ALLOWANCE FOR CREDIT LOSSES, NONACCRUAL LOANS AND LEASES, AND CONCENTRATIONS OF CREDIT RISK - Amortized Cost Basis by Credit Quality Indicator (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 156,662	$ 128,163
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	14,715	13,660
Year two	15,843	6,289
Year three	6,633	7,499
Year four	6,280	4,775
Year five	4,245	2,327
Prior to year five	7,076	3,878
Within the Revolving Period	27,221	21,777
Converted to Term	167	145
Total	82,180	60,350
Commercial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	14,334	13,431
Year two	15,274	6,015
Year three	6,113	6,914
Year four	5,239	4,184
Year five	3,607	2,118
Prior to year five	5,833	3,441
Within the Revolving Period	26,099	20,857
Converted to Term	151	125
Total	76,650	57,085
Commercial | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	129	102
Year two	313	128
Year three	225	268
Year four	470	219
Year five	148	71
Prior to year five	269	159
Within the Revolving Period	426	316
Converted to Term	0	1
Total	1,980	1,264
Commercial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	242	125
Year two	240	128
Year three	285	308
Year four	511	350
Year five	449	128
Prior to year five	959	260
Within the Revolving Period	620	530
Converted to Term	14	17
Total	3,320	1,846
Commercial | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	10	2
Year two	16	18
Year three	10	9
Year four	60	22
Year five	41	10
Prior to year five	15	18
Within the Revolving Period	76	74
Converted to Term	2	2
Total	230	155
Commercial | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	8,588	10,363
Year two	8,890	3,528
Year three	2,548	3,978
Year four	2,408	2,501
Year five	1,522	1,527
Prior to year five	2,468	2,144
Within the Revolving Period	25,248	20,317
Converted to Term	164	142
Total	51,836	44,500
Commercial | Commercial and industrial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	8,304	10,218
Year two	8,469	3,336
Year three	2,224	3,599
Year four	2,074	2,284
Year five	1,334	1,426
Prior to year five	1,952	1,863
Within the Revolving Period	24,211	19,406
Converted to Term	148	122
Total	48,716	42,254
Commercial | Commercial and industrial | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	124	47
Year two	189	71
Year three	120	155
Year four	74	114
Year five	48	41
Prior to year five	153	64
Within the Revolving Period	364	316
Converted to Term	0	1
Total	1,072	809
Commercial | Commercial and industrial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	150	97
Year two	218	112
Year three	203	215
Year four	255	81
Year five	99	50
Prior to year five	349	201
Within the Revolving Period	597	521
Converted to Term	14	17
Total	1,885	1,294
Commercial | Commercial and industrial | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	10	1
Year two	14	9
Year three	1	9
Year four	5	22
Year five	41	10
Prior to year five	14	16
Within the Revolving Period	76	74
Converted to Term	2	2
Total	163	143
Commercial | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	5,860	2,839
Year two	6,581	2,468
Year three	3,830	3,382
Year four	3,764	2,123
Year five	2,594	731
Prior to year five	4,260	1,258
Within the Revolving Period	1,973	1,460
Converted to Term	3	3
Total	28,865	14,264
Commercial | Commercial real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	5,767	2,766
Year two	6,442	2,417
Year three	3,639	3,181
Year four	3,066	1,756
Year five	2,145	626
Prior to year five	3,536	1,119
Within the Revolving Period	1,888	1,451
Converted to Term	3	3
Total	26,486	13,319
Commercial | Commercial real estate | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	1	45
Year two	119	42
Year three	103	113
Year four	390	100
Year five	99	27
Prior to year five	113	79
Within the Revolving Period	62	0
Converted to Term	0	0
Total	887	406
Commercial | Commercial real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	92	27
Year two	18	0
Year three	79	88
Year four	253	267
Year five	350	78
Prior to year five	610	59
Within the Revolving Period	23	9
Converted to Term	0	0
Total	1,425	528
Commercial | Commercial real estate | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0	1
Year two	2	9
Year three	9	0
Year four	55	0
Year five	0	0
Prior to year five	1	1
Within the Revolving Period	0	0
Converted to Term	0	0
Total	67	11
Commercial | Leases
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	267	458
Year two	372	293
Year three	255	139
Year four	108	151
Year five	129	69
Prior to year five	348	476
Within the Revolving Period	0	0
Converted to Term	0	0
Total	1,479	1,586
Commercial | Leases | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	263	447
Year two	363	262
Year three	250	134
Year four	99	144
Year five	128	66
Prior to year five	345	459
Within the Revolving Period	0	0
Converted to Term	0	0
Total	1,448	1,512
Commercial | Leases | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	4	10
Year two	5	15
Year three	2	0
Year four	6	5
Year five	1	3
Prior to year five	3	16
Within the Revolving Period	0	0
Converted to Term	0	0
Total	21	49
Commercial | Leases | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0	1
