Loans - Recorded Investment in Past Due and Non-accruing Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	$ 2,679	$ 1,906
90 Days or More Past Due and Still Accruing		11
Nonaccruals	5,300	6,433
Total Past Due and Nonaccruals	7,979	8,350
Current	377,030	338,872
Total Gross Loans	385,009	347,222
Construction, Land and Land Development
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due		93
Nonaccruals	623	672
Total Past Due and Nonaccruals	623	765
Current	39,195	41,364
Total Gross Loans	39,818	42,129
Farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	57
Total Past Due and Nonaccruals	57
Current	966	1,030
Total Gross Loans	1,023	1,030
Commercial Mortgages (Non-Owner Occupied)
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due		264
Total Past Due and Nonaccruals		264
Current	35,343	28,822
Total Gross Loans	35,343	29,086
Commercial Mortgages (Owner Occupied)
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	188	133
Nonaccruals	2,270	2,350
Total Past Due and Nonaccruals	2,458	2,483
Current	39,367	41,473
Total Gross Loans	41,825	43,956
Residential First Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	1,546	1,304
Nonaccruals	2,155	2,841
Total Past Due and Nonaccruals	3,701	4,145
Current	190,306	160,260
Total Gross Loans	194,007	164,405
Residential Revolving and Junior Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	480	70
Nonaccruals	160	277
Total Past Due and Nonaccruals	640	347
Current	25,785	26,150
Total Gross Loans	26,425	26,497
Commercial and Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	408	10
Nonaccruals	92	285
Total Past Due and Nonaccruals	500	295
Current	42,524	34,809
Total Gross Loans	43,024	35,104
Consumer and Other Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due		32
90 Days or More Past Due and Still Accruing		11
Nonaccruals		8
Total Past Due and Nonaccruals		51
Current	3,544	4,964
Total Gross Loans	$ 3,544	$ 5,015