Stockholders' Equity - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2021	Dec. 31, 2020	Jan. 01, 2022	Jun. 17, 2021
Stockholders Equity [Line Items]
Additional shares to repurchase	650,000
Increase to retained earnings for cumulative effect of adopting ASU		$ 977,067,000	$ 871,161,000
Subordinated Notes due 2036 [Member] | Private Placement [Member]
Stockholders Equity [Line Items]
Aggregate principal amount					$ 60,000,000
Small Business Administration (SBA), CARES Act, Paycheck Protection Program Lending Facility [Member]
Stockholders Equity [Line Items]
Percentage of risk weight under risk based capital rules		0.00%
Cumulative Effect Period of Adoption Adjustment [Member]
Stockholders Equity [Line Items]
Increase to retained earnings for cumulative effect of adopting ASU			$ 2,300,000
Accounting Standards Update [Extensible List]			ASC 326 [Member]
Maximum [Member]
Stockholders Equity [Line Items]
Quantitative limit for trust preferred securities to be included in tier 1 capital		$ 15,000,000,000
Subsequent Event [Member]
Stockholders Equity [Line Items]
Available equity of BancFirst for dividend payments to the company				$ 153,300,000
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%