Segment Information - Results of Operations and Selected Financial Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Net interest income	$ 373,673	$ 315,657	$ 306,668
Provision for/(benefit from) credit losses	10,076	(8,690)	62,648
Noninterest income	183,747	170,032	137,222
Depreciation and amortization	22,048	20,041	18,424
Other expenses	287,864	265,940	239,306
Income before taxes	237,432	208,398	123,512
Total assets	12,387,863	9,405,612	9,212,357
Capital expenditures	19,785	27,251	66,446
Operating Segments [Member] | BancFirst Metropolitan Banks [Member]
Segment Reporting Information [Line Items]
Net interest income	97,728	77,840	85,464
Provision for/(benefit from) credit losses	2,186	(5,474)	30,202
Noninterest income	32,756	23,257	18,664
Depreciation and amortization	2,821	2,593	2,639
Other expenses	42,583	39,356	36,746
Income before taxes	82,894	64,622	34,541
Total assets	3,412,369	2,627,874	2,729,886
Capital expenditures	2,026	1,612	1,087
Operating Segments [Member] | BancFirst Community Banks [Member]
Segment Reporting Information [Line Items]
Net interest income	208,728	180,925	175,757
Provision for/(benefit from) credit losses	2,451	(4,694)	29,827
Noninterest income	72,385	65,600	60,386
Depreciation and amortization	10,453	10,483	10,603
Other expenses	117,248	110,574	111,341
Income before taxes	150,961	130,162	84,372
Total assets	6,886,066	5,821,220	5,527,611
Capital expenditures	10,146	7,390	9,946
Operating Segments [Member] | Pegasus [Member]
Segment Reporting Information [Line Items]
Net interest income	46,439	24,222	21,360
Provision for/(benefit from) credit losses	2,840	1,395	1,916
Noninterest income	1,026	1,448	1,071
Depreciation and amortization	789	782	760
Other expenses	19,013	15,317	13,831
Income before taxes	24,823	8,176	5,924
Total assets	1,404,033	1,045,699	919,572
Capital expenditures	311	363	1,775
Operating Segments [Member] | Worthington [Member]
Segment Reporting Information [Line Items]
Net interest income	14,919
Provision for/(benefit from) credit losses	(43)
Noninterest income	1,034
Depreciation and amortization	398
Other expenses	9,280
Income before taxes	6,318
Total assets	541,002
Capital expenditures	262
Operating Segments [Member] | Other Financial Services [Member]
Segment Reporting Information [Line Items]
Net interest income	8,065	35,244	23,500
Provision for/(benefit from) credit losses	(161)	109	562
Noninterest income	50,643	47,124	41,549
Depreciation and amortization	519	557	500
Other expenses	36,271	60,435	44,918
Income before taxes	22,079	21,267	19,069
Total assets	171,679	71,694	137,122
Capital expenditures	67	400	450
Operating Segments [Member] | Executive, Operations & Support [Member]
Segment Reporting Information [Line Items]
Net interest income	(2,226)	(3,295)	79
Provision for/(benefit from) credit losses	2,803	(26)	141
Noninterest income	223,844	203,005	118,491
Depreciation and amortization	7,068	5,626	3,922
Other expenses	64,325	41,199	33,588
Income before taxes	147,422	152,911	80,919
Total assets	1,473,443	1,201,974	1,073,507
Capital expenditures	6,973	17,486	53,188
Eliminations [Member]
Segment Reporting Information [Line Items]
Net interest income	20	721	508
Noninterest income	(197,941)	(170,402)	(102,939)
Other expenses	(856)	(941)	(1,118)
Income before taxes	(197,065)	(168,740)	(101,313)
Total assets	$ (1,500,729)	$ (1,362,849)	$ (1,175,341)