LOANS - Consumer Loans and Ratios Outside of North America (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024	Sep. 30, 2024
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 733,905	$ 694,488
Consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	398,628	393,102
In offices outside North America | Consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 77,441	71,378
NCL ratio	1.67%		1.29%
In offices outside North America | Consumer loans | 30–89 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 403	$ 328
Past due ratio	0.72%	0.61%
In offices outside North America | Consumer loans | 90+ days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 399	$ 310
Past due ratio	0.71%	0.58%
In offices outside North America | Consumer loans | Classifiably managed
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 21,562	$ 17,553
In offices outside North America | Consumer loans | Delinquency-managed loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	55,879	53,825
In offices outside North America | Consumer loans | Classifiably Managed and Delinquency Managed
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	79,400	72,500
In offices outside North America | Consumer loans | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 24,078	24,456
NCL ratio	0.10%		0.03%
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	$ 46	$ 38
Past due ratio	0.19%	0.16%
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	$ 73	$ 60
Past due ratio	0.30%	0.25%
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 | Delinquency-managed loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	24,078	24,456
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	18,700	19,100
In offices outside North America | Consumer loans | Credit cards
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 13,754	12,927
NCL ratio	5.98%		4.68%
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	$ 238	$ 190
Past due ratio	1.73%	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	$ 286	$ 214
Past due ratio	2.08%	1.66%
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 | Delinquency-managed loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	13,754	12,927
In offices outside North America | Consumer loans | Personal, small business and other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 39,609	$ 33,995
NCL ratio	1.09%		0.95%
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		83.00%
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	$ 119	$ 100
Past due ratio	0.66%	0.61%
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	$ 40	$ 36
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	$ 21,562	$ 17,553
In offices outside North America | Consumer loans | Personal, small business and other | Delinquency-managed loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	18,047	16,442
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	$ 30,000	$ 25,400
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	54.00%	56.00%
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		$ 17,600
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		$ 25,400