Loans and Allowance for Credit Losses - Schedule of Allowance for Credit Losses on Off-Balance Sheet Credit Exposures (Detail) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accounts Notes And Loans Receivable [Line Items]
Loans, allowance for credit losses	$ 43,267	$ 43,520	$ 45,847	$ 48,365
Commercial Real Estate [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans, allowance for credit losses	14,948	13,476	16,731	22,478
Commercial and Industrial [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans, allowance for credit losses	14,005	17,954	14,951	12,248
Residential Real Estate [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans, allowance for credit losses	8,553	7,784	8,608	5,560
Agricultural Real Estate [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans, allowance for credit losses	3,504	1,718	819	2,235
Agricultural [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans, allowance for credit losses	439	995	2,457	3,756
Consumer [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans, allowance for credit losses	1,818	1,593	$ 2,281	$ 2,088
SEC Schedule, 12-09, Allowance, Credit Loss [Member] | Off Balance Sheet Credit Loss Liability [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans, allowance for credit losses	1,442	1,625
SEC Schedule, 12-09, Allowance, Credit Loss [Member] | Commercial Real Estate [Member] | Off Balance Sheet Credit Loss Liability [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans, allowance for credit losses	188	285
SEC Schedule, 12-09, Allowance, Credit Loss [Member] | Commercial and Industrial [Member] | Off Balance Sheet Credit Loss Liability [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans, allowance for credit losses	1,170	1,053
SEC Schedule, 12-09, Allowance, Credit Loss [Member] | Residential Real Estate [Member] | Off Balance Sheet Credit Loss Liability [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans, allowance for credit losses	69	35
SEC Schedule, 12-09, Allowance, Credit Loss [Member] | Agricultural Real Estate [Member] | Off Balance Sheet Credit Loss Liability [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans, allowance for credit losses	1	2
SEC Schedule, 12-09, Allowance, Credit Loss [Member] | Agricultural [Member] | Off Balance Sheet Credit Loss Liability [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans, allowance for credit losses	12	3
SEC Schedule, 12-09, Allowance, Credit Loss [Member] | Consumer [Member] | Off Balance Sheet Credit Loss Liability [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans, allowance for credit losses	$ 2	$ 247