Stock-Based Compensation - Additional Information (Detail) - USD ($) $ in Thousands			9 Months Ended
	Jun. 01, 2023	May 25, 2023	Sep. 30, 2023	Sep. 30, 2022
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option granted			0
Net cash settlement for stock options, cost			$ 0	$ 0
Deferred board fees percentage for stock units accumulation			100.00%
RSU's Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares for future grants		490,925
Option exercisable rate		20.00%
Option exercisable period		2 years
Options expire period		10 years
Options vest and exercisable Description			The restricted stock units ("RSU's") vest beginning two years from the date of grant at the rate of 20% per year for five years.
Vesting period in years		5 years
Employee Plan [Member] | Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option plan termination date	Jun. 01, 2023
Option exercisable rate			25.00%
Option exercisable period			4 years
Options expire period			15 years
Vesting period in years, start			4 years
Options vest and exercisable Description			and are exercisable beginning four years from the date of grant at the rate of 25% per year for four years, and expire no later than the end of fifteen years from the date of grant
Vesting period in years			5 years
Employee Plan [Member] | RSU's Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period in years			6 years
Non-Employee Directors Stock Option Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option plan termination date	Jun. 01, 2023
Option exercisable rate			25.00%
Option exercisable period			1 year
Options expire period			15 years
Options vest and exercisable Description			The remaining options will continue to vest and are exercisable beginning one year from the date of grant at the rate of 25% per year for four years
Vesting period in years			4 years
Banc First Deferred Stock Compensation Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option plan termination date			Dec. 31, 2024
Number of shares available for future issuance under deferred compensation plan			20,262
Number of shares of common stock distributed			18,136	16,684