Loans - Recorded Investment for Past Due and Non-accruing Loans (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	$ 1,810	$ 2,387
90 Days or More Past Due and Still Accruing	156	111
Nonaccrual	4,577	5,206
Total Past Due and Nonaccrual	6,543	7,704
Current	911,124	894,641
Total Loans	917,667	902,345
Construction, land and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	225	552
Nonaccrual	698	740
Total Past Due and Nonaccrual	923	1,292
Current	109,675	108,183
Total Loans	110,598	109,475
Commercial mortgages (non-owner occupied)
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due		50
Nonaccrual	434	996
Total Past Due and Nonaccrual	434	1,046
Current	178,098	179,028
Total Loans	178,532	180,074
Commercial mortgages (owner occupied)
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	144
90 Days or More Past Due and Still Accruing		56
Nonaccrual	238	1,064
Total Past Due and Nonaccrual	382	1,120
Current	82,608	86,121
Total Loans	82,990	87,241
Residential first mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	1,063	1,341
90 Days or More Past Due and Still Accruing	156	55
Nonaccrual	1,984	1,361
Total Past Due and Nonaccrual	3,203	2,757
Current	302,049	296,137
Total Loans	305,252	298,894
Residential revolving and junior mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	99	115
Nonaccrual	936	782
Total Past Due and Nonaccrual	1,035	897
Current	34,840	37,416
Total Loans	35,875	38,313
Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual		48
Total Past Due and Nonaccrual		48
Current	187,531	164,560
Total Loans	187,531	164,608
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	279	329
Nonaccrual	287	215
Total Past Due and Nonaccrual	566	544
Current	16,323	23,196
Total Loans	$ 16,889	$ 23,740