LOANS - Consumer Loans and Ratios Outside of North America (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 688,922	$ 689,362
Consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	389,151	389,197
Consumer loans | 30–89 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income		3,259
Consumer loans | 90+ days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income		3,233
In offices outside North America | Consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 74,106	76,039
NCL ratio	1.29%		1.24%
In offices outside North America | Consumer loans | 30–89 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 337	$ 364
Past due ratio	0.60%	0.62%
In offices outside North America | Consumer loans | 90+ days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 301	$ 336
Past due ratio	0.54%	0.57%
In offices outside North America | Consumer loans | Classifiably managed
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 18,156	$ 17,007
In offices outside North America | Consumer loans | FICO Score, Delinquency Managed Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	55,950	59,032
In offices outside North America | Consumer loans | Classifiably Managed and Delinquency Managed
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	76,200	77,500
In offices outside North America | Consumer loans | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 25,702	26,426
NCL ratio	0.03%		(0.01%)
In offices outside North America | Consumer loans | Residential mortgages | 30–89 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 40	$ 48
Past due ratio	0.16%	0.18%
In offices outside North America | Consumer loans | Residential mortgages | 90+ days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 59	$ 69
Past due ratio	0.23%	0.26%
In offices outside North America | Consumer loans | Residential mortgages | Classifiably managed
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 0	$ 0
In offices outside North America | Consumer loans | Residential mortgages | FICO Score, Delinquency Managed Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	25,702	26,426
In offices outside North America | Consumer loans | Residential mortgages | Global Wealth Management Business
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	20,000	19,900
In offices outside North America | Consumer loans | Credit cards
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 12,930	14,233
NCL ratio	4.68%		4.35%
In offices outside North America | Consumer loans | Credit cards | 30–89 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 194	$ 209
Past due ratio	1.50%	1.47%
In offices outside North America | Consumer loans | Credit cards | 90+ days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 204	$ 227
Past due ratio	1.58%	1.59%
In offices outside North America | Consumer loans | Credit cards | Classifiably managed
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 0	$ 0
In offices outside North America | Consumer loans | Credit cards | FICO Score, Delinquency Managed Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	12,930	14,233
In offices outside North America | Consumer loans | Personal, small business and other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 35,474	$ 35,380
NCL ratio	0.95%		0.99%
In offices outside North America | Consumer loans | Personal, small business and other | Internal Investment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Percentage of loans rated investment grade		92.00%
In offices outside North America | Consumer loans | Personal, small business and other | 30–89 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 103	$ 107
Past due ratio	0.59%	0.58%
In offices outside North America | Consumer loans | Personal, small business and other | 90+ days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 38	$ 40
Past due ratio	0.22%	0.22%
In offices outside North America | Consumer loans | Personal, small business and other | Classifiably managed
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 18,156	$ 17,007
In offices outside North America | Consumer loans | Personal, small business and other | FICO Score, Delinquency Managed Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	17,318	18,373
In offices outside North America | Consumer loans | Personal, small business and other | Global Wealth Management Business
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 26,300	$ 24,900
In offices outside North America | Consumer loans | Personal, small business and other | Global Wealth Management Business | Internal Investment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Percentage of loans rated investment grade	58.00%	74.00%
In offices outside North America | Consumer loans | Personal, small business and other | Global Wealth Management Business | Classifiably managed
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income		$ 17,000
In offices outside North America | Consumer loans | 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	$ 24,900