LOANS - Corporate Loans Credit Quality Indicators (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	$ 659,669	$ 667,767
Loans at fair value	5,732	6,082
Lease financing
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	400	500
Corporate
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	309,341	291,233
Total non-accrual	1,866	1,553
Loans at fair value	5,722	6,070
Corporate | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	163,361	147,004
Total non-accrual	1,519	1,263
Corporate | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	75,242	71,767
Total non-accrual	52	2
Corporate | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	22,190	20,291
Total non-accrual	119	136
Corporate | Lease financing
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	426	455
Total non-accrual	15	14
Corporate | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	42,400	45,646
Total non-accrual	161	138
Corporate | Corporate loans, net of unearned income
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	66,698	90,549
One year prior to current fiscal year	38,494	17,944
Two years prior to current fiscal year	16,512	15,094
Three years prior to current fiscal year	13,954	13,278
Four years prior to current fiscal year	12,136	7,071
Prior	27,474	21,190
Revolving line of credit arrangements	128,351	120,037
Total loans, net of unearned income	309,341	291,233
Loans at fair value	5,722	6,070
Corporate | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	50,745	66,744
One year prior to current fiscal year	26,176	13,966
Two years prior to current fiscal year	12,476	10,317
Three years prior to current fiscal year	9,728	9,599
Four years prior to current fiscal year	8,770	4,872
Prior	19,763	15,635
Revolving line of credit arrangements	99,362	93,086
Total loans, net of unearned income	227,020	214,219
Corporate | Investment grade | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	36,059	42,422
One year prior to current fiscal year	13,020	5,529
Two years prior to current fiscal year	4,742	4,642
Three years prior to current fiscal year	4,219	3,757
Four years prior to current fiscal year	3,513	2,911
Prior	10,875	8,392
Revolving line of credit arrangements	36,661	30,588
Total loans, net of unearned income	109,089	98,241
Corporate | Investment grade | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	9,481	12,862
One year prior to current fiscal year	6,754	1,678
Two years prior to current fiscal year	1,663	1,183
Three years prior to current fiscal year	1,107	1,038
Four years prior to current fiscal year	931	419
Prior	1,923	1,354
Revolving line of credit arrangements	42,885	43,630
Total loans, net of unearned income	64,744	62,164
Corporate | Investment grade | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	1,862	2,423
One year prior to current fiscal year	3,077	3,660
Two years prior to current fiscal year	3,720	3,332
Three years prior to current fiscal year	3,409	2,015
Four years prior to current fiscal year	1,824	1,212
Prior	2,477	1,288
Revolving line of credit arrangements	117	141
Total loans, net of unearned income	16,486	14,071
Corporate | Investment grade | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	3,343	9,037
One year prior to current fiscal year	3,325	3,099
Two years prior to current fiscal year	2,351	1,160
Three years prior to current fiscal year	993	2,789
Four years prior to current fiscal year	2,502	330
Prior	4,488	4,601
Revolving line of credit arrangements	19,699	18,727
Total loans, net of unearned income	36,701	39,743
Corporate | Non-investment grade, accrual | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	11,346	16,783
One year prior to current fiscal year	8,485	2,281
Two years prior to current fiscal year	2,448	2,343
Three years prior to current fiscal year	2,145	2,024
Four years prior to current fiscal year	1,790	1,412
Prior	5,253	3,981
Revolving line of credit arrangements	21,286	18,676
Total loans, net of unearned income	52,753	47,500
Corporate | Non-investment grade, accrual | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	3,337	4,325
One year prior to current fiscal year	1,760	347
Two years prior to current fiscal year	346	567
Three years prior to current fiscal year	553	101
Four years prior to current fiscal year	56	71
Prior	750	511
Revolving line of credit arrangements	3,644	3,679
Total loans, net of unearned income	10,446	9,601
Corporate | Non-investment grade, accrual | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	141	1,275
One year prior to current fiscal year	922	869
Two years prior to current fiscal year	741	1,228
Three years prior to current fiscal year	1,005	1,018
Four years prior to current fiscal year	1,141	493
Prior	1,017	586
Revolving line of credit arrangements	618	615
Total loans, net of unearned income	5,585	6,084
Corporate | Non-investment grade, accrual | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	910	1,339
One year prior to current fiscal year	949	349
Two years prior to current fiscal year	398	554
Three years prior to current fiscal year	390	364
Four years prior to current fiscal year	201	119
Prior	358	245
Revolving line of credit arrangements	2,743	3,236
Total loans, net of unearned income	5,949	6,206
Corporate | Non-investment grade, non-accrual | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	143	53
One year prior to current fiscal year	148	119
Two years prior to current fiscal year	99	64
Three years prior to current fiscal year	122	104
Four years prior to current fiscal year	112	94
Prior	245	117
Revolving line of credit arrangements	650	712
Total non-accrual	1,519	1,263
Corporate | Non-investment grade, non-accrual | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
One year prior to current fiscal year	50	0
Two years prior to current fiscal year	0	0
Three years prior to current fiscal year	0	0
Four years prior to current fiscal year	0	0
Prior	0	0
Revolving line of credit arrangements	2	2
Total non-accrual	52	2
Corporate | Non-investment grade, non-accrual | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	10	11
One year prior to current fiscal year	0	8
Two years prior to current fiscal year	1	2
Three years prior to current fiscal year	0	49
Four years prior to current fiscal year	42	10
Prior	25	25
Revolving line of credit arrangements	41	31
Total non-accrual	119	136
Corporate | Non-investment grade, non-accrual | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	66	19
One year prior to current fiscal year	4	5
Two years prior to current fiscal year	3	19
Three years prior to current fiscal year	11	19
Four years prior to current fiscal year	24	0
Prior	63	90
Revolving line of credit arrangements	5	0
Total non-accrual	176	152
Corporate | Non-investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	15,953	23,805
One year prior to current fiscal year	12,318	3,978
Two years prior to current fiscal year	4,036	4,777
Three years prior to current fiscal year	4,226	3,679
Four years prior to current fiscal year	3,366	2,199
Prior	7,711	5,555
Revolving line of credit arrangements	28,989	26,951
Total loans, net of unearned income	$ 76,599	$ 70,944