CREDIT QUALITY AND THE ALLOWANCE FOR CREDIT LOSSES - Amortized Cost Basis by Credit Quality Indicator (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2024
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Total	$ 137,635		$ 139,203
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Year one	4	$ 4
Year two	16	16
Year three	13	15
Year four	26	24
Year five	44	69
Prior to year five	86	58
Within the Revolving Period	45	44
Converted to Term	0	1
Total	234	231
Commercial
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	1,952		8,680
Year two	8,080		4,073
Year three	3,729		11,674
Year four	10,974		9,575
Year five	8,802		3,546
Prior to year five	11,116		8,223
Within the Revolving Period	25,630		23,790
Converted to Term	225		215
Total	70,508		69,776
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Year one	0	0
Year two	0	5
Year three	1	1
Year four	10	4
Year five	22	59
Prior to year five	43	30
Within the Revolving Period	9	3
Converted to Term	0	0
Total	85	102
Commercial | Pass
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	1,952		8,665
Year two	8,060		3,830
Year three	3,411		9,942
Year four	9,071		8,335
Year five	7,597		2,814
Prior to year five	8,516		6,265
Within the Revolving Period	24,490		22,757
Converted to Term	77		70
Total	63,174		62,678
Commercial | Special Mention
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	0		3
Year two	5		79
Year three	177		1,009
Year four	1,076		598
Year five	582		223
Prior to year five	572		305
Within the Revolving Period	270		291
Converted to Term	6		6
Total	2,688		2,514
Commercial | Substandard Accrual
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	0		12
Year two	15		86
Year three	134		566
Year four	663		522
Year five	513		414
Prior to year five	1,421		1,128
Within the Revolving Period	785		706
Converted to Term	132		133
Total	3,663		3,567
Commercial | Nonaccrual
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	0		0
Year two	0		78
Year three	7		157
Year four	164		120
Year five	110		95
Prior to year five	607		525
Within the Revolving Period	85		36
Converted to Term	10		6
Total	983		1,017
Commercial | Commercial and industrial
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	1,178		5,956
Year two	5,519		2,679
Year three	2,448		4,567
Year four	4,176		3,490
Year five	3,099		1,087
Prior to year five	3,088		2,422
Within the Revolving Period	24,178		22,265
Converted to Term	95		85
Total	43,781		42,551
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Year one	0	0
Year two	0	5
Year three	1	1
Year four	2	4
Year five	22	0
Prior to year five	0	1
Within the Revolving Period	9	3
Converted to Term	0	0
Total	34	14
Commercial | Commercial and industrial | Pass
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	1,178		5,945
Year two	5,502		2,525
Year three	2,312		4,194
Year four	3,878		2,923
Year five	2,531		895
Prior to year five	2,593		2,066
Within the Revolving Period	23,129		21,323
Converted to Term	73		66
Total	41,196		39,937
Commercial | Commercial and industrial | Special Mention
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	0		2
Year two	5		79
Year three	77		98
Year four	71		236
Year five	227		48
Prior to year five	139		48
Within the Revolving Period	190		211
Converted to Term	0		0
Total	709		722
Commercial | Commercial and industrial | Substandard Accrual
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	0		9
Year two	12		64
Year three	55		207
Year four	144		269
Year five	296		139
Prior to year five	294		253
Within the Revolving Period	776		697
Converted to Term	16		13
Total	1,593		1,651
Commercial | Commercial and industrial | Nonaccrual
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	0		0
Year two	0		11
Year three	4		68
Year four	83		62
Year five	45		5
Prior to year five	62		55
Within the Revolving Period	83		34
Converted to Term	6		6
Total	283		241
Commercial | Commercial real estate
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	774		2,724
Year two	2,561		1,394
Year three	1,281		7,107
Year four	6,798		6,085
Year five	5,703		2,459
Prior to year five	8,028		5,801
Within the Revolving Period	1,452		1,525
Converted to Term	130		130
Total	26,727		27,225
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Year one	0	0
Year two	0	0
Year three	0	0
Year four	8	0
Year five	0	59
Prior to year five	43	29
Within the Revolving Period	0	0
Converted to Term	0	0
Total	51	88
Commercial | Commercial real estate | Pass
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	774		2,720
Year two	2,558		1,305
Year three	1,099		5,748
Year four	5,193		5,412
Year five	5,066		1,919
