Intangible Assets and Goodwill - Summary of Goodwill by Business Segment (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2023 USD ($)
Goodwill [Line Items]
Balance at beginning of period	$ 182,055
Acquisitions	208
Balance at end of period	182,263
BancFirst Metropolitan Banks [Member]
Goodwill [Line Items]
Balance at beginning of period	13,767
Balance at end of period	13,767
BancFirst Community Banks [Member]
Goodwill [Line Items]
Balance at beginning of period	61,212
Acquisitions	208
Balance at end of period	61,420
Pegasus [Member]
Goodwill [Line Items]
Balance at beginning of period	68,855
Balance at end of period	68,855
Worthington [Member]
Goodwill [Line Items]
Balance at beginning of period	32,133
Balance at end of period	32,133
Other Financial Services [Member]
Goodwill [Line Items]
Balance at beginning of period	5,464
Balance at end of period	5,464
Executive, Operations & Support [Member]
Goodwill [Line Items]
Balance at beginning of period	624
Balance at end of period	$ 624