Allowance for Loan Losses - Past Due Information of Loan Portfolio by Class (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Financing Receivable, Impaired [Line Items]
Total Past Due Loans	$ 2,685	$ 2,707
Current Loans	341,857	317,425
Total Loans	344,542	320,132
Accruing Loans 90 or More Days Past Due	0	0
Commercial Loan [Member]
Financing Receivable, Impaired [Line Items]
Total Past Due Loans	13	80
Current Loans	54,865	52,231
Total Loans	54,878	52,311
Accruing Loans 90 or More Days Past Due	0	0
Consumer Loans [Member]
Financing Receivable, Impaired [Line Items]
Total Past Due Loans	98	39
Current Loans	9,617	8,943
Total Loans	9,715	8,982
Accruing Loans 90 or More Days Past Due	0	0
Real Estate - Commercial [Member]
Financing Receivable, Impaired [Line Items]
Total Past Due Loans	484	74
Current Loans	109,014	101,124
Total Loans	109,498	101,198
Accruing Loans 90 or More Days Past Due	0	0
Other Real Estate Construction [Member]
Financing Receivable, Impaired [Line Items]
Total Past Due Loans	191	305
Current Loans	27,028	17,387
Total Loans	27,219	17,692
Accruing Loans 90 or More Days Past Due	0	0
Real Estate 1 - 4 Family Construction [Member]
Financing Receivable, Impaired [Line Items]
Total Past Due Loans	0
Current Loans	4,794
Total Loans	4,794	5,629
Accruing Loans 90 or More Days Past Due	0
Real Estate - Residential [Member]
Financing Receivable, Impaired [Line Items]
Total Past Due Loans	1,802	2,121
Current Loans	83,501	81,298
Total Loans	85,303	83,419
Accruing Loans 90 or More Days Past Due	0	0
Home Equity [Member]
Financing Receivable, Impaired [Line Items]
Total Past Due Loans	97	88
Current Loans	51,306	49,332
Total Loans	51,403	49,420
Accruing Loans 90 or More Days Past Due	0	0
Other Loans [Member]
Financing Receivable, Impaired [Line Items]
Total Past Due Loans		0
Current Loans	1,732	1,481
Total Loans	1,732	1,481
Accruing Loans 90 or More Days Past Due	0	0
Real Estate Construction [Member]
Financing Receivable, Impaired [Line Items]
Total Past Due Loans		0
Current Loans		5,629
Total Loans		5,629
Accruing Loans 90 or More Days Past Due		0
Loans 30-89 Days Past Due [Member]
Financing Receivable, Impaired [Line Items]
Total Past Due Loans	1,501	1,924
Loans 30-89 Days Past Due [Member] | Commercial Loan [Member]
Financing Receivable, Impaired [Line Items]
Total Past Due Loans	13	46
Loans 30-89 Days Past Due [Member] | Consumer Loans [Member]
Financing Receivable, Impaired [Line Items]
Total Past Due Loans	98	39
Loans 30-89 Days Past Due [Member] | Real Estate - Commercial [Member]
Financing Receivable, Impaired [Line Items]
Total Past Due Loans	89	74
Loans 30-89 Days Past Due [Member] | Other Real Estate Construction [Member]
Financing Receivable, Impaired [Line Items]
Total Past Due Loans		110
Loans 30-89 Days Past Due [Member] | Real Estate - Residential [Member]
Financing Receivable, Impaired [Line Items]
Total Past Due Loans	1,226	1,580
Loans 30-89 Days Past Due [Member] | Home Equity [Member]
Financing Receivable, Impaired [Line Items]
Total Past Due Loans	75	75
Loans 90 Days or More Past Due [Member]
Financing Receivable, Impaired [Line Items]
Total Past Due Loans	1,184	783
Loans 90 Days or More Past Due [Member] | Commercial Loan [Member]
Financing Receivable, Impaired [Line Items]
Total Past Due Loans		34
Loans 90 Days or More Past Due [Member] | Real Estate - Commercial [Member]
Financing Receivable, Impaired [Line Items]
Total Past Due Loans	395
Loans 90 Days or More Past Due [Member] | Other Real Estate Construction [Member]
Financing Receivable, Impaired [Line Items]
Total Past Due Loans	191	195
Loans 90 Days or More Past Due [Member] | Real Estate - Residential [Member]
Financing Receivable, Impaired [Line Items]
Total Past Due Loans	576	541
Loans 90 Days or More Past Due [Member] | Home Equity [Member]
Financing Receivable, Impaired [Line Items]
Total Past Due Loans	$ 22	$ 13