Loans - Summary of Allowance for Loan and Lease Losses for Loans Evaluated Individually and Collectively for Impairment (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Loans and Leases Receivable Disclosure [Line Items]
Individually evaluated for impairment	$ 10,461	$ 11,005
Collectively evaluated for impairment	319,533	320,593
Total loans	329,994	331,598
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	2,699	2,703
Total allowance for loan losses	2,699	2,703	$ 2,008	$ 2,000
Commercial [Member]
Loans and Leases Receivable Disclosure [Line Items]
Individually evaluated for impairment	9,815	10,573
Collectively evaluated for impairment	219,975	226,394
Total loans	229,790	236,967
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	1,614	1,609
Total allowance for loan losses	1,614	1,609	1,241	1,235
Residential [Member]
Loans and Leases Receivable Disclosure [Line Items]
Individually evaluated for impairment	625	411
Collectively evaluated for impairment	79,351	71,511
Total loans	79,976	71,922
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	745	745
Total allowance for loan losses	745	745	573	573
Consumer [Member]
Loans and Leases Receivable Disclosure [Line Items]
Individually evaluated for impairment	21	21
Collectively evaluated for impairment	20,207	22,688
Total loans	20,228	22,709
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	340	349
Total allowance for loan losses	$ 340	$ 349	$ 194	$ 192

The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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The balance of financing receivables that were collectively evaluated for impairment.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount, after allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement.

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