LOANS AND ALLOWANCE FOR CREDIT LOSSES - Schedule of Loan Modifications (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Financing Receivable, Modified [Line Items]
Payment deferral and all other modifications	$ 1,378	$ 995	$ 3,066	$ 2,103
% of Total Class of Financing Receivable	0.96%	1.15%	2.13%	2.44%
Payment Deferral Only
Financing Receivable, Modified [Line Items]
Payment deferral and all other modifications	$ 1,006	$ 817	$ 2,370	$ 1,750
All Other Modifications
Financing Receivable, Modified [Line Items]
Payment deferral and all other modifications	372	178	696	353
Commercial \| CRE
Financing Receivable, Modified [Line Items]
Payment deferral and all other modifications	$ 420	$ 332	$ 1,163	$ 831
% of Total Class of Financing Receivable	1.80%	3.80%	5.00%	9.51%
Commercial \| CRE \| Payment Deferral Only
Financing Receivable, Modified [Line Items]
Payment deferral and all other modifications	$ 420	$ 278	$ 974	$ 671
Commercial \| CRE \| All Other Modifications
Financing Receivable, Modified [Line Items]
Payment deferral and all other modifications	0	54	189	160
Commercial \| C&I loans
Financing Receivable, Modified [Line Items]
Payment deferral and all other modifications	$ 427	$ 27	$ 468	$ 53
% of Total Class of Financing Receivable	1.32%	0.35%	1.45%	0.67%
Commercial \| C&I loans \| Payment Deferral Only
Financing Receivable, Modified [Line Items]
Payment deferral and all other modifications	$ 111	$ 16	$ 112	$ 24
Commercial \| C&I loans \| All Other Modifications
Financing Receivable, Modified [Line Items]
Payment deferral and all other modifications	316	11	356	29
Commercial \| Multifamily loans
Financing Receivable, Modified [Line Items]
Payment deferral and all other modifications	$ 82	$ 185	$ 299	$ 216
% of Total Class of Financing Receivable	0.48%	1.86%	1.76%	2.17%
Commercial \| Multifamily loans \| Payment Deferral Only
Financing Receivable, Modified [Line Items]
Payment deferral and all other modifications	$ 65	$ 117	$ 244	$ 142
Commercial \| Multifamily loans \| All Other Modifications
Financing Receivable, Modified [Line Items]
Payment deferral and all other modifications	17	68	55	74
Consumer \| Residential mortgages
Financing Receivable, Modified [Line Items]
Payment deferral and all other modifications	$ 1	$ 2	$ 7	$ 2
% of Total Class of Financing Receivable	0.01%	0.02%	0.05%	0.03%
Consumer \| Residential mortgages \| Payment Deferral Only
Financing Receivable, Modified [Line Items]
Payment deferral and all other modifications	$ 0	$ 0	$ 0	$ 0
Consumer \| Residential mortgages \| All Other Modifications
Financing Receivable, Modified [Line Items]
Payment deferral and all other modifications	1	2	7	2
Consumer \| Home equity loans and lines of credit
Financing Receivable, Modified [Line Items]
Payment deferral and all other modifications	$ 0	$ 1	$ 3	$ 2
% of Total Class of Financing Receivable	0.00%	0.05%	0.11%	0.12%
Consumer \| Home equity loans and lines of credit \| Payment Deferral Only
Financing Receivable, Modified [Line Items]
Payment deferral and all other modifications	$ 0	$ 0	$ 0	$ 0
Consumer \| Home equity loans and lines of credit \| All Other Modifications
Financing Receivable, Modified [Line Items]
Payment deferral and all other modifications	0	1	3	2
Consumer \| RICs and auto loans
Financing Receivable, Modified [Line Items]
Payment deferral and all other modifications	$ 448	$ 448	$ 1,126	$ 999
% of Total Class of Financing Receivable	1.02%	1.04%	2.56%	2.33%
Consumer \| RICs and auto loans \| Payment Deferral Only
Financing Receivable, Modified [Line Items]
Payment deferral and all other modifications	$ 410	$ 406	$ 1,040	$ 913
Consumer \| RICs and auto loans \| All Other Modifications
Financing Receivable, Modified [Line Items]
Payment deferral and all other modifications	$ 38	$ 42	$ 86	$ 86

Amortized cost excluding accrued interest, of financing receivable modified during period for debtor experiencing financial difficulty.

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