	436	441
Prior to year five	1,426	1,041
Within the Revolving Period	3,054	2,447
Converted to Term	240	248
Total	12,477	11,922
680-739 | Retail | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	669	1,116
Year two	949	572
Year three	519	335
Year four	297	152
Year five	161	172
Prior to year five	922	585
Within the Revolving Period	0	0
Converted to Term	0	0
Total	3,517	2,932
680-739 | Retail | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	1	0
Year two	1	1
Year three	2	7
Year four	7	14
Year five	13	16
Prior to year five	123	134
Within the Revolving Period	2,106	1,738
Converted to Term	236	243
Total	2,489	2,153
680-739 | Retail | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	866	1,968
Year two	1,342	827
Year three	527	500
Year four	300	234
Year five	127	123
Prior to year five	63	48
Within the Revolving Period	0	0
Converted to Term	0	0
Total	3,225	3,700
680-739 | Retail | Education
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	333	512
Year two	454	474
Year three	375	229
Year four	182	140
Year five	108	107
Prior to year five	300	262
Within the Revolving Period	0	0
Converted to Term	0	0
Total	1,752	1,724
680-739 | Retail | Other retail
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	155	246
Year two	148	240
Year three	129	122
Year four	65	56
Year five	27	23
Prior to year five	18	12
Within the Revolving Period	948	709
Converted to Term	4	5
Total	1,494	1,413
620-679 | Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	771	1,339
Year two	989	696
Year three	484	517
Year four	388	296
Year five	230	231
Prior to year five	693	523
Within the Revolving Period	925	662
Converted to Term	163	172
Total	4,643	4,436
620-679 | Retail | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	104	111
Year two	156	130
Year three	125	161
Year four	164	93
Year five	101	107
Prior to year five	442	276
Within the Revolving Period	0	0
Converted to Term	0	0
Total	1,092	878
620-679 | Retail | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0	0
Year two	1	3
Year three	1	11
Year four	9	19
Year five	16	17
Prior to year five	99	112
Within the Revolving Period	498	363
Converted to Term	159	167
Total	783	692
620-679 | Retail | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	526	1,029
Year two	676	378
Year three	234	257
Year four	155	131
Year five	74	72
Prior to year five	40	32
Within the Revolving Period	0	0
Converted to Term	0	0
Total	1,705	1,899
620-679 | Retail | Education
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	44	50
Year two	74	66
Year three	60	45
Year four	37	34
Year five	29	28
Prior to year five	106	99
Within the Revolving Period	0	0
Converted to Term	0	0
Total	350	322
620-679 | Retail | Other retail
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	97	149
Year two	82	119
Year three	64	43
Year four	23	19
Year five	10	7
Prior to year five	6	4
Within the Revolving Period	427	299
Converted to Term	4	5
Total	713	645
Less than 620 | Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	180	225
Year two	412	258
Year three	258	364
Year four	317	310
Year five	245	252
Prior to year five	621	423
Within the Revolving Period	307	191
Converted to Term	175	182
Total	2,515	2,205
Less than 620 | Retail | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	8	24
Year two	62	66
Year three	77	164
Year four	166	162
Year five	145	157
Prior to year five	438	257
Within the Revolving Period	0	0
Converted to Term	0	0
Total	896	830
Less than 620 | Retail | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0	0
Year two	0	2
Year three	2	16
Year four	12	23
Year five	19	20
Prior to year five	89	87
Within the Revolving Period	140	91
Converted to Term	172	176
Total	434	415
Less than 620 | Retail | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	141	164
Year two	303	142
Year three	133	155
Year four	116	103
Year five	65	62
Prior to year five	41	32
Within the Revolving Period	0	0
Converted to Term	0	0
Total	799	658
Less than 620 | Retail | Education
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	4	5
Year two	14	11
Year three	18	12
Year four	12	12
Year five	11	10
Prior to year five	50	45
Within the Revolving Period	0	0
Converted to Term	0	0
Total	109	95
Less than 620 | Retail | Other retail
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	27	32
Year two	33	37
Year three	28	17
Year four	11	10
Year five	5	3
Prior to year five	3	2
Within the Revolving Period	167	100
Converted to Term	3	6
Total	277	207
No FICO available | Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	59	54
Year two	3	13
Year three	5	1
Year four	4	0
Year five	3	0
Prior to year five	62	62
Within the Revolving Period	378	330
Converted to Term	1	1
Total	515	461
No FICO available | Retail | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	2	3
Year two	2	8
Year three	2	1
Year four	3	0
Year five	3	0
Prior to year five	16	10
Within the Revolving Period	0	0
Converted to Term	0	0
Total	28	22
No FICO available | Retail | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	3	3
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
Prior to year five	0	0
Within the Revolving Period	0	0
Converted to Term	0	0
Total	3	3
No FICO available | Retail | Education
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	12	4
Year two	0	0
Year three	0	0
Year four	1	0
Year five	0	0
Prior to year five	46	52
Within the Revolving Period	0	0
Converted to Term	0	0
Total	59	56
No FICO available | Retail | Other retail
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	42	44
Year two	1	5
Year three	3	0
Year four	0	0
Year five	0	0
Prior to year five	0	0
Within the Revolving Period	378	330
Converted to Term	1	1
Total	$ 425	$ 380