Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Jan. 31, 2024	Dec. 31, 2022	Jun. 17, 2021
Stockholders Equity [Line Items]
Increase to retained earnings for cumulative effect of adopting ASU	$ 1,276,305		$ 1,120,292
Subordinated Notes due 2036 [Member] | Private Placement [Member]
Stockholders Equity [Line Items]
Aggregate principal amount				$ 60,000
Maximum [Member]
Stockholders Equity [Line Items]
Quantitative limit for trust preferred securities to be included in tier 1 capital	$ 15,000,000
Subsequent Event [Member]
Stockholders Equity [Line Items]
Available equity of BancFirst for dividend payments to the company		$ 145,700
Senior Preferred Stock [Member]
Stockholders Equity [Line Items]
Preferred stock, shares issued	0		0
Preferred stock, shares outstanding			0
Cumulative Preferred Stock [Member]
Stockholders Equity [Line Items]
Preferred stock, shares issued	0		0
Preferred stock, shares outstanding	0
Dividend payable at redemption, per share	$ 5.00
Cumulative preferred stock dividend rate	10.00%