Loans - Schedule of Aging of Past Due and Nonaccrual Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	$ 502,693	$ 471,722
Nonaccrual	4,677	1,449
Total Past Due and Nonaccrual	6,236	3,246
Total ending loans balance	508,929	474,968
30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,189	1,423
60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	117	139
90 Days Plus Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	253	235
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	136,544	133,630
Nonaccrual	743	425
Total Past Due and Nonaccrual	915	638
Total ending loans balance	137,459	134,268
Commercial [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	28	151
Commercial [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		62
Commercial [Member] | 90 Days Plus Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	144
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	173,989	158,504
Nonaccrual	3,399	497
Total Past Due and Nonaccrual	3,599	971
Total ending loans balance	177,588	159,475
Commercial Real Estate [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	160	435
Commercial Real Estate [Member] | 90 Days Plus Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	40	39
Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	151,684	142,926
Nonaccrual	507	490
Total Past Due and Nonaccrual	1,597	1,563
Total ending loans balance	153,281	144,489
Residential Real Estate [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	914	816
Residential Real Estate [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	108	61
Residential Real Estate [Member] | 90 Days Plus Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	68	196
Construction & Land Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	23,915	23,428
Total ending loans balance	23,915	23,428
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	16,561	13,234
Nonaccrual	28	37
Total Past Due and Nonaccrual	125	74
Total ending loans balance	16,686	13,308
Consumer [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	87	21
Consumer [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	9	$ 16
Consumer [Member] | 90 Days Plus Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 1