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Loans Held-for-Investment and Allowance for Credit Losses - Additional Information (Detail) - USD ($) | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024 | Dec. 31, 2024
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Nonaccrual, past due 90 days or more and still accruing, restructured loans and foreclosed assets | $ 58,542,000 | $ 64,417,000 | $ 58,542,000 | $ 64,417,000 | $ 63,096,000
Additional funds advanced in connection with impaired loans | 0 |  | 0 |  |
Loans held by subsidiaries subject to blanket liens | 7,391,570,000 |  | 7,391,570,000 |  |
Reserve for unfunded commitments (Other liabilities) | 8,842,000 | 8,004,000 | 8,842,000 | 8,004,000 | $ 8,677,000
Provision for loan losses | 25,506,000 | 5,552,000 | 30,929,000 | 12,718,000 |
Unfunded Loan Commitment [Member] |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Provision for loan losses | 24,435,000 | 6,123,000 | 31,095,000 | 12,817,000 |
Reversal of Provision for credit losses | $ 1,072,000 | $ 571,000 | $ 165,000 | $ 101,000 |

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