Loans - Summary of Information Regarding the Credit Quality Indicators for Residential Real Estate and Consumer Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	$ 325,992	$ 331,598
Credit Quality [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	101,209	94,631
Credit Quality [Member] | Residential First Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	80,661	68,968
Credit Quality [Member] | Residential Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	3,388	2,954
Credit Quality [Member] | Consumer Home Equity and Lines of Credit [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	17,032	22,348
Credit Quality [Member] | Consumer Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	128	361
Performing [Member] | Credit Quality [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	100,192	93,344
Performing [Member] | Credit Quality [Member] | Residential First Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	79,722	67,817
Performing [Member] | Credit Quality [Member] | Residential Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	3,388	2,954
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	16,954	22,212
Performing [Member] | Credit Quality [Member] | Consumer Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	128	361
Non Performing [Member] | Credit Quality [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	1,017	1,287
Non Performing [Member] | Credit Quality [Member] | Residential First Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	939	1,151
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	$ 78	$ 136