LOANS - Corporate Loans Credit Quality Indicators (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	$ 666,348	$ 657,221
Loans at fair value	7,411	5,360
Cumulative basis adjustments	(171)
Corporate loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	288,634	289,154
Total non-accrual	1,975	1,122
Loans at fair value	7,189	5,123
Cumulative basis adjustments	(171)	0
Corporate loans | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income		147,803
Total non-accrual	903	860
Corporate loans | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income		64,907
Total non-accrual	87	152
Corporate loans | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income		21,949
Total non-accrual	821	33
Corporate loans | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income		49,018
Total non-accrual	164	67
Corporate loans | Corporate loans, net of unearned income(7)
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	76,634	88,444
One year prior to current fiscal year	30,777	21,137
Two years prior to current fiscal year	17,782	13,019
Three years prior to current fiscal year	9,569	10,492
Four years prior to current fiscal year	8,224	8,051
Prior	20,963	18,854
Revolving line of credit arrangements	117,667	124,034
Total loans, net of unearned income	288,805	289,154
Loans at fair value	7,189	5,123
Corporate loans | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	56,132	64,574
One year prior to current fiscal year	22,514	15,924
Two years prior to current fiscal year	13,135	9,904
Three years prior to current fiscal year	6,996	7,642
Four years prior to current fiscal year	6,017	6,196
Prior	16,116	13,913
Revolving line of credit arrangements	97,193	102,777
Total loans, net of unearned income	218,103	220,930
Corporate loans | Investment grade | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	42,312	40,639
One year prior to current fiscal year	7,844	6,124
Two years prior to current fiscal year	4,809	3,620
Three years prior to current fiscal year	2,441	3,458
Four years prior to current fiscal year	2,751	2,617
Prior	7,538	7,048
Revolving line of credit arrangements	36,301	38,358
Total loans, net of unearned income	103,996	101,864
Corporate loans | Investment grade | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	9,518	11,850
One year prior to current fiscal year	4,050	3,877
Two years prior to current fiscal year	3,048	835
Three years prior to current fiscal year	520	922
Four years prior to current fiscal year	603	333
Prior	1,978	1,327
Revolving line of credit arrangements	33,069	37,462
Total loans, net of unearned income	52,786	56,606
Corporate loans | Investment grade | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	2,075	4,436
One year prior to current fiscal year	4,881	3,236
Two years prior to current fiscal year	3,874	4,010
Three years prior to current fiscal year	3,026	2,619
Four years prior to current fiscal year	1,725	1,127
Prior	1,903	1,706
Revolving line of credit arrangements	141	152
Total loans, net of unearned income	17,625	17,286
Corporate loans | Investment grade | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	2,227	7,649
One year prior to current fiscal year	5,739	2,687
Two years prior to current fiscal year	1,404	1,439
Three years prior to current fiscal year	1,009	643
Four years prior to current fiscal year	938	2,119
Prior	4,697	3,832
Revolving line of credit arrangements	27,682	26,805
Total loans, net of unearned income	43,696	45,174
Corporate loans | Non-investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	20,502	23,870
One year prior to current fiscal year	8,263	5,213
Two years prior to current fiscal year	4,647	3,115
Three years prior to current fiscal year	2,573	2,850
Four years prior to current fiscal year	2,207	1,855
Prior	4,847	4,941
Revolving line of credit arrangements	20,474	21,257
Total loans, net of unearned income	63,513	63,101
Corporate loans | Non-investment grade, accrual | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	16,057	17,278
One year prior to current fiscal year	5,183	3,139
Two years prior to current fiscal year	2,328	1,973
Three years prior to current fiscal year	1,650	1,331
Four years prior to current fiscal year	920	965
Prior	2,967	3,546
Revolving line of credit arrangements	16,391	16,848
Total loans, net of unearned income	45,496	45,080
Corporate loans | Non-investment grade, accrual | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	3,172	4,708
One year prior to current fiscal year	1,115	630
Two years prior to current fiscal year	842	197
Three years prior to current fiscal year	16	254
Four years prior to current fiscal year	175	47
Prior	205	240
Revolving line of credit arrangements	1,748	2,073
Total loans, net of unearned income	7,273	8,149
Corporate loans | Non-investment grade, accrual | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	658	582
One year prior to current fiscal year	776	835
Two years prior to current fiscal year	946	429
Three years prior to current fiscal year	677	729
Four years prior to current fiscal year	653	783
Prior	1,103	801
Revolving line of credit arrangements	602	472
Total loans, net of unearned income	5,415	4,631
Corporate loans | Non-investment grade, accrual | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	513	1,244
One year prior to current fiscal year	786	559
Two years prior to current fiscal year	376	391
Three years prior to current fiscal year	202	413
Four years prior to current fiscal year	215	1
Prior	132	219
Revolving line of credit arrangements	1,130	1,292
Total loans, net of unearned income	3,354	4,119
Corporate loans | Non-investment grade, non-accrual | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	80	1
One year prior to current fiscal year	71	12
Two years prior to current fiscal year	74	99
Three years prior to current fiscal year	0	115
Four years prior to current fiscal year	45	49
Prior	178	105
Revolving line of credit arrangements	455	479
Total non-accrual	903	860
Corporate loans | Non-investment grade, non-accrual | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	7	41
One year prior to current fiscal year	3	34
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	0	0
Revolving line of credit arrangements	49	77
Total non-accrual	87	152
Corporate loans | Non-investment grade, non-accrual | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	3	10
One year prior to current fiscal year	329	4
Two years prior to current fiscal year	12	0
Three years prior to current fiscal year	28	0
Four years prior to current fiscal year	137	0
Prior	260	19
Revolving line of credit arrangements	52	0
Total non-accrual	821	33
Corporate loans | Non-investment grade, non-accrual | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	12	6
One year prior to current fiscal year	0	0
Two years prior to current fiscal year	41	26
Three years prior to current fiscal year	0	8
Four years prior to current fiscal year	62	10
Prior	2	11
Revolving line of credit arrangements	47	16
Total non-accrual	$ 164	$ 77