Loans - Schedule of Aging of Past Due and Nonaccrual Loans (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	$ 529,186	$ 508,392
Non-accrual	4,317	6,081
Total past due and non-accrual	5,675	7,908
Total ending loans balance	534,861	516,300
30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	794	1,275
60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	482	111
90 Days Plus Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	82	441
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	141,180	138,908
Non-accrual	721	1,152
Total past due and non-accrual	839	1,365
Total ending loans balance	142,019	140,273
Commercial [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	43	148
Commercial [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	75	65
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	178,927	175,062
Non-accrual	3,052	4,384
Total past due and non-accrual	3,107	4,601
Total ending loans balance	182,034	179,663
Commercial Real Estate [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	55	177
Commercial Real Estate [Member] | 90 Days Plus Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		40
Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	160,667	155,488
Non-accrual	524	488
Total past due and non-accrual	1,517	1,684
Total ending loans balance	162,184	157,172
Residential Real Estate [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	585	757
Residential Real Estate [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	326	38
Residential Real Estate [Member] | 90 Days Plus Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	82	401
Construction & Land Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	30,706	22,886
Total ending loans balance	30,706	22,886
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	17,706	16,048
Non-accrual	20	57
Total past due and non-accrual	212	258
Total ending loans balance	17,918	16,306
Consumer [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	111	193
Consumer [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 81	$ 8