Intangible Assets and Goodwill - Summary of Goodwill by Business Segment (Detail) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
Goodwill [Line Items]
Balance at beginning and end of period	$ 182,263	$ 182,263
BancFirst Metropolitan Banks [Member]
Goodwill [Line Items]
Balance at beginning and end of period	13,767
BancFirst Community Banks [Member]
Goodwill [Line Items]
Balance at beginning and end of period	61,420
Pegasus [Member]
Goodwill [Line Items]
Balance at beginning and end of period	68,855
Worthington [Member]
Goodwill [Line Items]
Balance at beginning and end of period	32,133
Other Financial Services [Member]
Goodwill [Line Items]
Balance at beginning and end of period	5,464
Executive, Operations & Support [Member]
Goodwill [Line Items]
Balance at beginning and end of period	$ 624