Prior to year five	5,923		4,199
Within the Revolving Period	1,361		1,434
Converted to Term	4		4
Total	21,978		22,741
Commercial | Commercial real estate | Special Mention
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	0		1
Year two	0		0
Year three	100		911
Year four	1,005		362
Year five	355		175
Prior to year five	433		257
Within the Revolving Period	80		80
Converted to Term	6		6
Total	1,979		1,792
Commercial | Commercial real estate | Substandard Accrual
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	0		3
Year two	3		22
Year three	79		359
Year four	519		253
Year five	217		275
Prior to year five	1,127		875
Within the Revolving Period	9		9
Converted to Term	116		120
Total	2,070		1,916
Commercial | Commercial real estate | Nonaccrual
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	0		0
Year two	0		67
Year three	3		89
Year four	81		58
Year five	65		90
Prior to year five	545		470
Within the Revolving Period	2		2
Converted to Term	4		0
Total	700		776
Retail
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	1,158		4,904
Year two	4,868		4,171
Year three	4,152		8,885
Year four	8,502		13,112
Year five	12,075		7,659
Prior to year five	16,699		11,367
Within the Revolving Period	18,556		18,318
Converted to Term	1,117		1,011
Total	67,127		69,427
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Year one	4	4
Year two	16	11
Year three	12	14
Year four	16	20
Year five	22	10
Prior to year five	43	28
Within the Revolving Period	36	41
Converted to Term	0	1
Total	149	129
Retail | Residential mortgages
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	882		3,459
Year two	3,425		2,554
Year three	2,690		5,621
Year four	5,696		8,318
Year five	8,348		4,833
Prior to year five	12,073		7,941
Within the Revolving Period	0		0
Converted to Term	0		0
Total	33,114		32,726
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Year one	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
Prior to year five	1	2
Within the Revolving Period	0	0
Converted to Term	0	0
Total	1	2
Retail | Home equity
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	0		1
Year two	1		3
Year three	4		15
Year four	8		12
Year five	11		6
Prior to year five	205		336
Within the Revolving Period	15,510		15,115
Converted to Term	1,114		1,007
Total	16,853		16,495
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Year one	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
Prior to year five	1	1
Within the Revolving Period	4	2
Converted to Term	0	1
Total	5	4
Retail | Automobile
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	0		0
Year two	0		346
Year three	327		1,534
Year four	1,363		2,041
Year five	1,746		592
Prior to year five	608		231
Within the Revolving Period	0		0
Converted to Term	0		0
Total	4,044		4,744
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Year one	0	0
Year two	0	2
Year three	2	9
Year four	7	11
Year five	7	3
Prior to year five	4	3
Within the Revolving Period	0	0
Converted to Term	0	0
Total	20	28
Retail | Education
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	165		664
Year two	800		942
Year three	864		1,533
Year four	1,269		2,668
Year five	1,915		2,180
Prior to year five	3,766		2,825
Within the Revolving Period	0		0
Converted to Term	0		0
Total	8,779		10,812
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Year one	0	0
Year two	1	0
Year three	2	1
Year four	5	6
Year five	13	7
Prior to year five	35	18
Within the Revolving Period	0	0
Converted to Term	0	0
Total	56	32
Retail | Other retail
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	111		780
Year two	642		326
Year three	267		182
Year four	166		73
Year five	55		48
Prior to year five	47		34
Within the Revolving Period	3,046		3,203
Converted to Term	3		4
Total	4,337		4,650
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Year one	4	4
Year two	15	9
Year three	8	4
Year four	4	3
Year five	2	0
Prior to year five	2	4
Within the Revolving Period	32	39
Converted to Term	0	0
Total	67	$ 63
Greater than 800 | Retail
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	312		1,644
Year two	2,006		1,805
Year three	1,834		4,375
Year four	4,266		7,310
Year five	6,844		4,370
Prior to year five	9,047		5,488
Within the Revolving Period	6,243		6,146
Converted to Term	193		200
Total	30,745		31,338
Greater than 800 | Retail | Residential mortgages
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	232		1,230
Year two	1,568		1,302
Year three	1,369		3,299
Year four	3,343		5,109
Year five	5,149		2,919
Prior to year five	6,701		3,869
Within the Revolving Period	0		0
Converted to Term	0		0
