Loans Held for Investment and Allowance for Loan Losses - Changes in Allowance for Loan Losses (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 89,562,000	$ 80,818,000	$ 88,734,000	$ 75,834,000
Provision for loan losses	5,910,000	6,522,000	7,166,000	11,229,000
Recoveries	400,000	319,000	822,000	884,000
Charge-offs	(702,000)	(1,118,000)	(1,552,000)	(1,406,000)
Ending balance	95,170,000	86,541,000	95,170,000	86,541,000
C&I [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	16,106,000	16,083,000	15,698,000	16,129,000
Provision for loan losses	(790,000)	988,000	(289,000)	924,000
Recoveries	177,000	113,000	288,000	165,000
Charge-offs	(242,000)	(654,000)	(446,000)	(688,000)
Ending balance	15,251,000	16,530,000	15,251,000	16,530,000
Municipal [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	195,000	1,067,000	195,000	1,026,000
Provision for loan losses	44,000	(880,000)	44,000	(839,000)
Recoveries	0	0	0	0
Charge-offs	0	0	0	0
Ending balance	239,000	187,000	239,000	187,000
Agriculture [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	3,243,000	1,214,000	1,281,000	1,041,000
Provision for loan losses	(1,359,000)	(153,000)	658,000	(181,000)
Recoveries	46,000	21,000	51,000	222,000
Charge-offs	1,000	0	(59,000)	0
Ending balance	1,931,000	1,082,000	1,931,000	1,082,000
Construction & Development [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	24,811,000	28,627,000	28,553,000	26,443,000
Provision for loan losses	(1,300,000)	339,000	(5,009,000)	2,423,000
Recoveries	0	0	0	100,000
Charge-offs	0	0	(33,000)	0
Ending balance	23,511,000	28,966,000	23,511,000	28,966,000
Farm [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	2,517,000	1,937,000	2,914,000	1,957,000
Provision for loan losses	385,000	867,000	(12,000)	847,000
Recoveries	0	0	0	0
Charge-offs	0	0	0	0
Ending balance	2,902,000	2,804,000	2,902,000	2,804,000
Non-Owner Occupied CRE [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	14,968,000	9,051,000	13,425,000	9,075,000
Provision for loan losses	(1,951,000)	4,398,000	(415,000)	4,349,000
Recoveries	24,000	22,000	31,000	47,000
Charge-offs	(13,000)	0	(13,000)	0
Ending balance	13,028,000	13,471,000	13,028,000	13,471,000
Owner Occupied CRE [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	12,756,000	11,948,000	13,813,000	9,928,000
Provision for loan losses	8,260,000	610,000	7,161,000	2,623,000
Recoveries	38,000	14,000	80,000	21,000
Charge-offs	0	0	0	0
Ending balance	21,054,000	12,572,000	21,054,000	12,572,000
Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	13,565,000	9,702,000	11,654,000	9,075,000
Provision for loan losses	2,112,000	167,000	3,925,000	791,000
Recoveries	2,000	12,000	100,000	15,000
Charge-offs	(11,000)	(114,000)	(11,000)	(114,000)
Ending balance	15,668,000	9,767,000	15,668,000	9,767,000
Auto [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	907,000	857,000	810,000	845,000
Provision for loan losses	406,000	99,000	790,000	169,000
Recoveries	89,000	101,000	201,000	233,000
Charge-offs	(329,000)	(228,000)	(728,000)	(418,000)
Ending balance	1,073,000	829,000	1,073,000	829,000
Non-Auto [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	494,000	332,000	391,000	315,000
Provision for loan losses	103,000	87,000	313,000	123,000
Recoveries	24,000	36,000	71,000	81,000
Charge-offs	(108,000)	(122,000)	(262,000)	(186,000)
Ending balance	$ 513,000	$ 333,000	$ 513,000	$ 333,000