LOANS - Corporate Loans (Details) $ in Millions	3 Months Ended
Mar. 31, 2026 USD ($) category	Dec. 31, 2025 USD ($)
Receivables [Abstract]
Number of loan categories \| category	2
Loans
Unallocated portfolio layer cumulative basis adjustments		$ 17
Loans, net of unearned income	$ 761,616	752,230
Lease financing
Loans
Loans, net of unearned income	100	100
Corporate loans
Loans
Corporate loans, net of unearned income, excluding portfolio layer cumulative basis adjustments	359,217	343,680
Unallocated portfolio layer cumulative basis adjustments	8	17
Loans, net of unearned income	359,225	343,697
Unearned income	(1,100)	(1,100)
Accrued interest receivable	2,000	2,000
Loans sold and/or reclassified to held-for-sale	1,000
Corporate loans \| In North America offices
Loans
Corporate loans, net of unearned income, excluding portfolio layer cumulative basis adjustments	178,953	170,667
Corporate loans \| In North America offices \| Commercial and industrial
Loans
Corporate loans, net of unearned income, excluding portfolio layer cumulative basis adjustments	63,758	57,406
Corporate loans \| In North America offices \| Financial institutions
Loans
Corporate loans, net of unearned income, excluding portfolio layer cumulative basis adjustments	74,066	72,154
Corporate loans \| In North America offices \| Mortgage and real estate
Loans
Corporate loans, net of unearned income, excluding portfolio layer cumulative basis adjustments	18,191	17,931
Corporate loans \| In North America offices \| Installment and other
Loans
Corporate loans, net of unearned income, excluding portfolio layer cumulative basis adjustments	22,866	23,104
Corporate loans \| In North America offices \| Lease financing
Loans
Corporate loans, net of unearned income, excluding portfolio layer cumulative basis adjustments	72	72
Corporate loans \| In offices outside North America
Loans
Corporate loans, net of unearned income, excluding portfolio layer cumulative basis adjustments	180,264	173,013
Corporate loans \| In offices outside North America \| Commercial and industrial
Loans
Corporate loans, net of unearned income, excluding portfolio layer cumulative basis adjustments	100,839	96,886
Corporate loans \| In offices outside North America \| Financial institutions
Loans
Corporate loans, net of unearned income, excluding portfolio layer cumulative basis adjustments	29,480	27,054
Corporate loans \| In offices outside North America \| Mortgage and real estate
Loans
Corporate loans, net of unearned income, excluding portfolio layer cumulative basis adjustments	9,823	9,856
Corporate loans \| In offices outside North America \| Installment and other
Loans
Corporate loans, net of unearned income, excluding portfolio layer cumulative basis adjustments	34,469	34,100
Corporate loans \| In offices outside North America \| Lease financing
Loans
Corporate loans, net of unearned income, excluding portfolio layer cumulative basis adjustments	44	47
Corporate loans \| In offices outside North America \| Government and official institutions
Loans
Corporate loans, net of unearned income, excluding portfolio layer cumulative basis adjustments	$ 5,609	$ 5,070

Financing Receivable, before Allowance for Credit Loss, Excluding Portfolio Layer Cumulative Basis Adjustments

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The number of loan categories reported by the entity.

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Amount of fee received for commitment to originate or purchase financing receivable where likelihood of commitment being exercised is remote, to be recognized as service income.

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