LOANS - Consumer Loans and Ratios Outside of North America (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 651,995	$ 657,221
Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	363,696	368,067
Consumer | 30–89 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	2,325	2,372
Consumer | 90+ days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	2,375	2,153
Consumer | Classifiably managed
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	31,452	31,478
Consumer | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	98,790	96,039
Consumer | Residential mortgages | Classifiably managed
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	0
Consumer | Credit cards
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	145,023	150,098
Consumer | Credit cards | Classifiably managed
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	0
Consumer | Personal, small business and other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	36,877	36,812
Consumer | Personal, small business and other | Classifiably managed
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	31,452	31,478
In offices outside North America | Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 77,307	79,053
NCL ratio	1.09%		0.81%
In offices outside North America | Consumer | 30–89 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 315	$ 314
Past due ratio	0.53%	0.51%
In offices outside North America | Consumer | 90+ days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 285	$ 265
Past due ratio	0.48%	0.43%
In offices outside North America | Consumer | Classifiably managed
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 17,808	$ 17,762
In offices outside North America | Consumer | FICO Score, Delinquency Managed Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	59,499	61,291
In offices outside North America | Consumer | Classifiably Managed and Delinquency Managed
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	78,800	80,500
In offices outside North America | Consumer | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 26,913	28,114
NCL ratio	0.11%		0.09%
In offices outside North America | Consumer | Residential mortgages | 30–89 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 62	$ 62
Past due ratio	0.23%	0.22%
In offices outside North America | Consumer | Residential mortgages | 90+ days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 111	$ 106
Past due ratio	0.41%	0.38%
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	26,913	28,114
In offices outside North America | Consumer | Residential mortgages | Global Wealth Management Business
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	20,300	19,800
In offices outside North America | Consumer | Credit cards
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 13,033	12,955
NCL ratio	3.80%		3.23%
In offices outside North America | Consumer | Credit cards | 30–89 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 163	$ 147
Past due ratio	1.25%	1.13%
In offices outside North America | Consumer | Credit cards | 90+ days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 166	$ 149
Past due ratio	1.27%	1.15%
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	13,033	12,955
In offices outside North America | Consumer | Personal, small business and other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 37,361	37,984
NCL ratio	0.87%		0.63%
In offices outside North America | Consumer | Personal, small business and other | 30–89 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 90	$ 105
Past due ratio	0.46%	0.52%
In offices outside North America | Consumer | Personal, small business and other | 90+ days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 8	$ 10
Past due ratio	0.04%	0.05%
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	$ 17,808	$ 17,762
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	19,553	20,222
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	26,300	26,600
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	17,800	17,800
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	$ 26,300	$ 26,600