LOANS - Corporate Loans Credit Quality Indicators (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 687,722	$ 689,362
Loans at fair value	8,526	7,594
Unallocated portfolio layer cumulative basis adjustments	(213)	93
Corporate loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	70,122	90,737
One year prior to current fiscal year	31,963	27,788
Two years prior to current fiscal year	23,055	15,899
Three years prior to current fiscal year	14,505	8,869
Four years prior to current fiscal year	6,884	7,313
Prior	22,093	20,008
Revolving line of credit arrangements	124,774	122,177
Loans, net of unearned income	301,605	300,165
Loans at fair value	8,232	7,281
Loans net of unearned income, before adjustments	301,628	300,072
Unallocated portfolio layer cumulative basis adjustments	(23)	93
Corporate loans | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	154,266	151,451
Corporate loans | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	66,736	65,060
Corporate loans | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	25,199	24,938
Corporate loans | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	46,928	51,067
Corporate loans | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	49,487	67,094
One year prior to current fiscal year	23,767	20,308
Two years prior to current fiscal year	16,416	11,142
Three years prior to current fiscal year	9,954	6,276
Four years prior to current fiscal year	5,314	5,211
Prior	17,103	15,638
Revolving line of credit arrangements	101,901	101,072
Loans, net of unearned income	223,942	226,741
Corporate loans | Investment grade | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	36,934	47,811
One year prior to current fiscal year	12,455	7,738
Two years prior to current fiscal year	6,376	3,641
Three years prior to current fiscal year	3,539	2,279
Four years prior to current fiscal year	1,920	2,604
Prior	7,363	6,907
Revolving line of credit arrangements	35,179	34,956
Loans, net of unearned income	103,766	105,936
Corporate loans | Investment grade | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	8,774	11,002
One year prior to current fiscal year	4,555	2,356
Two years prior to current fiscal year	1,744	2,834
Three years prior to current fiscal year	2,022	424
Four years prior to current fiscal year	360	557
Prior	2,190	1,847
Revolving line of credit arrangements	39,235	36,715
Loans, net of unearned income	58,880	55,735
Corporate loans | Investment grade | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	1,436	3,628
One year prior to current fiscal year	3,636	4,433
Two years prior to current fiscal year	3,917	3,595
Three years prior to current fiscal year	3,380	2,544
Four years prior to current fiscal year	2,212	1,238
Prior	2,515	1,582
Revolving line of credit arrangements	268	66
Loans, net of unearned income	17,364	17,086
Corporate loans | Investment grade | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	2,343	4,653
One year prior to current fiscal year	3,121	5,781
Two years prior to current fiscal year	4,379	1,072
Three years prior to current fiscal year	1,013	1,029
Four years prior to current fiscal year	822	812
Prior	5,035	5,302
Revolving line of credit arrangements	27,219	29,335
Loans, net of unearned income	43,932	47,984
Corporate loans | Non-investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	20,635	23,643
One year prior to current fiscal year	8,196	7,480
Two years prior to current fiscal year	6,639	4,757
Three years prior to current fiscal year	4,551	2,593
Four years prior to current fiscal year	1,570	2,102
Prior	4,990	4,370
Revolving line of credit arrangements	22,873	21,105
Loans, net of unearned income	69,454	66,050
Corporate loans | Non-investment grade, accrual | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	17,439	17,570
One year prior to current fiscal year	5,666	4,785
Two years prior to current fiscal year	3,874	1,914
Three years prior to current fiscal year	1,962	1,359
Four years prior to current fiscal year	447	732
Prior	2,546	2,526
Revolving line of credit arrangements	18,163	15,912
Loans, net of unearned income	50,097	44,798
Corporate loans | Non-investment grade, accrual | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	2,461	4,207
One year prior to current fiscal year	948	748
Two years prior to current fiscal year	568	1,084
Three years prior to current fiscal year	735	56
Four years prior to current fiscal year	39	194
Prior	491	260
Revolving line of credit arrangements	2,575	2,725
Loans, net of unearned income	7,817	9,274
Corporate loans | Non-investment grade, accrual | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	414	1,034
One year prior to current fiscal year	1,108	1,234
Two years prior to current fiscal year	1,729	1,378
Three years prior to current fiscal year	1,464	947
Four years prior to current fiscal year	918	755
Prior	1,205	1,016
Revolving line of credit arrangements	543	620
Loans, net of unearned income	7,381	6,984
Corporate loans | Non-investment grade, accrual | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	305	653
One year prior to current fiscal year	447	434
Two years prior to current fiscal year	366	248
Three years prior to current fiscal year	307	158
Four years prior to current fiscal year	136	211
Prior	317	155
Revolving line of credit arrangements	1,283	1,253
Loans, net of unearned income	3,161	3,112
Corporate loans | Non-investment grade, non-accrual | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	53
One year prior to current fiscal year	22	46
Two years prior to current fiscal year	44	84
Three years prior to current fiscal year	37	35
Four years prior to current fiscal year	4	45
Prior	76	93
Revolving line of credit arrangements	221	361
Loans, net of unearned income	404	717
Corporate loans | Non-investment grade, non-accrual | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	9	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	1	0
Revolving line of credit arrangements	28	51
Loans, net of unearned income	38	51
Corporate loans | Non-investment grade, non-accrual | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	3	118
One year prior to current fiscal year	5	233
Two years prior to current fiscal year	56	8
Three years prior to current fiscal year	30	38
Four years prior to current fiscal year	25	110
Prior	290	308
Revolving line of credit arrangements	45	53
Loans, net of unearned income	454	868
Corporate loans | Non-investment grade, non-accrual | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	4	8
One year prior to current fiscal year	0	0
Two years prior to current fiscal year	2	41
Three years prior to current fiscal year	16	0
Four years prior to current fiscal year	1	55
Prior	64	12
Revolving line of credit arrangements	15	130
Loans, net of unearned income	$ 102	$ 246