Loans - Distribution of Fixed Rate Loans and Variable Rate Loans by Major Loan Category (Detail) $ in Thousands	Jun. 30, 2021 USD ($)
Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Distribution of fixed rate loans by major loan category, Fixed Rate	$ 136,798
Distribution of variable rate loans by major loan category, Variable Rate	57,917
Agricultural Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Distribution of fixed rate loans by major loan category, Fixed Rate	112,034
Distribution of variable rate loans by major loan category, Variable Rate	77,708
Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Distribution of fixed rate loans by major loan category, Fixed Rate	86,550
Distribution of variable rate loans by major loan category, Variable Rate	14,206
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Distribution of fixed rate loans by major loan category, Fixed Rate	553,391
Distribution of variable rate loans by major loan category, Variable Rate	137,731
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Distribution of fixed rate loans by major loan category, Fixed Rate	183,955
Distribution of variable rate loans by major loan category, Variable Rate	32,654
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Distribution of fixed rate loans by major loan category, Fixed Rate	52,421
Distribution of variable rate loans by major loan category, Variable Rate	4,006
Other Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Distribution of fixed rate loans by major loan category, Fixed Rate	13,547
Distribution of variable rate loans by major loan category, Variable Rate	$ 2