LOANS - Corporate Loans Credit Quality Indicators (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	$ 676,834	$ 675,883
Loans held at fair value	7,707	6,854
Lease financing
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	600	700
Corporate
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	400,939	387,044
Total non-accrual	2,576	3,527
Loans held at fair value	7,693	6,840
Corporate | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	152,134	156,340
Total non-accrual	1,878	2,795
Corporate | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	100,989	87,689
Total non-accrual	39	92
Corporate | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	73,156	72,038
Total non-accrual	458	505
Corporate | Lease financing
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	602	738
Total non-accrual	22	24
Corporate | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	66,365	63,399
Total non-accrual	179	111
Corporate | Non-rated private bank loans managed on a delinquency basis
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	5,600	9,823
One year prior to current fiscal year	9,537	7,121
Two years prior to current fiscal year	6,551	3,533
Three years prior to current fiscal year	3,210	3,674
Four years prior to current fiscal year	3,248	4,300
Prior	10,043	7,942
Revolving line of credit arrangements	0	0
Total loans, net of unearned income	38,189	36,393
Corporate | Corporate loans, net of unearned income
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	91,572	107,122
One year prior to current fiscal year	40,794	36,513
Two years prior to current fiscal year	29,777	29,628
Three years prior to current fiscal year	23,864	17,059
Four years prior to current fiscal year	14,017	11,340
Prior	38,628	32,195
Revolving line of credit arrangements	154,594	146,347
Total loans, net of unearned income	400,939	387,044
Loans held at fair value	7,693	6,840
Corporate | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	62,964	66,625
One year prior to current fiscal year	23,677	20,851
Two years prior to current fiscal year	15,800	17,806
Three years prior to current fiscal year	14,649	8,211
Four years prior to current fiscal year	6,861	4,767
Prior	22,076	17,709
Revolving line of credit arrangements	127,410	115,311
Total loans, net of unearned income	273,437	251,280
Corporate | Investment grade | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	37,302	38,398
One year prior to current fiscal year	7,576	7,607
Two years prior to current fiscal year	5,592	5,929
Three years prior to current fiscal year	5,066	3,909
Four years prior to current fiscal year	3,302	2,094
Prior	9,628	8,670
Revolving line of credit arrangements	28,121	25,819
Total loans, net of unearned income	96,587	92,426
Corporate | Investment grade | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	12,951	10,560
One year prior to current fiscal year	4,271	2,964
Two years prior to current fiscal year	1,809	2,106
Three years prior to current fiscal year	1,409	782
Four years prior to current fiscal year	914	681
Prior	2,615	2,030
Revolving line of credit arrangements	66,706	56,239
Total loans, net of unearned income	90,675	75,362
Corporate | Investment grade | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	2,896	6,793
One year prior to current fiscal year	5,748	6,714
Two years prior to current fiscal year	5,845	5,174
Three years prior to current fiscal year	3,859	2,568
Four years prior to current fiscal year	2,010	1,212
Prior	3,204	1,719
Revolving line of credit arrangements	1,545	1,557
Total loans, net of unearned income	25,107	25,737
Corporate | Investment grade | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	9,815	10,874
One year prior to current fiscal year	6,082	3,566
Two years prior to current fiscal year	2,554	4,597
Three years prior to current fiscal year	4,315	952
Four years prior to current fiscal year	635	780
Prior	6,629	5,290
Revolving line of credit arrangements	31,038	31,696
Total loans, net of unearned income	61,068	57,755
Corporate | Non-investment grade, accrual | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	15,439	19,683
One year prior to current fiscal year	4,660	4,794
Two years prior to current fiscal year	3,892	4,645
Three years prior to current fiscal year	3,334	2,883
Four years prior to current fiscal year	2,304	1,182
Prior	4,020	4,533
Revolving line of credit arrangements	20,021	23,400
Total loans, net of unearned income	53,670	61,120
Corporate | Non-investment grade, accrual | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	5,008	7,413
One year prior to current fiscal year	936	700
Two years prior to current fiscal year	546	654
Three years prior to current fiscal year	334	274
Four years prior to current fiscal year	101	141
Prior	273	197
Revolving line of credit arrangements	3,076	2,855
Total loans, net of unearned income	10,274	12,234
Corporate | Non-investment grade, accrual | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	1,302	1,882
One year prior to current fiscal year	1,314	1,919
Two years prior to current fiscal year	2,133	2,058
Three years prior to current fiscal year	1,633	1,457
Four years prior to current fiscal year	1,045	697
Prior	1,304	837
Revolving line of credit arrangements	672	551
Total loans, net of unearned income	9,403	9,401
Corporate | Non-investment grade, accrual | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	1,127	1,407
One year prior to current fiscal year	456	918
Two years prior to current fiscal year	644	725
Three years prior to current fiscal year	516	370
Four years prior to current fiscal year	312	186
Prior	647	657
Revolving line of credit arrangements	1,995	1,986
Total loans, net of unearned income	5,697	6,249
Corporate | Non-investment grade, non-accrual | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	40	260
One year prior to current fiscal year	182	203
Two years prior to current fiscal year	201	192
Three years prior to current fiscal year	83	143
Four years prior to current fiscal year	108	57
Prior	172	223
Revolving line of credit arrangements	1,091	1,717
Total non-accrual	1,877	2,795
Corporate | Non-investment grade, non-accrual | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	1
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	11	0
Revolving line of credit arrangements	29	91
Total non-accrual	40	92
Corporate | Non-investment grade, non-accrual | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	2	13
One year prior to current fiscal year	13	4
Two years prior to current fiscal year	5	3
Three years prior to current fiscal year	85	18
Four years prior to current fiscal year	10	8
Prior	62	32
Revolving line of credit arrangements	280	427
Total non-accrual	457	505
Corporate | Non-investment grade, non-accrual | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	90	15
One year prior to current fiscal year	19	3
Two years prior to current fiscal year	5	12
Three years prior to current fiscal year	20	29
Four years prior to current fiscal year	28	2
Prior	20	65
Revolving line of credit arrangements	20	9
Total non-accrual	202	135
Corporate | Non-investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	23,008	30,674
One year prior to current fiscal year	7,580	8,541
Two years prior to current fiscal year	7,426	8,289
Three years prior to current fiscal year	6,005	5,174
Four years prior to current fiscal year	3,908	2,273
Prior	6,509	6,544
Revolving line of credit arrangements	27,184	31,036
Total loans, net of unearned income	$ 81,620	$ 92,531