Loans - Recorded Investment in Past Due and Non-accruing Loans (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	$ 1,005	$ 2,679
90 Days or More Past Due and Still Accruing	0	0
Nonaccruals	5,820	5,300
Total Past Due and Nonaccruals	6,825	7,979
Current	398,027	377,030
Total Gross Loans	404,852	385,009
Construction, Land and Land Development
Accounts, Notes, Loans and Financing Receivable [Line Items]
90 Days or More Past Due and Still Accruing	0	0
Nonaccruals	547	623
Total Past Due and Nonaccruals	547	623
Current	43,572	39,195
Total Gross Loans	44,119	39,818
Farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due		57
90 Days or More Past Due and Still Accruing	0	0
Total Past Due and Nonaccruals		57
Current	994	966
Total Gross Loans	994	1,023
Commercial Mortgages (Non-Owner Occupied)
Accounts, Notes, Loans and Financing Receivable [Line Items]
90 Days or More Past Due and Still Accruing	0	0
Current	35,464	35,343
Total Gross Loans	35,464	35,343
Commercial Mortgages (Owner Occupied)
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due		188
90 Days or More Past Due and Still Accruing	0	0
Nonaccruals	2,148	2,270
Total Past Due and Nonaccruals	2,148	2,458
Current	40,402	39,367
Total Gross Loans	42,550	41,825
Residential First Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	402	1,546
90 Days or More Past Due and Still Accruing	0	0
Nonaccruals	1,975	2,155
Total Past Due and Nonaccruals	2,377	3,701
Current	202,729	190,306
Total Gross Loans	205,106	194,007
Residential Revolving and Junior Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due		480
90 Days or More Past Due and Still Accruing	0	0
Nonaccruals	1,039	160
Total Past Due and Nonaccruals	1,039	640
Current	26,051	25,785
Total Gross Loans	27,090	26,425
Commercial and Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	603	408
90 Days or More Past Due and Still Accruing	0	0
Nonaccruals	111	92
Total Past Due and Nonaccruals	714	500
Current	45,491	42,524
Total Gross Loans	46,205	43,024
Consumer and Other Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
90 Days or More Past Due and Still Accruing	0	0
Current	3,324	3,544
Total Gross Loans	$ 3,324	$ 3,544