Loans - Summary of Information Regarding the Credit Quality Indicators for Residential Real Estate and Consumer Loans (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	$ 304,669	$ 312,370
Credit Quality [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	89,823	97,793
Credit Quality [Member] | Residential First Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	58,493	65,450
Credit Quality [Member] | Residential Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	1,793	2,041
Credit Quality [Member] | Consumer Home Equity and Lines of Credit [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	29,005	26,691
Credit Quality [Member] | Consumer Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	532	611
Performing [Member] | Credit Quality [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	88,202	95,960
Performing [Member] | Credit Quality [Member] | Residential First Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	57,012	63,760
Performing [Member] | Credit Quality [Member] | Residential Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	1,793	2,041
Performing [Member] | Credit Quality [Member] | Consumer Home Equity and Lines of Credit [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	28,865	29,548
Performing [Member] | Credit Quality [Member] | Consumer Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	532	611
Non Performing [Member] | Credit Quality [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	1,621	1,833
Non Performing [Member] | Credit Quality [Member] | Residential First Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	1,481	1,690
Non Performing [Member] | Credit Quality [Member] | Consumer Home Equity and Lines of Credit [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	$ 140	$ 143