Loans Held for Investment and Allowance for Loan Losses - Schedule of Allowance for Loan Losses by Portfolio Segment (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2021
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for credit losses	$ 18,298		$ 14,541	$ 15,455
Loans collectively evaluated for credit losses	71,416		61,293	58,653
Total allowance for loan losses	89,714	$ 86,541	75,834	74,108	$ 71,932	$ 63,465
C&I [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for credit losses	6,676		8,398	8,439
Loans collectively evaluated for credit losses	9,131		7,731	8,000
Total allowance for loan losses	15,807	16,530	16,129	16,439	18,589	12,280
Municipal [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for credit losses	185		1,026	1,319
Total allowance for loan losses	185	187	1,026	1,319	1,352	348
Construction & Development [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for credit losses	2,026		305	591
Loans collectively evaluated for credit losses	26,250		26,138	25,108
Total allowance for loan losses	28,276	28,966	26,443	25,699	21,085	17,627
Farm [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for credit losses	1,203		36	41
Loans collectively evaluated for credit losses	1,732		1,921	1,114
Total allowance for loan losses	2,935	2,804	1,957	1,155	1,006	663
Non-Owner Occupied CRE [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for credit losses	3,554		2,357	2,329
Loans collectively evaluated for credit losses	12,263		6,718	5,866
Total allowance for loan losses	15,817	13,471	9,075	8,195	8,410	10,722
Owner Occupied CRE [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for credit losses	2,035		1,600	2,061
Loans collectively evaluated for credit losses	11,491		8,328	8,025
Total allowance for loan losses	13,526	12,572	9,928	10,086	10,740	10,828
Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for credit losses	2,146		1,444	1,640
Loans collectively evaluated for credit losses	8,652		7,631	7,314
Total allowance for loan losses	10,798	9,767	9,075	8,954	8,304	8,133
Auto [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for credit losses	4		2	3
Loans collectively evaluated for credit losses	858		843	909
Total allowance for loan losses	862	829	845	912	912	896
Non-Auto [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for credit losses	2		1	1
Loans collectively evaluated for credit losses	350		314	355
Total allowance for loan losses	352	333	315	356	372	371
Agriculture [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for credit losses	652		398	350
Loans collectively evaluated for credit losses	504		643	643
Total allowance for loan losses	$ 1,156	$ 1,082	$ 1,041	$ 993	$ 1,162	$ 1,597