Total	18,362		17,728
Greater than 800 | Retail | Home equity
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	0		1
Year two	1		0
Year three	0		3
Year four	3		4
Year five	3		1
Prior to year five	75		76
Within the Revolving Period	5,770		5,634
Converted to Term	193		200
Total	6,045		5,919
Greater than 800 | Retail | Automobile
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	0		0
Year two	0		65
Year three	63		380
Year four	343		665
Year five	575		183
Prior to year five	177		58
Within the Revolving Period	0		0
Converted to Term	0		0
Total	1,158		1,351
Greater than 800 | Retail | Education
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	52		227
Year two	282		373
Year three	347		657
Year four	543		1,517
Year five	1,104		1,256
Prior to year five	2,081		1,475
Within the Revolving Period	0		0
Converted to Term	0		0
Total	4,409		5,505
Greater than 800 | Retail | Other retail
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	28		186
Year two	155		65
Year three	55		36
Year four	34		15
Year five	13		11
Prior to year five	13		10
Within the Revolving Period	473		512
Converted to Term	0		0
Total	771		835
740-799 | Retail
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	634		2,306
Year two	1,940		1,420
Year three	1,301		2,616
Year four	2,419		3,618
Year five	3,197		2,165
Prior to year five	4,333		2,871
Within the Revolving Period	6,218		6,170
Converted to Term	224		225
Total	20,266		21,391
740-799 | Retail | Residential mortgages
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	520		1,757
Year two	1,410		873
Year three	817		1,568
Year four	1,537		2,213
Year five	2,142		1,338
Prior to year five	3,031		1,923
Within the Revolving Period	0		0
Converted to Term	0		0
Total	9,457		9,672
740-799 | Retail | Home equity
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	0		0
Year two	0		0
Year three	0		1
Year four	1		2
Year five	3		1
Prior to year five	52		65
Within the Revolving Period	5,382		5,275
Converted to Term	224		224
Total	5,662		5,568
740-799 | Retail | Automobile
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	0		0
Year two	0		92
Year three	87		430
Year four	376		581
Year five	482		176
Prior to year five	172		61
Within the Revolving Period	0		0
Converted to Term	0		0
Total	1,117		1,340
740-799 | Retail | Education
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	75		290
Year two	321		359
Year three	320		571
Year four	463		804
Year five	556		637
Prior to year five	1,064		811
Within the Revolving Period	0		0
Converted to Term	0		0
Total	2,799		3,472
740-799 | Retail | Other retail
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	39		259
Year two	209		96
Year three	77		46
Year four	42		18
Year five	14		13
Prior to year five	14		11
Within the Revolving Period	836		895
Converted to Term	0		1
Total	1,231		1,339
680-739 | Retail
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	176		736
Year two	689		609
Year three	585		1,159
Year four	1,065		1,358
Year five	1,234		723
Prior to year five	1,758		1,403
Within the Revolving Period	3,872		3,840
Converted to Term	207		184
Total	9,586		10,012
680-739 | Retail | Residential mortgages
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	119		425
Year two	382		281
Year three	295		552
Year four	546		697
Year five	713		385
Prior to year five	1,193		938
Within the Revolving Period	0		0
Converted to Term	0		0
Total	3,248		3,278
680-739 | Retail | Home equity
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	0		0
Year two	0		0
Year three	0		1
Year four	1		0
Year five	1		1
Prior to year five	43		76
Within the Revolving Period	3,064		2,995
Converted to Term	206		183
Total	3,315		3,256
680-739 | Retail | Automobile
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	0		0
Year two	0		91
Year three	82		338
Year four	289		385
Year five	322		115
Prior to year five	114		45
Within the Revolving Period	0		0
Converted to Term	0		0
Total	807		974
680-739 | Retail | Education
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	29		110
Year two	145		150
Year three	139		229
Year four	193		261
Year five	186		211
Prior to year five	397		337
Within the Revolving Period	0		0
Converted to Term	0		0
Total	1,089		1,298
680-739 | Retail | Other retail
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	28		201
Year two	162		87
Year three	69		39
Year four	36		15
Year five	12		11
Prior to year five	11		7
Within the Revolving Period	808		845
Converted to Term	1		1
Total	1,127		1,206
620-679 | Retail
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	27		155
Year two	167		208
Year three	204		401
