LOANS - Corporate Loans Credit Quality Indicators (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Loans receivable
Loans, net of unearned income	$ 675,883	$ 699,483
Loans at fair value	6,854	4,085
Leases
Loans receivable
Loans, net of unearned income	700	1,400
Corporate
Loans receivable
Loans, net of unearned income	387,044	389,935
Total non-accrual	3,527	2,188
Loans at fair value	6,840	4,067
Corporate | Commercial and industrial
Loans receivable
Loans, net of unearned income	156,340	166,846
Total non-accrual	2,795	1,828
Corporate | Financial institutions
Loans receivable
Loans, net of unearned income	87,689	91,852
Total non-accrual	92	50
Corporate | Mortgage and real estate
Loans receivable
Loans, net of unearned income	72,038	63,151
Total non-accrual	505	188
Corporate | Leases
Loans receivable
Loans, net of unearned income	738	1,385
Total non-accrual	24	41
Corporate | Other
Loans receivable
Loans, net of unearned income	63,399	62,634
Total non-accrual	111	81
Corporate | Non-rated private bank loans managed on a delinquency basis
Loans receivable
2020	9,823
2019	7,121
2018	3,533
2017	3,674
2016	4,300
Prior	7,942
Revolving line of credit arrangements	0
Loans, net of unearned income	36,393	31,590
Corporate | Corporate loans, net of unearned income
Loans receivable
2020	107,122
2019	36,513
2018	29,628
2017	17,059
2016	11,340
Prior	32,195
Revolving line of credit arrangements	146,347
Loans, net of unearned income	387,044	389,935
Loans at fair value	6,840	4,067
Corporate | Investment Grade
Loans receivable
2020	66,625
2019	20,851
2018	17,806
2017	8,211
2016	4,767
Prior	17,709
Revolving line of credit arrangements	115,311
Loans, net of unearned income	251,280	277,056
Corporate | Investment Grade | Commercial and industrial
Loans receivable
2020	38,398
2019	7,607
2018	5,929
2017	3,909
2016	2,094
Prior	8,670
Revolving line of credit arrangements	25,819
Loans, net of unearned income	92,426	110,797
Corporate | Investment Grade | Financial institutions
Loans receivable
2020	10,560
2019	2,964
2018	2,106
2017	782
2016	681
Prior	2,030
Revolving line of credit arrangements	56,239
Loans, net of unearned income	75,362	80,533
Corporate | Investment Grade | Mortgage and real estate
Loans receivable
2020	6,793
2019	6,714
2018	5,174
2017	2,568
2016	1,212
Prior	1,719
Revolving line of credit arrangements	1,557
Loans, net of unearned income	25,737	27,571
Corporate | Investment Grade | Other
Loans receivable
2020	10,874
2019	3,566
2018	4,597
2017	952
2016	780
Prior	5,290
Revolving line of credit arrangements	31,696
Loans, net of unearned income	57,755	58,155
Corporate | Non-investment grade, accrual | Commercial and industrial
Loans receivable
2020	19,683
2019	4,794
2018	4,645
2017	2,883
2016	1,182
Prior	4,533
Revolving line of credit arrangements	23,400
Loans, net of unearned income	61,120	54,220
Corporate | Non-investment grade, accrual | Financial institutions
Loans receivable
2020	7,413
2019	700
2018	654
2017	274
2016	141
Prior	197
Revolving line of credit arrangements	2,855
Loans, net of unearned income	12,234	11,269
Corporate | Non-investment grade, accrual | Mortgage and real estate
Loans receivable
2020	1,882
2019	1,919
2018	2,058
2017	1,457
2016	697
Prior	837
Revolving line of credit arrangements	551
Loans, net of unearned income	9,401	3,811
Corporate | Non-investment grade, accrual | Other
Loans receivable
2020	1,407
2019	918
2018	725
2017	370
2016	186
Prior	657
Revolving line of credit arrangements	1,986
Loans, net of unearned income	6,249	5,734
Corporate | Non-investment grade, non-accrual | Commercial and industrial
Loans receivable
2020	260
2019	203
2018	192
2017	143
2016	57
Prior	223
Revolving line of credit arrangements	1,717
Total non-accrual	2,795	1,828
Corporate | Non-investment grade, non-accrual | Financial institutions
Loans receivable
2020	1
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving line of credit arrangements	91
Total non-accrual	92	50
Corporate | Non-investment grade, non-accrual | Mortgage and real estate
Loans receivable
2020	13
2019	4
2018	3
2017	18
2016	8
Prior	32
Revolving line of credit arrangements	427
Total non-accrual	505	188
Corporate | Non-investment grade, non-accrual | Other
Loans receivable
2020	15
2019	3
2018	12
2017	29
2016	2
Prior	65
Revolving line of credit arrangements	9
Total non-accrual	135	122
Corporate | Non-Investment Grade
Loans receivable
2020	30,674
2019	8,541
2018	8,289
2017	5,174
2016	2,273
Prior	6,544
Revolving line of credit arrangements	31,036
Loans, net of unearned income	$ 92,531	$ 77,222