Segment Information - Results of Operations and Selected Financial Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Net interest income	$ 424,456	$ 373,673	$ 315,657
Provision for/(benefit from) credit losses	7,458	10,076	(8,690)
Noninterest income	185,408	183,747	170,032
Depreciation and amortization	22,189	22,048	20,041
Other expenses	310,269	287,864	265,940
Income before taxes	269,948	237,432	208,398
Total assets	12,372,042	12,387,863	9,405,612
Capital expenditures	22,504	19,785	27,251
Operating Segments [Member] | BancFirst Metropolitan Banks [Member]
Segment Reporting Information [Line Items]
Net interest income	120,226	97,728	77,840
Provision for/(benefit from) credit losses	4,836	2,186	(5,474)
Noninterest income	24,793	32,756	23,257
Depreciation and amortization	2,347	2,821	2,593
Other expenses	46,329	42,583	39,356
Income before taxes	91,507	82,894	64,622
Total assets	3,598,888	3,412,369	2,627,874
Capital expenditures	2,752	2,026	1,612
Operating Segments [Member] | BancFirst Community Banks [Member]
Segment Reporting Information [Line Items]
Net interest income	229,196	208,728	180,925
Provision for/(benefit from) credit losses	2,331	2,451	(4,694)
Noninterest income	70,824	72,385	65,600
Depreciation and amortization	10,514	10,453	10,483
Other expenses	123,554	117,248	110,574
Income before taxes	163,621	150,961	130,162
Total assets	7,012,905	6,886,066	5,821,220
Capital expenditures	5,156	10,146	7,390
Operating Segments [Member] | Pegasus [Member]
Segment Reporting Information [Line Items]
Net interest income	51,277	46,439	24,222
Provision for/(benefit from) credit losses	(328)	2,840	1,395
Noninterest income	1,646	1,026	1,448
Depreciation and amortization	804	789	782
Other expenses	20,084	19,013	15,317
Income before taxes	32,363	24,823	8,176
Total assets	1,280,618	1,404,033	1,045,699
Capital expenditures	528	311	363
Operating Segments [Member] | Worthington [Member]
Segment Reporting Information [Line Items]
Net interest income	17,395	14,919
Provision for/(benefit from) credit losses	564	(43)
Noninterest income	1,170	1,034
Depreciation and amortization	496	398
Other expenses	13,636	9,280
Income before taxes	3,869	6,318
Total assets	600,364	541,002
Capital expenditures	5,497	262
Operating Segments [Member] | Other Financial Services [Member]
Segment Reporting Information [Line Items]
Net interest income	4,164	8,065	35,244
Provision for/(benefit from) credit losses	79	(161)	109
Noninterest income	52,711	50,643	47,124
Depreciation and amortization	481	519	557
Other expenses	37,495	36,271	60,435
Income before taxes	18,820	22,079	21,267
Total assets	121,601	171,679	71,694
Capital expenditures	108	67	400
Operating Segments [Member] | Executive, Operations & Support [Member]
Segment Reporting Information [Line Items]
Net interest income	2,198	(2,226)	(3,295)
Provision for/(benefit from) credit losses	(24)	2,803	(26)
Noninterest income	250,968	223,844	203,005
Depreciation and amortization	7,547	7,068	5,626
Other expenses	70,293	64,325	41,199
Income before taxes	175,350	147,422	152,911
Total assets	1,307,714	1,473,443	1,201,974
Capital expenditures	8,463	6,973	17,486
Eliminations [Member]
Segment Reporting Information [Line Items]
Net interest income		20	721
Noninterest income	(216,704)	(197,941)	(170,402)
Other expenses	(1,122)	(856)	(941)
Income before taxes	(215,582)	(197,065)	(168,740)
Total assets	$ (1,550,048)	$ (1,500,729)	$ (1,362,849)