LOANS - Corporate Loans Credit Quality Indicators (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 651,995	$ 657,221
Loans at fair value	5,134	5,360
Corporate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	288,299	289,154
Total non-accrual	1,213	1,122
Loans at fair value	4,896	5,123
Corporate | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	150,330	147,803
Total non-accrual	909	860
Corporate | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	60,434	64,907
Total non-accrual	158	152
Corporate | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	23,478	21,949
Total non-accrual	89	33
Corporate | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	48,813	49,018
Total non-accrual	57	67
Corporate | Corporate loans, net of unearned income
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	53,036	88,444
One year prior to current fiscal year	42,959	21,137
Two years prior to current fiscal year	20,029	13,019
Three years prior to current fiscal year	11,589	10,492
Four years prior to current fiscal year	9,679	8,051
Prior	24,742	18,854
Revolving line of credit arrangements	121,369	124,034
Loans, net of unearned income	288,299	289,154
Loans at fair value	4,896	5,123
Corporate | Corporate loans, net of unearned income | Revision of Prior Period, Adjustment
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year		(24,900)
One year prior to current fiscal year		2,000
Two years prior to current fiscal year		3,200
Three years prior to current fiscal year		4,600
Four years prior to current fiscal year		4,100
Prior		11,000
Corporate | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	38,680	64,574
One year prior to current fiscal year	30,706	15,924
Two years prior to current fiscal year	15,007	9,904
Three years prior to current fiscal year	8,389	7,642
Four years prior to current fiscal year	6,938	6,196
Prior	18,313	13,913
Revolving line of credit arrangements	100,006	102,777
Loans, net of unearned income	218,039	220,930
Corporate | Investment grade | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	30,374	40,639
One year prior to current fiscal year	12,281	6,124
Two years prior to current fiscal year	5,870	3,620
Three years prior to current fiscal year	2,895	3,458
Four years prior to current fiscal year	3,241	2,617
Prior	8,888	7,048
Revolving line of credit arrangements	39,492	38,358
Loans, net of unearned income	103,041	101,864
Corporate | Investment grade | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	5,658	11,850
One year prior to current fiscal year	6,899	3,877
Two years prior to current fiscal year	3,872	835
Three years prior to current fiscal year	602	922
Four years prior to current fiscal year	717	333
Prior	1,766	1,327
Revolving line of credit arrangements	32,909	37,462
Loans, net of unearned income	52,423	56,606
Corporate | Investment grade | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	906	4,436
One year prior to current fiscal year	5,081	3,236
Two years prior to current fiscal year	3,347	4,010
Three years prior to current fiscal year	3,669	2,619
Four years prior to current fiscal year	2,112	1,127
Prior	2,835	1,706
Revolving line of credit arrangements	120	152
Loans, net of unearned income	18,070	17,286
Corporate | Investment grade | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	1,742	7,649
One year prior to current fiscal year	6,445	2,687
Two years prior to current fiscal year	1,918	1,439
Three years prior to current fiscal year	1,223	643
Four years prior to current fiscal year	868	2,119
Prior	4,824	3,832
Revolving line of credit arrangements	27,485	26,805
Loans, net of unearned income	44,505	45,174
Corporate | Non-investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	14,356	23,870
One year prior to current fiscal year	12,253	5,213
Two years prior to current fiscal year	5,022	3,115
Three years prior to current fiscal year	3,200	2,850
Four years prior to current fiscal year	2,741	1,855
Prior	6,429	4,941
Revolving line of credit arrangements	21,363	21,257
Loans, net of unearned income	65,364	63,101
Corporate | Non-investment grade, accrual | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	10,901	17,278
One year prior to current fiscal year	8,199	3,139
Two years prior to current fiscal year	2,848	1,973
Three years prior to current fiscal year	1,868	1,331
Four years prior to current fiscal year	1,111	965
Prior	4,190	3,546
Revolving line of credit arrangements	17,017	16,848
Loans, net of unearned income	46,134	45,080
Corporate | Non-investment grade, accrual | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	2,347	4,708
One year prior to current fiscal year	2,396	630
Two years prior to current fiscal year	717	197
Three years prior to current fiscal year	178	254
Four years prior to current fiscal year	362	47
Prior	233	240
Revolving line of credit arrangements	1,870	2,073
Loans, net of unearned income	8,103	8,149
Corporate | Non-investment grade, accrual | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	597	582
One year prior to current fiscal year	551	835
Two years prior to current fiscal year	860	429
Three years prior to current fiscal year	592	729
Four years prior to current fiscal year	722	783
Prior	1,577	801
Revolving line of credit arrangements	418	472
Loans, net of unearned income	5,317	4,631
Corporate | Non-investment grade, accrual | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	505	1,244
One year prior to current fiscal year	1,049	559
Two years prior to current fiscal year	502	391
Three years prior to current fiscal year	509	413
Four years prior to current fiscal year	435	1
Prior	222	219
Revolving line of credit arrangements	1,375	1,292
Loans, net of unearned income	4,597	4,119
Corporate | Non-investment grade, non-accrual | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	1
One year prior to current fiscal year	7	12
Two years prior to current fiscal year	32	99
Three years prior to current fiscal year	46	115
Four years prior to current fiscal year	111	49
Prior	164	105
Revolving line of credit arrangements	549	479
Total non-accrual	909	860
Corporate | Non-investment grade, non-accrual | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	41
One year prior to current fiscal year	41	34
Two years prior to current fiscal year	35	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	82	77
Total non-accrual	158	152
Corporate | Non-investment grade, non-accrual | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	10
One year prior to current fiscal year	0	4
Two years prior to current fiscal year	28	0
Three years prior to current fiscal year	0	0
Four years prior to current fiscal year	0	0
Prior	40	19
Revolving line of credit arrangements	21	0
Total non-accrual	89	33
Corporate | Non-investment grade, non-accrual | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	6	6
One year prior to current fiscal year	10	0
Two years prior to current fiscal year	0	26
Three years prior to current fiscal year	7	8
Four years prior to current fiscal year	0	10
Prior	3	11
Revolving line of credit arrangements	31	16
Total non-accrual	$ 57	$ 77