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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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Percentage of loans secured by real estate.

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The net gain (loss) resulting from sales and other disposals of other real estate owned, increases (decreases) in the valuation allowance for foreclosed real estate, and write-downs of other real estate owned after acquisition or physical possession.

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