Year two	4	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	10	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	11,158	19,683
Year two	18,251	13,715
Year three	11,083	7,020
Year four	5,223	3,366
Year five	2,457	3,083
Prior to year five	9,401	7,094
Within the Revolving Period	15,803	12,688
Converted to Term	1,106	1,164
Total	74,482	67,813
Retail | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	5,421	7,700
Year two	9,071	5,669
Year three	5,519	2,637
Year four	2,432	995
Year five	1,017	1,468
Prior to year five	6,461	4,353
Within the Revolving Period	0	0
Converted to Term	0	0
Total	29,921	22,822
Retail | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	7	0
Year two	9	9
Year three	8	43
Year four	36	66
Year five	57	63
Prior to year five	496	589
Within the Revolving Period	12,340	10,100
Converted to Term	1,090	1,145
Total	14,043	12,015
Retail | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	3,276	7,469
Year two	5,141	3,227
Year three	2,028	2,065
Year four	1,160	1,000
Year five	474	561
Prior to year five	213	227
Within the Revolving Period	0	0
Converted to Term	0	0
Total	12,292	14,549
Retail | Education
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	1,712	3,487
Year two	3,586	3,899
Year three	3,131	1,798
Year four	1,400	1,071
Year five	820	890
Prior to year five	2,159	1,852
Within the Revolving Period	0	0
Converted to Term	0	0
Total	12,808	12,997
Retail | Other retail
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	742	1,027
Year two	444	911
Year three	397	477
Year four	195	234
Year five	89	101
Prior to year five	72	73
Within the Revolving Period	3,463	2,588
Converted to Term	16	19
Total	5,418	5,430
Greater than 800 | Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	3,516	5,912
Year two	8,226	5,833
Year three	5,389	2,735
Year four	2,251	1,170
Year five	924	1,323
Prior to year five	4,340	3,239
Within the Revolving Period	5,449	4,780
Converted to Term	267	281
Total	30,362	25,273
Greater than 800 | Retail | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	2,132	2,431
Year two	4,943	3,017
Year three	3,143	1,230
Year four	1,180	342
Year five	363	672
Prior to year five	3,081	2,139
Within the Revolving Period	0	0
Converted to Term	0	0
Total	14,842	9,831
Greater than 800 | Retail | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	4	0
Year two	5	2
Year three	2	5
Year four	5	5
Year five	6	3
Prior to year five	110	134
Within the Revolving Period	4,958	4,394
Converted to Term	267	281
Total	5,357	4,824
Greater than 800 | Retail | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	650	1,887
Year two	1,453	829
Year three	584	538
Year four	324	244
Year five	120	148
Prior to year five	54	57
Within the Revolving Period	0	0
Converted to Term	0	0
Total	3,185	3,703
Greater than 800 | Retail | Education
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	548	1,361
Year two	1,720	1,771
Year three	1,567	840
Year four	694	514
Year five	410	470
Prior to year five	1,068	880
Within the Revolving Period	0	0
Converted to Term	0	0
Total	6,007	5,836
Greater than 800 | Retail | Other retail
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	182	233
Year two	105	214
Year three	93	122
Year four	48	65
Year five	25	30
Prior to year five	27	29
Within the Revolving Period	491	386
Converted to Term	0	0
Total	971	1,079
740-799 | Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	4,305	8,311
Year two	6,084	4,801
Year three	3,557	2,210
Year four	1,539	994
Year five	695	836
Prior to year five	2,422	1,806
Within the Revolving Period	5,324	4,278
Converted to Term	275	280
Total	24,201	23,516
740-799 | Retail | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	2,376	4,015
Year two	2,991	1,876
Year three	1,660	746
Year four	638	246
Year five	257	360
Prior to year five	1,635	1,086
Within the Revolving Period	0	0
Converted to Term	0	0
Total	9,557	8,329
740-799 | Retail | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	2	0
Year two	2	1
Year three	1	4
Year four	4	5
Year five	6	7
Prior to year five	97	122
Within the Revolving Period	4,350	3,514
Converted to Term	274	278
Total	4,736	3,931
740-799 | Retail | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	962	2,418
Year two	1,606	1,051
Year three	649	615
Year four	343	288
Year five	134	156
Prior to year five	56	58
Within the Revolving Period	0	0
Converted to Term	0	0
Total	3,750	4,586
740-799 | Retail | Education
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	735	1,555
Year two	1,351	1,577
Year three	1,126	672
Year four	486	371
Year five	267	275
Prior to year five	609	514
Within the Revolving Period	0	0
Converted to Term	0	0
Total	4,574	4,964
740-799 | Retail | Other retail
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	230	323
Year two	134	296
Year three	121	173
Year four	68	84
Year five	31	38
Prior to year five	25	26
Within the Revolving Period	974	764
Converted to Term	1	2
Total	1,584	1,706
680-739 | Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	2,228	3,842
Year two	2,619	2,114
Year three	1,422	1,193
Year four	790	596
Year five	386	441
Prior to year five	1,311	1,041
