Subordinated Debt - Additional Information (Detail) - USD ($)		1 Months Ended		6 Months Ended
	Jun. 17, 2021	Mar. 31, 2004	Feb. 29, 2004	Jun. 30, 2023
Subordinated Notes due 2036 [Member] | Private Placement [Member]
Subordinated Borrowing [Line Items]
Interest rate of securities	3.50%
Debt instrument maturity date				Jun. 30, 2036
Aggregate principal amount	$ 60,000,000
Net proceeds from sale of notes	59,150,000
Commissions and offering expenses	$ 850,000
Debt instrument, redemption, description				the Company may redeem all, but not less than all, of the Subordinated Notes at any time upon the occurrence of a “Tier 2 Capital Event,” a “Tax Event” or an “Investment Company Event” (each as defined in the Subordinated Notes). Any such redemption is subject to obtaining the prior approval of the Board of Governors of the Federal Reserve System (or its designee). The redemption price with respect to any such redemption will be equal to 100% of the principal amount of the Subordinated Note, or portion thereof, to be redeemed, plus accrued but unpaid interest, if any, thereon to, but excluding, the redemption date.
Debt instrument, redemption price, percentage of principal amount to be redeemed				100.00%
Subordinated Notes due 2036 [Member] | Private Placement [Member] | Bear Interest at Fixed Rate of 3.50% [Member]
Subordinated Borrowing [Line Items]
Frequency of payment				payable semi-annually in arrears on June 30 and December 31 of each year
Debt instrument, payment terms				The Subordinated Notes will initially bear interest at a fixed rate of 3.50% per annum, from and including June 17, 2021 to but excluding June 30, 2031, payable semi-annually in arrears on June 30 and December 31 of each year, commencing December 31, 2021. Then, from and including June 30, 2031, to but excluding the maturity date, the Subordinated Notes will bear interest at a floating rate equal to the benchmark (initially, three-month term SOFR), reset quarterly, plus a spread of 229 basis points, payable quarterly in arrears on March 31, June 30, September 30 and December 31 of each year. The Subordinated Notes mature on June 30, 2036.
Fixed rate				3.50%
Debt instrument, commencing date				Dec. 31, 2021
Subordinated Notes due 2036 [Member] | Private Placement [Member] | Three-Month Term SOFR [Member]
Subordinated Borrowing [Line Items]
Frequency of payment				payable quarterly in arrears on March 31, June 30, September 30 and December 31 of each year.
Debt instrument, Basis point rate				2.29%
BancFirst Capital Trust Two [Member] | Subordinated Debentures Subject to Mandatory Redemption [Member]
Subordinated Borrowing [Line Items]
Interest rate of securities				7.20%
Junior subordinated notes assumed				$ 26,800,000
Frequency of payment				payable January 15, April 15, July 15 and October 15 of each year
Debt instrument maturity date				Mar. 31, 2034
BancFirst Capital Trust Two [Member] | Cumulative Preferred Stock [Member]
Subordinated Borrowing [Line Items]
Issue of securities		$ 1,000,000	$ 25,000,000
Cumulative trust preferred securities interest rate				7.20%