Loans - Recorded Investment for Past Due and Non-accruing Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	$ 2,387	$ 5,021
90 Days or More Past Due and Still Accruing	111	213
Nonaccruals	5,206	6,496
Total Past Due and Nonaccruals	7,704	11,730
Current	894,641	754,566
Total Loans	902,345	766,296
Construction, land and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	552	261
Nonaccruals	740	1,237
Total Past Due and Nonaccruals	1,292	1,498
Current	107,475	64,544
Total Loans	108,767	66,042
Farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
90 Days or More Past Due and Still Accruing		48
Total Past Due and Nonaccruals		48
Current	708	875
Total Loans	708	923
Commercial mortgages (non-owner occupied)
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	50	449
Nonaccruals	996
Total Past Due and Nonaccruals	1,046	449
Current	179,028	146,308
Total Loans	180,074	146,757
Commercial mortgages (owner occupied)
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due		573
90 Days or More Past Due and Still Accruing	56
Nonaccruals	1,064	1,752
Total Past Due and Nonaccruals	1,120	2,325
Current	86,121	77,727
Total Loans	87,241	80,052
Residential first mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	1,341	2,670
90 Days or More Past Due and Still Accruing	55	141
Nonaccruals	1,361	1,942
Total Past Due and Nonaccruals	2,757	4,753
Current	296,137	264,612
Total Loans	298,894	269,365
Residential revolving and junior mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	115	449
90 Days or More Past Due and Still Accruing		20
Nonaccruals	782	1,338
Total Past Due and Nonaccruals	897	1,807
Current	37,416	44,691
Total Loans	38,313	46,498
Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due		331
Nonaccruals	48	92
Total Past Due and Nonaccruals	48	423
Current	164,560	113,670
Total Loans	164,608	114,093
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	329	288
90 Days or More Past Due and Still Accruing		4
Nonaccruals	215	135
Total Past Due and Nonaccruals	544	427
Current	23,196	42,139
Total Loans	$ 23,740	$ 42,566