Year four	388		416
Year five	401		216
Prior to year five	705		697
Within the Revolving Period	1,106		1,087
Converted to Term	179		142
Total	3,177		3,322
620-679 | Retail | Residential mortgages
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	11		31
Year two	46		61
Year three	76		126
Year four	149		151
Year five	180		101
Prior to year five	494		494
Within the Revolving Period	0		0
Converted to Term	0		0
Total	956		964
620-679 | Retail | Home equity
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	0		0
Year two	0		1
Year three	1		4
Year four	1		3
Year five	1		2
Prior to year five	19		60
Within the Revolving Period	788		752
Converted to Term	178		141
Total	988		963
620-679 | Retail | Automobile
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	0		0
Year two	0		51
Year three	46		189
Year four	166		194
Year five	167		56
Prior to year five	64		29
Within the Revolving Period	0		0
Converted to Term	0		0
Total	443		519
620-679 | Retail | Education
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	4		27
Year two	42		48
Year three	43		55
Year four	48		58
Year five	45		51
Prior to year five	123		111
Within the Revolving Period	0		0
Converted to Term	0		0
Total	305		350
620-679 | Retail | Other retail
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	12		97
Year two	79		47
Year three	38		27
Year four	24		10
Year five	8		6
Prior to year five	5		3
Within the Revolving Period	318		335
Converted to Term	1		1
Total	485		526
Less than 620 | Retail
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	3		52
Year two	62		129
Year three	228		334
Year four	361		409
Year five	398		184
Prior to year five	816		863
Within the Revolving Period	737		693
Converted to Term	314		260
Total	2,919		2,924
Less than 620 | Retail | Residential mortgages
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	0		15
Year two	18		37
Year three	133		76
Year four	118		147
Year five	163		89
Prior to year five	643		703
Within the Revolving Period	0		0
Converted to Term	0		0
Total	1,075		1,067
Less than 620 | Retail | Home equity
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	0		0
Year two	0		2
Year three	3		6
Year four	2		3
Year five	3		1
Prior to year five	16		59
Within the Revolving Period	501		459
Converted to Term	313		259
Total	838		789
Less than 620 | Retail | Automobile
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	0		0
Year two	0		47
Year three	49		197
Year four	189		216
Year five	200		62
Prior to year five	81		38
Within the Revolving Period	0		0
Converted to Term	0		0
Total	519		560
Less than 620 | Retail | Education
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	1		5
Year two	9		12
Year three	15		21
Year four	22		28
Year five	24		25
Prior to year five	72		60
Within the Revolving Period	0		0
Converted to Term	0		0
Total	143		151
Less than 620 | Retail | Other retail
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	2		32
Year two	35		31
Year three	28		34
Year four	30		15
Year five	8		7
Prior to year five	4		3
Within the Revolving Period	236		234
Converted to Term	1		1
Total	344		357
No FICO available | Retail
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	6		11
Year two	4		0
Year three	0		0
Year four	3		1
Year five	1		1
Prior to year five	40		45
Within the Revolving Period	380		382
Converted to Term	0		0
Total	434		440
No FICO available | Retail | Residential mortgages
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	0		1
Year two	1		0
Year three	0		0
Year four	3		1
Year five	1		1
Prior to year five	11		14
Within the Revolving Period	0		0
Converted to Term	0		0
Total	16		17
No FICO available | Retail | Home equity
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
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		0
Within the Revolving Period	5		0
Converted to Term	0		0
Total	5		0
No FICO available | Retail | Automobile
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
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		0
Within the Revolving Period	0		0
Converted to Term	0		0
Total	0		0
No FICO available | Retail | Education
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	4		5
Year two	1		0
Year three	0		0
Year four	0		0
Year five	0		0
Prior to year five	29		31
Within the Revolving Period	0		0
Converted to Term	0		0
Total	34		36
No FICO available | Retail | Other retail
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one	2		5
Year two	2		0
Year three	0		0
Year four	0		0
Year five	0		0
Prior to year five	0		0
Within the Revolving Period	375		382
Converted to Term	0		0
Total	$ 379		$ 387