Loans and Allowance for Credit Losses - Categories of Loans (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022
Accounts Notes And Loans Receivable [Line Items]
Total loans	$ 3,454,407		$ 3,332,901
Allowance for credit losses	(43,487)	$ (44,449)	(43,520)	$ (44,544)	$ (45,103)	$ (45,847)
Net loans	3,410,920		3,289,381
Commercial Real Estate [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans	1,793,544		1,759,855
Allowance for credit losses	(14,492)	(13,582)	(13,476)	(16,652)	(16,611)	(16,731)
Commercial and Industrial [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans	663,718		598,327
Allowance for credit losses	(16,407)	(17,651)	(17,954)	(15,194)	(15,620)	(14,951)
Residential Real Estate [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans	572,523		556,328
Allowance for credit losses	(8,066)	(8,319)	(7,784)	(8,855)	(8,751)	(8,608)
Agricultural Real Estate [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans	219,226		196,114
Allowance for credit losses	(2,254)	(1,688)	(1,718)	(583)	(586)	(819)
Consumer [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans	101,054		103,690
Allowance for credit losses	(1,746)	(1,597)	(1,593)	(1,971)	(1,988)	(2,281)
Agricultural [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans	104,342		118,587
Allowance for credit losses	$ (522)	$ (1,612)	$ (995)	$ (1,289)	$ (1,547)	$ (2,457)