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INVESTMENT SECURITIES (Narrative) (Details) | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2025 USD ($) security | Sep. 30, 2024 USD ($) | Sep. 30, 2025 USD ($) security | Sep. 30, 2024 USD ($) | Dec. 31, 2024 USD ($) security
Marketable Securities [Line Items] |  |  |  |  |
Accrued interest receivable | $ 57,000,000 |  | $ 57,000,000 |  | $ 60,000,000
Investment securities | 19,438,000,000 |  | 19,438,000,000 |  | $ 20,270,000,000
Unrealized loss amortization associated with the securities transferred from AFS to HTM | $ 47,000,000 | $ 51,000,000 | $ 137,000,000 | $ 147,000,000 |
Number of AFS investment securities in an unrealized loss position | security | 2,135 |  | 2,135 |  | 2,534
Available-for-sale, realized gain (loss) | $ 0 | $ 0 | $ 0 | $ 0 |
Allowance for credit loss on HTM securities (less than) | 1,000,000 |  | 1,000,000 |  |
Fixed-Rate Available For Sale Securities |  |  |  |  |
Marketable Securities [Line Items] |  |  |  |  |
Unrealized loss amortization associated with the securities transferred from AFS to HTM, before tax |  |  | 1,700,000,000 |  | $ 1,800,000,000
Unrealized loss amortization associated with the securities transferred from AFS to HTM |  |  | 1,200,000,000 |  | 1,400,000,000
Asset Pledged as Collateral |  |  |  |  |
Marketable Securities [Line Items] |  |  |  |  |
Investment securities | $ 17,400,000,000 |  | $ 17,400,000,000 |  | $ 17,900,000,000

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