Loans - Schedule of Analysis of Past due Loans (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Past Due	$ 951	$ 1,239
Current Loans	329,043	330,359
Total Loans	329,994	331,598
Commercial Real Estate [Member]
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Past Due		241
Current Loans	184,400	189,050
Total Loans	184,400	189,291
Commercial Land Development [Member]
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Current Loans	1,475	1,492
Total Loans	1,475	1,492
Commercial Other [Member]
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Past Due		33
Current Loans	43,915	46,151
Total Loans	43,915	46,184
Residential Real Estate First Mortgages [Member]
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Past Due	918	821
Current Loans	77,016	68,147
Total Loans	77,934	68,968
Residential Real Estate Construction [Member]
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Current Loans	2,042	2,954
Total Loans	2,042	2,954
Consumer Home Equity and Lines of Credit [Member]
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Past Due	33	144
Current Loans	19,922	22,204
Total Loans	19,955	22,348
Consumer Other [Member]
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Current Loans	273	361
Total Loans	273	361
Loans Past Due 30-89 Days [Member]
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Past Due	946	1,079
Loans Past Due 30-89 Days [Member] | Commercial Real Estate [Member]
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Past Due		241
Loans Past Due 30-89 Days [Member] | Commercial Other [Member]
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Past Due		33
Loans Past Due 30-89 Days [Member] | Residential Real Estate First Mortgages [Member]
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Past Due	918	684
Loans Past Due 30-89 Days [Member] | Consumer Home Equity and Lines of Credit [Member]
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Past Due	28	121
Loans Past Due 90+ Days [Member]
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Past Due	5	160
Loans Past Due 90+ Days [Member] | Residential Real Estate First Mortgages [Member]
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Past Due		137
Loans Past Due 90+ Days [Member] | Consumer Home Equity and Lines of Credit [Member]
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Past Due	$ 5	$ 23