Loans - Allowances for Loan Losses and Ending Balances by Portfolio Class and Based on Impairment Method (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses individually evaluated for impairment	$ 29	$ 34
Allowance for loan losses collectively evaluated for impairment	7,091	6,983
Total ending allowance balance	7,120	7,017	$ 6,287	$ 5,907
Loans individually evaluated for impairment	5,908	6,059
Loans collectively evaluated for impairment	548,961	545,074
Total ending loans balance	554,869	551,133
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses individually evaluated for impairment	10	16
Allowance for loan losses collectively evaluated for impairment	2,599	2,392
Total ending allowance balance	2,609	2,408	1,997	2,178
Loans individually evaluated for impairment	2,497	2,555
Loans collectively evaluated for impairment	137,467	134,559
Total ending loans balance	139,964	137,114
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses individually evaluated for impairment	18	17
Allowance for loan losses collectively evaluated for impairment	2,282	2,136
Total ending allowance balance	2,300	2,153	1,808	1,791
Loans individually evaluated for impairment	2,577	2,637
Loans collectively evaluated for impairment	189,810	194,111
Total ending loans balance	192,387	196,748
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses individually evaluated for impairment	1	1
Allowance for loan losses collectively evaluated for impairment	1,346	1,151
Total ending allowance balance	1,347	1,152	1,222	1,245
Loans individually evaluated for impairment	834	853
Loans collectively evaluated for impairment	176,570	173,406
Total ending loans balance	177,404	174,259
Construction & Land Development [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses collectively evaluated for impairment	255	203
Total ending allowance balance	255	203	170	258
Loans collectively evaluated for impairment	26,516	23,960
Total ending loans balance	26,516	23,960
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses collectively evaluated for impairment	518	481
Total ending allowance balance	518	481	325	306
Loans individually evaluated for impairment		14
Loans collectively evaluated for impairment	18,598	19,038
Total ending loans balance	18,598	19,052
Unallocated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses collectively evaluated for impairment	91	620
Total ending allowance balance	$ 91	$ 620	$ 765	$ 129

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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The balance of financing receivables that were individually 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 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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