LOANS - Corporate Loans Credit Quality Indicators (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 688,922	$ 689,362
Loans at fair value	8,106	7,594
Unallocated portfolio layer cumulative basis adjustments	299	93
Corporate loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	79,068	90,737
One year prior to current fiscal year	28,974	27,788
Two years prior to current fiscal year	21,340	15,899
Three years prior to current fiscal year	11,956	8,869
Four years prior to current fiscal year	6,005	7,313
Prior	20,039	20,008
Revolving line of credit arrangements	124,520	122,177
Loans, net of unearned income	299,771	300,165
Loans at fair value	7,804	7,281
Loans net of unearned income, before adjustments	299,706	300,072
Unallocated portfolio layer cumulative basis adjustments	65	93
Corporate loans | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	154,111	151,451
Corporate loans | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	64,388	65,060
Corporate loans | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	26,252	24,938
Corporate loans | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	46,877	51,067
Corporate loans | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	55,074	67,094
One year prior to current fiscal year	21,585	20,308
Two years prior to current fiscal year	14,731	11,142
Three years prior to current fiscal year	7,833	6,276
Four years prior to current fiscal year	4,730	5,211
Prior	15,190	15,638
Revolving line of credit arrangements	100,665	101,072
Loans, net of unearned income	219,808	226,741
Corporate loans | Investment grade | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	38,306	47,811
One year prior to current fiscal year	11,198	7,738
Two years prior to current fiscal year	5,627	3,641
Three years prior to current fiscal year	3,187	2,279
Four years prior to current fiscal year	1,636	2,604
Prior	6,447	6,907
Revolving line of credit arrangements	34,525	34,956
Loans, net of unearned income	100,926	105,936
Corporate loans | Investment grade | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	9,203	11,002
One year prior to current fiscal year	3,136	2,356
Two years prior to current fiscal year	1,371	2,834
Three years prior to current fiscal year	795	424
Four years prior to current fiscal year	282	557
Prior	1,736	1,847
Revolving line of credit arrangements	40,053	36,715
Loans, net of unearned income	56,576	55,735
Corporate loans | Investment grade | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	3,687	3,628
One year prior to current fiscal year	4,177	4,433
Two years prior to current fiscal year	3,826	3,595
Three years prior to current fiscal year	3,030	2,544
Four years prior to current fiscal year	2,075	1,238
Prior	1,824	1,582
Revolving line of credit arrangements	235	66
Loans, net of unearned income	18,854	17,086
Corporate loans | Investment grade | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	3,878	4,653
One year prior to current fiscal year	3,074	5,781
Two years prior to current fiscal year	3,907	1,072
Three years prior to current fiscal year	821	1,029
Four years prior to current fiscal year	737	812
Prior	5,183	5,302
Revolving line of credit arrangements	25,852	29,335
Loans, net of unearned income	43,452	47,984
Corporate loans | Non-investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	23,994	23,643
One year prior to current fiscal year	7,389	7,480
Two years prior to current fiscal year	6,609	4,757
Three years prior to current fiscal year	4,123	2,593
Four years prior to current fiscal year	1,275	2,102
Prior	4,849	4,370
Revolving line of credit arrangements	23,855	21,105
Loans, net of unearned income	72,094	66,050
Corporate loans | Non-investment grade, accrual | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	19,506	17,570
One year prior to current fiscal year	5,242	4,785
Two years prior to current fiscal year	3,929	1,914
Three years prior to current fiscal year	1,939	1,359
Four years prior to current fiscal year	284	732
Prior	2,656	2,526
Revolving line of credit arrangements	19,275	15,912
Loans, net of unearned income	52,831	44,798
Corporate loans | Non-investment grade, accrual | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	3,331	4,207
One year prior to current fiscal year	679	748
Two years prior to current fiscal year	437	1,084
Three years prior to current fiscal year	456	56
Four years prior to current fiscal year	1	194
Prior	323	260
Revolving line of credit arrangements	2,557	2,725
Loans, net of unearned income	7,784	9,274
Corporate loans | Non-investment grade, accrual | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	473	1,034
One year prior to current fiscal year	877	1,234
Two years prior to current fiscal year	1,670	1,378
Three years prior to current fiscal year	1,384	947
Four years prior to current fiscal year	726	755
Prior	1,322	1,016
Revolving line of credit arrangements	471	620
Loans, net of unearned income	6,923	6,984
Corporate loans | Non-investment grade, accrual | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	642	653
One year prior to current fiscal year	540	434
Two years prior to current fiscal year	374	248
Three years prior to current fiscal year	274	158
Four years prior to current fiscal year	220	211
Prior	251	155
Revolving line of credit arrangements	1,311	1,253
Loans, net of unearned income	3,612	3,112
Corporate loans | Non-investment grade, non-accrual | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	32	53
One year prior to current fiscal year	40	46
Two years prior to current fiscal year	43	84
Three years prior to current fiscal year	28	35
Four years prior to current fiscal year	15	45
Prior	39	93
Revolving line of credit arrangements	156	361
Loans, net of unearned income	353	717
Corporate loans | Non-investment grade, non-accrual | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	3	0
One year prior to current fiscal year	0	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	24	51
Loans, net of unearned income	27	51
Corporate loans | Non-investment grade, non-accrual | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	1	118
One year prior to current fiscal year	3	233
Two years prior to current fiscal year	156	8
Three years prior to current fiscal year	7	38
Four years prior to current fiscal year	29	110
Prior	244	308
Revolving line of credit arrangements	36	53
Loans, net of unearned income	476	868
Corporate loans | Non-investment grade, non-accrual | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	6	8
One year prior to current fiscal year	8	0
Two years prior to current fiscal year	0	41
Three years prior to current fiscal year	35	0
Four years prior to current fiscal year	0	55
Prior	14	12
Revolving line of credit arrangements	25	130
Loans, net of unearned income	$ 88	$ 246