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Loans Held for Investment and Allowance for Credit Losses on Loans - Additional Information (Detail) - USD ($) | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2024 | Sep. 30, 2023 | Dec. 31, 2023
Financing Receivable Recorded Investment [Line Items] |  |  |
Gains (losses) on sale of property held in other real estate owned | $ 1,300,000 | $ 378,000 |
Interest income recognized on nonaccrual loans | 0 | 0 |
Interest income that would have been recognized | 2,600,000 | $ 1,100,000 |
Balance of modifies loans | 8,400,000 |  | $ 5,300,000
Commercial Real Estate |  |  |
Financing Receivable Recorded Investment [Line Items] |  |  |
Other real estate | 31,100,000 |  | 29,400,000
U.S. Federal Agencies [Member] |  |  |
Financing Receivable Recorded Investment [Line Items] |  |  |
Nonaccrual loans guaranteed by government agencies | $ 7,500,000 |  | $ 6,700,000
Parent Company [Member] |  |  |
Financing Receivable Recorded Investment [Line Items] |  |  |
Percentage of loans secured by real estate | 69.00% |  |
BancFirst [Member] |  |  |
Financing Receivable Recorded Investment [Line Items] |  |  |
Loan percentage | 84.00% |  |
Pegasus and Worthington [Member] |  |  |
Financing Receivable Recorded Investment [Line Items] |  |  |
Loan percentage | 16.00% |  |

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