Loans - Contractual Maturity Schedule by Major Category of Loans Excluding Fair Value Adjustments (Detail) $ in Thousands	Dec. 31, 2023 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	$ 2,586,216
Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	525,902
Agricultural Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	224,416
Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	132,593
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	1,337,919
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	255,438
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	79,806
Other Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	30,142
Major Category Of Receivables Due Within One Year [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	287,725
Major Category Of Receivables Due Within One Year [Member] | Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	12,307
Major Category Of Receivables Due Within One Year [Member] | Agricultural Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	546
Major Category Of Receivables Due Within One Year [Member] | Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	62,926
Major Category Of Receivables Due Within One Year [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	109,232
Major Category Of Receivables Due Within One Year [Member] | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	97,823
Major Category Of Receivables Due Within One Year [Member] | Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	2,036
Major Category Of Receivables Due Within One Year [Member] | Other Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	2,855
Major Category Of Receivables Due Within One Year to Five Years [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	632,515
Major Category Of Receivables Due Within One Year to Five Years [Member] | Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	33,817
Major Category Of Receivables Due Within One Year to Five Years [Member] | Agricultural Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	6,149
Major Category Of Receivables Due Within One Year to Five Years [Member] | Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	47,053
Major Category Of Receivables Due Within One Year to Five Years [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	382,123
Major Category Of Receivables Due Within One Year to Five Years [Member] | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	103,806
Major Category Of Receivables Due Within One Year to Five Years [Member] | Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	58,115
Major Category Of Receivables Due Within One Year to Five Years [Member] | Other Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	1,452
Major Category Of Receivables Due After Five Years Within Fifteen Years [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	947,627
Major Category Of Receivables Due After Five Years Within Fifteen Years [Member] | Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	157,139
Major Category Of Receivables Due After Five Years Within Fifteen Years [Member] | Agricultural Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	63,073
Major Category Of Receivables Due After Five Years Within Fifteen Years [Member] | Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	19,184
Major Category Of Receivables Due After Five Years Within Fifteen Years [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	619,438
Major Category Of Receivables Due After Five Years Within Fifteen Years [Member] | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	52,981
Major Category Of Receivables Due After Five Years Within Fifteen Years [Member] | Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	19,561
Major Category Of Receivables Due After Five Years Within Fifteen Years [Member] | Other Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	16,251
Major Category Of Receivables After Fifteen Years [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	718,349
Major Category Of Receivables After Fifteen Years [Member] | Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	322,639
Major Category Of Receivables After Fifteen Years [Member] | Agricultural Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	154,648
Major Category Of Receivables After Fifteen Years [Member] | Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	3,430
Major Category Of Receivables After Fifteen Years [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	227,126
Major Category Of Receivables After Fifteen Years [Member] | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	828
Major Category Of Receivables After Fifteen Years [Member] | Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	94
Major Category Of Receivables After Fifteen Years [Member] | Other Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans excluding fair value adjustments	$ 9,584