Loans and Allowance for Credit Losses - Categories of Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accounts Notes And Loans Receivable [Line Items]
Total loans	$ 3,500,816	$ 3,332,901
Allowance for credit losses	(43,267)	(43,520)	$ (45,847)	$ (48,365)
Net loans	3,457,549	3,289,381
Commercial Real Estate [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans	1,830,514	1,759,855
Allowance for credit losses	(14,948)	(13,476)	(16,731)	(22,478)
Commercial and Industrial [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans	658,865	598,327
Allowance for credit losses	(14,005)	(17,954)	(14,951)	(12,248)
Residential Real Estate [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans	566,766	556,328
Allowance for credit losses	(8,553)	(7,784)	(8,608)	(5,560)
Agricultural Real Estate [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans	267,248	196,114
Allowance for credit losses	(3,504)	(1,718)	(819)	(2,235)
Consumer [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans	90,084	103,690
Allowance for credit losses	(1,818)	(1,593)	(2,281)	(2,088)
Agricultural [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans	87,339	118,587
Allowance for credit losses	$ (439)	$ (995)	$ (2,457)	$ (3,756)