Loans - Distribution of Fixed Rate Loans and Variable Rate Loans by Portfolio Segment (Detail) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Distribution of fixed rate loans by major loan category, Fixed Rate	$ 291,720	$ 305,062
Distribution of variable rate loans by major loan category, Variable Rate	231,663	215,052
Agricultural Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Distribution of fixed rate loans by major loan category, Fixed Rate	113,451	118,808
Distribution of variable rate loans by major loan category, Variable Rate	102,447	97,593
Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Distribution of fixed rate loans by major loan category, Fixed Rate	50,487	54,099
Distribution of variable rate loans by major loan category, Variable Rate	103,120	97,981
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Distribution of fixed rate loans by major loan category, Fixed Rate	890,046	934,197
Distribution of variable rate loans by major loan category, Variable Rate	435,652	376,614
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Distribution of fixed rate loans by major loan category, Fixed Rate	123,414	148,542
Distribution of variable rate loans by major loan category, Variable Rate	154,840	126,610
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Distribution of fixed rate loans by major loan category, Fixed Rate	60,084	62,977
Distribution of variable rate loans by major loan category, Variable Rate	31	32
Other Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Distribution of fixed rate loans by major loan category, Fixed Rate	15,427	15,270
Distribution of variable rate loans by major loan category, Variable Rate	$ 9,558	$ 9,708