VARIABLE INTEREST ENTITIES - Schedule of Variable Interest Entities (Details) - USD ($) $ in Millions	Sep. 30, 2026	Dec. 31, 2025
Variable Interest Entity [Line Items]
Total affordable housing tax credit and other unconsolidated investments (maximum loss exposure)	$ 241,182	$ 229,698
Liabilities for commitments to fund tax credit investments	219,605	207,460
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Total affordable housing tax credit and other unconsolidated investments (maximum loss exposure)	2,697	2,955
Variable Interest Entity, Not Primary Beneficiary \| Total tax credit equity investments
Variable Interest Entity [Line Items]
Total affordable housing tax credit and other unconsolidated investments (maximum loss exposure)	2,450	2,761
Variable Interest Entity, Not Primary Beneficiary \| Affordable housing tax credit investments
Variable Interest Entity [Line Items]
Total affordable housing tax credit and other unconsolidated investments (maximum loss exposure)	2,437	2,761
Variable Interest Entity, Not Primary Beneficiary \| Other tax credit investments
Variable Interest Entity [Line Items]
Total affordable housing tax credit and other unconsolidated investments (maximum loss exposure)	13	0
Variable Interest Entity, Not Primary Beneficiary \| Other unconsolidated investments
Variable Interest Entity [Line Items]
Total affordable housing tax credit and other unconsolidated investments (maximum loss exposure)	229	194
Variable Interest Entity, Not Primary Beneficiary \| Tax credit and other unconsolidated VIE investments
Variable Interest Entity [Line Items]
Total affordable housing tax credit and other unconsolidated investments (maximum loss exposure)	2,679	2,955
Variable Interest Entity, Not Primary Beneficiary \| Investment Securities Available For Sale
Variable Interest Entity [Line Items]
Total affordable housing tax credit and other unconsolidated investments (maximum loss exposure)	18	0
Variable Interest Entity, Not Primary Beneficiary \| Liabilities for commitments to fund tax credit investments
Variable Interest Entity [Line Items]
Liabilities for commitments to fund tax credit investments	1,096	$ 1,321
Variable Interest Entity, Not Primary Beneficiary \| NMTC Investment
Variable Interest Entity [Line Items]
Total affordable housing tax credit and other unconsolidated investments (maximum loss exposure)	$ 2