LOANS - Consumer Loans Outside of North America (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021	Jun. 30, 2021
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 657,333	$ 667,767
Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	355,605	376,534
Consumer | 30 to 89 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	1,728	1,999
Consumer | 90 days or more past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	1,776	1,963
Consumer | Classifiably Managed
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	33,935	35,324
Consumer | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	88,662	83,361
Consumer | Residential mortgages | Classifiably Managed
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	0	0
Consumer | Credit cards
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	136,854	133,351
Consumer | Credit cards | Classifiably Managed
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	0	0
Consumer | Personal, small business and other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	38,457	39,806
Consumer | Personal, small business and other | Classifiably Managed
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	33,935	35,324
In offices outside North America | Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 85,021	112,847
NCL ratio	0.72%		1.39%
In offices outside North America | Consumer | 30 to 89 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 277	$ 502
Past due ratio	0.43%	0.57%
In offices outside North America | Consumer | 90 days or more past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 286	$ 421
Past due ratio	0.45%	0.48%
In offices outside North America | Consumer | Classifiably Managed
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 20,889	$ 24,482
In offices outside North America | Consumer | FICO Score, Delinquency Managed Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	64,132	88,365
In offices outside North America | Consumer | Classifiably Managed and Delinquency Managed
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	86,600	114,300
In offices outside North America | Consumer | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 28,129	37,889
NCL ratio	0.04%		0.10%
In offices outside North America | Consumer | Residential mortgages | 30 to 89 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 50	$ 165
Past due ratio	0.18%	0.44%
In offices outside North America | Consumer | Residential mortgages | 90 days or more past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 91	$ 158
Past due ratio	0.32%	0.42%
In offices outside North America | Consumer | Residential mortgages | Classifiably Managed
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 0	$ 0
In offices outside North America | Consumer | Residential mortgages | FICO Score, Delinquency Managed Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	28,129	37,889
In offices outside North America | Consumer | Residential mortgages | Global Wealth Management Business
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	19,600	19,800
In offices outside North America | Consumer | Credit cards
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 11,858	17,808
NCL ratio	3.08%		5.09%
In offices outside North America | Consumer | Credit cards | 30 to 89 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 123	$ 192
Past due ratio	1.04%	1.08%
In offices outside North America | Consumer | Credit cards | 90 days or more past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 125	$ 188
Past due ratio	1.05%	1.06%
In offices outside North America | Consumer | Credit cards | Classifiably Managed
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 0	$ 0
In offices outside North America | Consumer | Credit cards | FICO Score, Delinquency Managed Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	11,858	17,808
In offices outside North America | Consumer | Personal, small business and other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 45,034	57,150
NCL ratio	0.55%		1.04%
In offices outside North America | Consumer | Personal, small business and other | 30 to 89 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 104	$ 145
Past due ratio	0.43%	0.44%
In offices outside North America | Consumer | Personal, small business and other | 90 days or more past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 70	$ 75
Past due ratio	0.29%	0.23%
In offices outside North America | Consumer | Personal, small business and other | Classifiably Managed
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 20,889	$ 24,482
In offices outside North America | Consumer | Personal, small business and other | FICO Score, Delinquency Managed Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	24,145	32,668
In offices outside North America | Consumer | Personal, small business and other | Global Wealth Management Business
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	30,600	34,600
In offices outside North America | Consumer | Personal, small business and other | Global Wealth Management Business | Classifiably Managed
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	20,900	24,500
In offices outside North America | Consumer | Personal, small business and other | Global Wealth Management Business | Classifiably Managed and Delinquency Managed
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 30,600	$ 34,600