Within the Revolving Period	3,289	2,447
Converted to Term	238	248
Total	12,283	11,922
680-739 | Retail | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	769	1,116
Year two	899	572
Year three	502	335
Year four	308	152
Year five	149	172
Prior to year five	851	585
Within the Revolving Period	0	0
Converted to Term	0	0
Total	3,478	2,932
680-739 | Retail | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	1	0
Year two	1	1
Year three	1	7
Year four	6	14
Year five	11	16
Prior to year five	114	134
Within the Revolving Period	2,296	1,738
Converted to Term	234	243
Total	2,664	2,153
680-739 | Retail | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	920	1,968
Year two	1,187	827
Year three	460	500
Year four	254	234
Year five	102	123
Prior to year five	44	48
Within the Revolving Period	0	0
Converted to Term	0	0
Total	2,967	3,700
680-739 | Retail | Education
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	363	512
Year two	423	474
Year three	356	229
Year four	170	140
Year five	103	107
Prior to year five	288	262
Within the Revolving Period	0	0
Converted to Term	0	0
Total	1,703	1,724
680-739 | Retail | Other retail
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	175	246
Year two	109	240
Year three	103	122
Year four	52	56
Year five	21	23
Prior to year five	14	12
Within the Revolving Period	993	709
Converted to Term	4	5
Total	1,471	1,413
620-679 | Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	841	1,339
Year two	896	696
Year three	456	517
Year four	336	296
Year five	214	231
Prior to year five	649	523
Within the Revolving Period	993	662
Converted to Term	147	172
Total	4,532	4,436
620-679 | Retail | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	125	111
Year two	168	130
Year three	135	161
Year four	138	93
Year five	99	107
Prior to year five	422	276
Within the Revolving Period	0	0
Converted to Term	0	0
Total	1,087	878
620-679 | Retail | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0	0
Year two	1	3
Year three	2	11
Year four	9	19
Year five	16	17
Prior to year five	93	112
Within the Revolving Period	558	363
Converted to Term	143	167
Total	822	692
620-679 | Retail | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	554	1,029
Year two	586	378
Year three	205	257
Year four	133	131
Year five	62	72
Prior to year five	28	32
Within the Revolving Period	0	0
Converted to Term	0	0
Total	1,568	1,899
620-679 | Retail | Education
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	54	50
Year two	76	66
Year three	62	45
Year four	38	34
Year five	29	28
Prior to year five	102	99
Within the Revolving Period	0	0
Converted to Term	0	0
Total	361	322
620-679 | Retail | Other retail
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	108	149
Year two	65	119
Year three	52	43
Year four	18	19
Year five	8	7
Prior to year five	4	4
Within the Revolving Period	435	299
Converted to Term	4	5
Total	694	645
Less than 620 | Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	246	225
Year two	423	258
Year three	254	364
Year four	304	310
Year five	236	252
Prior to year five	620	423
Within the Revolving Period	368	191
Converted to Term	178	182
Total	2,629	2,205
Less than 620 | Retail | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	17	24
Year two	68	66
Year three	77	164
Year four	165	162
Year five	147	157
Prior to year five	455	257
Within the Revolving Period	0	0
Converted to Term	0	0
Total	929	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	18	20
Prior to year five	82	87
Within the Revolving Period	178	91
Converted to Term	172	176
Total	464	415
Less than 620 | Retail | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	188	164
Year two	309	142
Year three	130	155
Year four	106	103
Year five	56	62
Prior to year five	31	32
Within the Revolving Period	0	0
Converted to Term	0	0
Total	820	658
Less than 620 | Retail | Education
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	6	5
Year two	16	11
Year three	20	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	115	95
Less than 620 | Retail | Other retail
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	35	32
Year two	30	37
Year three	25	17
Year four	9	10
Year five	4	3
Prior to year five	2	2
Within the Revolving Period	190	100
Converted to Term	6	6
Total	301	207
No FICO available | Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	22	54
Year two	3	13
Year three	5	1
Year four	3	0
Year five	2	0
Prior to year five	59	62
Within the Revolving Period	380	330
Converted to Term	1	1
Total	475	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	2	0
Prior to year five	17	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	2	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	2	3
No FICO available | Retail | Education
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	6	4
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
Prior to year five	42	52
Within the Revolving Period	0	0
Converted to Term	0	0
Total	48	56
No FICO available | Retail | Other retail
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	12	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	380	330
Converted to Term	1	1
Total	$ 397	$ 380