Loans - Schedule of Allowances for Loan Losses by Portfolio Segment (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 7,120	$ 6,287	$ 7,017	$ 5,907
Provision for loan losses	717	285	895	570
Charge-offs	(16)	(54)	(103)	(124)
Recoveries	14	19	26	184
Net (charge-offs) recoveries	(2)	(35)	(77)	60
Ending balance	7,835	6,537	7,835	6,537
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	2,609	1,997	2,408	2,178
Provision for loan losses	(343)	277	(131)	(62)
Charge-offs	(4)	(11)	(19)	(16)
Recoveries	4	4	8	167
Net (charge-offs) recoveries		(7)	(11)	151
Ending balance	2,266	2,267	2,266	2,267
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	2,300	1,808	2,153	1,791
Provision for loan losses	480	138	627	155
Recoveries	1		1
Net (charge-offs) recoveries	1		1
Ending balance	2,781	1,946	2,781	1,946
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	1,347	1,222	1,152	1,245
Provision for loan losses	237	5	446	(19)
Charge-offs			(15)
Recoveries	1	2	2	3
Net (charge-offs) recoveries	1	2	(13)	3
Ending balance	1,585	1,229	1,585	1,229
Construction & Land Development [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	255	170	203	258
Provision for loan losses	82	(66)	134	(154)
Ending balance	337	104	337	104
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	518	325	481	306
Provision for loan losses	2	46	89	129
Charge-offs	(12)	(43)	(69)	(108)
Recoveries	8	13	15	14
Net (charge-offs) recoveries	(4)	(30)	(54)	(94)
Ending balance	516	341	516	341
Unallocated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	91	765	620	129
Provision for loan losses	259	(115)	(270)	521
Ending balance	$ 350	$ 650	$ 350	$ 650

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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Amount of other addition (reduction) in allowance reserve for credit loss.

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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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 of expense related to estimated loss from loan and lease transactions.

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