Commitments and Contingencies - Summary of Financial Instruments Outstanding Contract Amounts Represent Credit Risk (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Commitments to Originate Loans [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Financial instruments with off-balance-sheet risk	$ 85,463	$ 107,889
Unused Lines and Letters of Credit [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Financial instruments with off-balance-sheet risk	75,823	79,012
Unadvanced Funds on Construction Loans [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Financial instruments with off-balance-sheet risk	13,895	13,879
Overdraft Lines of Credit [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Financial instruments with off-balance-sheet risk	$ 7,787	$ 7,967