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INVESTMENTS (Narrative) (Detail) - USD ($) | 3 Months Ended | 6 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2023 | Jun. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024 | Dec. 31, 2024
Schedule of Investments [Line Items] |  |  |  |  |  |  |
Trading securities | $ 5,581,000 |  |  |  | $ 5,581,000 |  | $ 5,243,000
AFS debt securities, allowance | 0 |  |  |  | 0 |  | 0
Net unrealized loss on debt securities, net of tax | 36,500,000 |  |  |  | 36,500,000 |  | 62,200,000
Deferred tax assets, unrealized losses on available for sale securities | 10,500,000 |  |  |  | 10,500,000 |  | 17,000,000
Provision for credit losses, HTM debt securities | 0 |  | $ 1,800,000 |  | 0 | $ (910,000) | 0
HTM debt securities, excluding accrued interest from amortized cost | 1,500,000 |  |  |  | 1,500,000 |  | 1,600,000
Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Recovery | 0 | $ 910,000 |  |  |  |  |
Write off, accrued interest, HTM debt securities |  | $ 910,000 |  |  |  |  |
Asset Pledged as Collateral |  |  |  |  |  |  |
Schedule of Investments [Line Items] |  |  |  |  |  |  |
AFS and HTM debt securities, amortized cost | 809,200,000 |  |  |  | 809,200,000 |  | 519,900,000
AFS and HTM debt securities, fair value | 762,400,000 |  |  |  | 762,400,000 |  | 449,000,000.0
Available-for-sale Securities |  |  |  |  |  |  |
Schedule of Investments [Line Items] |  |  |  |  |  |  |
Interest receivable | 2,500,000 |  |  |  | 2,500,000 |  | 1,700,000
Transferred Securities |  |  |  |  |  |  |
Schedule of Investments [Line Items] |  |  |  |  |  |  |
AFS debt securities transferred to HTM, fair value |  |  |  | $ 520,300,000 |  |  |
AFS debt securities, transfer, unrealized loss |  |  |  | $ 72,100,000 |  |  |
Net unrealized loss on debt securities, net of tax | (37,900,000) |  |  |  | (37,900,000) |  | (41,800,000)
Deferred tax assets, unrealized losses on available for sale securities | $ 11,000,000 |  |  |  | $ 11,000,000 |  | $ 11,400,000

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