Loans - Summary of Information Regarding the Credit Quality Indicators for Residential Real Estate and Consumer Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	$ 312,370	$ 372,589
Credit Quality [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	97,793	148,249
Credit Quality [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	95,960	147,013
Credit Quality [Member] | Non Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	1,833	1,236
Credit Quality [Member] | Residential First Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	65,450	108,084
Credit Quality [Member] | Residential First Mortgages [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	63,760	107,018
Credit Quality [Member] | Residential First Mortgages [Member] | Non Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	1,690	1,066
Credit Quality [Member] | Residential Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	2,041	2,097
Credit Quality [Member] | Residential Construction [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	2,041	2,097
Credit Quality [Member] | Consumer Home Equity and Lines of Credit [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	29,691	36,154
Credit Quality [Member] | Consumer Home Equity and Lines of Credit [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	29,548	35,984
Credit Quality [Member] | Consumer Home Equity and Lines of Credit [Member] | Non Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	143	170
Credit Quality [Member] | Consumer Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	611	1,914
Credit Quality [Member] | Consumer Other [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	$ 611	$ 1,914