Allowance for Loan Losses - Summary of Nonaccrual Loans Excluding Purchased Credit-Impaired (PCI) Loans (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Recorded Investment [Line Items]
Total, Non-Accrual Status	$ 5,574	$ 5,599
Commercial and Agriculture [Member]
Financing Receivable, Recorded Investment [Line Items]
Total, Non-Accrual Status	160	173
Commercial Real Estate Owner Occupied [Member]
Financing Receivable, Recorded Investment [Line Items]
Total, Non-Accrual Status	855	938
Commercial Real Estate Non Owner Occupied [Member]
Financing Receivable, Recorded Investment [Line Items]
Total, Non-Accrual Status	8	8
Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total, Non-Accrual Status	4,256	4,183
Real Estate Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Total, Non-Accrual Status	9	9
Farm Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total, Non-Accrual Status	274	284
Consumer and Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total, Non-Accrual Status	$ 12	$ 4