Allowance for Loan Losses - Ending Allocation of Allowance for Loan Losses and Loan Balances Outstanding (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Accounts Notes And Loans Receivable [Line Items]
Allowance for loan losses, Individually evaluated for impairment	$ 34	$ 107
Allowance for loan losses, Collectively evaluated for impairment	26,099	24,921
Allowance for loan losses, Total	26,133	25,028	$ 16,948	$ 14,767
Outstanding loan balances, Individually evaluated for impairment	1,521	2,666
Outstanding loan balances, Collectively evaluated for impairment	2,058,380	2,054,448
Outstanding loan balances, Total	2,060,239	2,057,502
Receivables Acquired with Deteriorated Credit Quality [Member]
Accounts Notes And Loans Receivable [Line Items]
Loan balance of loans acquired with credit deterioration	338	388
Commercial and Agriculture [Member]
Accounts Notes And Loans Receivable [Line Items]
Allowance for loan losses, Individually evaluated for impairment		73
Allowance for loan losses, Collectively evaluated for impairment	2,360	2,737
Allowance for loan losses, Total	2,360	2,810	2,400	2,219
Outstanding loan balances, Individually evaluated for impairment		74
Outstanding loan balances, Collectively evaluated for impairment	419,666	409,802
Outstanding loan balances, Total	419,666	409,876
Commercial Real Estate Owner Occupied [Member]
Accounts Notes And Loans Receivable [Line Items]
Allowance for loan losses, Individually evaluated for impairment	5	5
Allowance for loan losses, Collectively evaluated for impairment	4,044	4,052
Allowance for loan losses, Total	4,049	4,057	2,810	2,541
Outstanding loan balances, Individually evaluated for impairment	309	980
Outstanding loan balances, Collectively evaluated for impairment	274,438	277,433
Outstanding loan balances, Total	274,747	278,413
Commercial Real Estate Non Owner Occupied [Member]
Accounts Notes And Loans Receivable [Line Items]
Allowance for loan losses, Collectively evaluated for impairment	13,209	12,451
Allowance for loan losses, Total	13,209	12,451	7,617	6,584
Outstanding loan balances, Individually evaluated for impairment	39	48
Outstanding loan balances, Collectively evaluated for impairment	723,617	705,024
Outstanding loan balances, Total	723,656	705,072
Residential Real Estate [Member]
Accounts Notes And Loans Receivable [Line Items]
Allowance for loan losses, Individually evaluated for impairment	29	29
Allowance for loan losses, Collectively evaluated for impairment	2,480	2,455
Allowance for loan losses, Total	2,509	2,484	1,950	1,582
Outstanding loan balances, Individually evaluated for impairment	568	946
Outstanding loan balances, Collectively evaluated for impairment	430,600	441,254
Outstanding loan balances, Total	431,506	442,588
Residential Real Estate [Member] \| Receivables Acquired with Deteriorated Credit Quality [Member]
Accounts Notes And Loans Receivable [Line Items]
Loan balance of loans acquired with credit deterioration	338	388
Real Estate Construction [Member]
Accounts Notes And Loans Receivable [Line Items]
Allowance for loan losses, Collectively evaluated for impairment	2,902	2,439
Allowance for loan losses, Total	2,902	2,439	1,606	1,250
Outstanding loan balances, Collectively evaluated for impairment	171,121	175,609
Outstanding loan balances, Total	171,121	175,609
Farm Real Estate [Member]
Accounts Notes And Loans Receivable [Line Items]
Allowance for loan losses, Collectively evaluated for impairment	283	338
Allowance for loan losses, Total	283	338	310	344
Outstanding loan balances, Individually evaluated for impairment	605	618
Outstanding loan balances, Collectively evaluated for impairment	27,438	32,484
Outstanding loan balances, Total	28,043	33,102
Consumer and Other [Member]
Accounts Notes And Loans Receivable [Line Items]
Allowance for loan losses, Collectively evaluated for impairment	170	209
Allowance for loan losses, Total	170	209	246	$ 247
Outstanding loan balances, Collectively evaluated for impairment	11,500	12,842
Outstanding loan balances, Total	11,500	12,842
Unallocated [Member]
Accounts Notes And Loans Receivable [Line Items]
Allowance for loan losses, Collectively evaluated for impairment	651	240
Allowance for loan losses, Total	$ 651	$ 240	$ 9

Financing receivable acquired with credit deterioration.

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Amount of allowance for credit loss on accounts receivable.

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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