LOANS - Consumer Loans and Ratios Outside of North America (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 687,722	$ 689,362
Consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	386,117	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	$ 73,322	76,039
NCL ratio	1.33%		1.12%
In offices outside North America | Consumer loans | 30–89 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 323	$ 364
Past due ratio	0.58%	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	$ 306	$ 336
Past due ratio	0.55%	0.57%
In offices outside North America | Consumer loans | Classifiably managed
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 17,472	$ 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	55,850	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	74,700	77,500
In offices outside North America | Consumer loans | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 25,489	26,426
NCL ratio	0.04%		(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	$ 65	$ 69
Past due ratio	0.26%	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	25,489	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	19,600	19,900
In offices outside North America | Consumer loans | Credit cards
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 13,197	14,233
NCL ratio	4.70%		3.98%
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	$ 187	$ 209
Past due ratio	1.42%	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	$ 205	$ 227
Past due ratio	1.55%	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	13,197	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	$ 34,636	35,380
NCL ratio	0.96%		0.91%
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	$ 96	$ 107
Past due ratio	0.56%	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	$ 36	$ 40
Past due ratio	0.21%	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	$ 17,472	$ 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	17,164	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	25,000	24,900
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	$ 25,000	$ 24,900