Allowance for Loan Losses - Loans Evaluated for Impairment Individually and Collectively by Loan Type (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans individually evaluated for impairment	$ 1,039	$ 1,157
Loans collectively evaluated for impairment	6,523	6,745
Purchased credit-impaired loans	0	0
Total allowance on loan losses	7,562	7,902	$ 7,770
Loans individually evaluated for impairment	6,069	7,606
Loans collectively evaluated for impairment	913,564	889,416
Purchased credit-impaired loans	4,870	5,323
Total Loans	924,503	902,345
Mortgage Loans on Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans individually evaluated for impairment	878	1,036
Loans collectively evaluated for impairment	4,494	3,931
Purchased credit-impaired loans	0	0
Total allowance on loan losses	5,372	4,967	3,864
Loans individually evaluated for impairment	5,502	7,485
Loans collectively evaluated for impairment	720,458	701,235
Purchased credit-impaired loans	4,828	5,277
Total Loans	730,788	713,997
Commercial and Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans individually evaluated for impairment	49
Loans collectively evaluated for impairment	1,522	1,374
Purchased credit-impaired loans	0	0
Total allowance on loan losses	1,571	1,374	878
Loans individually evaluated for impairment	455
Loans collectively evaluated for impairment	181,275	164,608
Total Loans	181,730	164,608
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans individually evaluated for impairment	112	121
Loans collectively evaluated for impairment	507	1,440
Purchased credit-impaired loans	0	0
Total allowance on loan losses	619	1,561	$ 3,028
Loans individually evaluated for impairment	112	121
Loans collectively evaluated for impairment	11,831	23,573
Purchased credit-impaired loans	42	46
Total Loans	$ 11,985	$ 23,740