Loans Held for Investment and Allowance for Loan Losses - Schedule of Allowance for Loan Losses by Portfolio Segment (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for credit losses	$ 18,744	$ 17,870	$ 18,573
Loans collectively evaluated for credit losses	48,169	45,595	44,401
Total allowance for loan losses	66,913	63,465	62,974	$ 66,534
C&I [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for credit losses	7,793	6,627	3,881
Loans collectively evaluated for credit losses	7,944	5,653	8,442
Total allowance for loan losses	15,737	12,280	12,323	13,609
Municipal [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for credit losses	0		1,536
Loans collectively evaluated for credit losses	1,418	348	655
Total allowance for loan losses	1,418	348	2,191	1,552
Construction & Development [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for credit losses	1,490	225	880
Loans collectively evaluated for credit losses	16,397	17,402	12,366
Total allowance for loan losses	17,887	17,627	13,246	13,512
Farm [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for credit losses	0	2	671
Loans collectively evaluated for credit losses	873	661	552
Total allowance for loan losses	873	663	1,223	1,876
Non-Owner Occupied CRE [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for credit losses	3,016	4,059	3,335
Loans collectively evaluated for credit losses	5,483	6,663	6,157
Total allowance for loan losses	8,499	10,722	9,492	8,391
Owner Occupied CRE [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for credit losses	3,245	3,481	3,599
Loans collectively evaluated for credit losses	8,291	7,347	6,279
Total allowance for loan losses	11,536	10,828	9,878	12,347
Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for credit losses	1,974	2,026	2,874
Loans collectively evaluated for credit losses	5,855	6,107	8,315
Total allowance for loan losses	7,829	8,133	11,189	12,601
Auto [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for credit losses		4	5
Loans collectively evaluated for credit losses	866	892	1,063
Total allowance for loan losses	869	896	1,068	1,020
Non-Auto [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for credit losses	1	1	2
Loans collectively evaluated for credit losses	353	370	377
Total allowance for loan losses	354	371	379	371
Agriculture [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for credit losses	1,222	1,445	1,790
Loans collectively evaluated for credit losses	689	152	195
Total allowance for loan losses	$ 1,911	$ 1,597	$ 1,985	$ 1,255