LOANS - Consumer Loans and Ratios Outside of North America (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022	Jun. 30, 2022
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 660,612	$ 657,221
Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	374,591	368,067
Consumer | 30–89 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	2,572	2,372
Consumer | 90+ days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	2,454	2,153
Consumer | Classifiably managed
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	30,596	31,478
Consumer | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	102,680	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	152,352	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	36,242	36,812
Consumer | Personal, small business and other | Classifiably managed
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	30,596	31,478
In offices outside North America | Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 77,799	79,053
NCL ratio	1.12%		0.72%
In offices outside North America | Consumer | 30–89 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 336	$ 314
Past due ratio	0.56%	0.51%
In offices outside North America | Consumer | 90+ days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 321	$ 265
Past due ratio	0.54%	0.43%
In offices outside North America | Consumer | Classifiably managed
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 17,902	$ 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	59,897	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	79,300	80,500
In offices outside North America | Consumer | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 27,090	28,114
NCL ratio	(0.01%)		0.04%
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	$ 48	$ 62
Past due ratio	0.18%	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	$ 92	$ 106
Past due ratio	0.34%	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	27,090	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	20,400	19,800
In offices outside North America | Consumer | Credit cards
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 13,714	12,955
NCL ratio	3.98%		3.08%
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	$ 180	$ 147
Past due ratio	1.31%	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	$ 190	$ 149
Past due ratio	1.39%	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	13,714	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	$ 36,995	37,984
NCL ratio	0.91%		0.55%
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	$ 108	$ 105
Past due ratio	0.57%	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	$ 39	$ 10
Past due ratio	0.20%	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	$ 17,902	$ 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	19,093	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	26,000	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	17,900	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	$ 26,000	$ 26,600