Allowance for Loans Losses - Summary of loans and leases receivable method of impairment evaluation (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Loans and Leases Receivable Disclosure [Line Items]
Gross loans	$ 461,516	$ 415,587
Less: Unearned income	(638)	(719)
Total	460,878	414,868
Individually Evaluated for Impairment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Gross loans	1,684	1,946
Total	1,684	1,946
Collectively Evaluated for Impairment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Gross loans	459,832	413,641
Less: Unearned income	(638)	(719)
Total	459,194	412,922
Commercial and industrial [Member]
Loans and Leases Receivable Disclosure [Line Items]
Gross loans	50,826	49,076
Commercial and industrial [Member] \| Individually Evaluated for Impairment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Gross loans	291
Commercial and industrial [Member] \| Collectively Evaluated for Impairment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Gross loans	50,535	49,076
Agricultural [Member]
Loans and Leases Receivable Disclosure [Line Items]
Gross loans	175	216
Agricultural [Member] \| Collectively Evaluated for Impairment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Gross loans	175	216
Construction, commercial [Member] \| Real Estate [Member]
Loans and Leases Receivable Disclosure [Line Items]
Gross loans	19,876	14,666
Construction, commercial [Member] \| Collectively Evaluated for Impairment [Member] \| Real Estate [Member]
Loans and Leases Receivable Disclosure [Line Items]
Gross loans	19,876	14,666
Construction, residential [Member] \| Real Estate [Member]
Loans and Leases Receivable Disclosure [Line Items]
Gross loans	16,364	15,102
Construction, residential [Member] \| Collectively Evaluated for Impairment [Member] \| Real Estate [Member]
Loans and Leases Receivable Disclosure [Line Items]
Gross loans	16,364	15,102
Mortgage, commercial [Member] \| Real Estate [Member]
Loans and Leases Receivable Disclosure [Line Items]
Gross loans	167,223	150,513
Mortgage, commercial [Member] \| Individually Evaluated for Impairment [Member] \| Real Estate [Member]
Loans and Leases Receivable Disclosure [Line Items]
Gross loans	735	1,258
Mortgage, commercial [Member] \| Collectively Evaluated for Impairment [Member] \| Real Estate [Member]
Loans and Leases Receivable Disclosure [Line Items]
Gross loans	166,488	149,255
Mortgage, residential [Member] \| Real Estate [Member]
Loans and Leases Receivable Disclosure [Line Items]
Gross loans	165,865	149,856
Mortgage, residential [Member] \| Individually Evaluated for Impairment [Member] \| Real Estate [Member]
Loans and Leases Receivable Disclosure [Line Items]
Gross loans	658	688
Mortgage, residential [Member] \| Collectively Evaluated for Impairment [Member] \| Real Estate [Member]
Loans and Leases Receivable Disclosure [Line Items]
Gross loans	165,207	149,168
Mortgage, farmland [Member] \| Real Estate [Member]
Loans and Leases Receivable Disclosure [Line Items]
Gross loans	3,754	4,179
Mortgage, farmland [Member] \| Collectively Evaluated for Impairment [Member] \| Real Estate [Member]
Loans and Leases Receivable Disclosure [Line Items]
Gross loans	3,754	4,179
Consumer installment loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Gross loans	37,433	31,979
Consumer installment loans [Member] \| Collectively Evaluated for Impairment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Gross loans	$ 37,433	$ 31,979

Amount of deferred interest and fee income, unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of acquired loans. Excludes amounts for loans and leases covered under loss sharing agreements.

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-SubTopic 210
-Section S99
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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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