INVESTMENT SECURITIES - Schedule of Carrying Value of Investment Securities (Details) - USD ($) $ in Millions |
Sep. 30, 2026 |
Dec. 31, 2025 |
|---|---|---|
| Financial Instruments Owned and Pledged as Collateral [Line Items] | ||
| Total collateral pledged | $ 15,105 | $ 11,301 |
| Pledged against public fund deposits | ||
| Financial Instruments Owned and Pledged as Collateral [Line Items] | ||
| Total collateral pledged | 6,387 | 2,267 |
| Pledged against borrowing capacity with the FRB | ||
| Financial Instruments Owned and Pledged as Collateral [Line Items] | ||
| Total collateral pledged | 3,611 | 4,270 |
| Pledged against repurchase agreements and supported hedging relationships, recourse on loans, and other agreements | ||
| Financial Instruments Owned and Pledged as Collateral [Line Items] | ||
| Total collateral pledged | 551 | 336 |
| Pledged against borrowing capacity with the FHLB | ||
| Financial Instruments Owned and Pledged as Collateral [Line Items] | ||
| Total collateral pledged | $ 4,556 | $ 4,428 |