Commitments and Contingencies - Summary of Financial Instrument Liabilities Represent Off-Balance Sheet Credit Risk (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Loss Contingencies [Line Items]
Off-balance-sheet, credit risk	$ 161,181	$ 107,571
Commitments To Originate Loans
Loss Contingencies [Line Items]
Off-balance-sheet, credit risk	54,505	24,658
Unadvanced Funds On Lines Of Credit
Loss Contingencies [Line Items]
Off-balance-sheet, credit risk	52,812	45,548
Unadvanced Funds on Construction Loans
Loss Contingencies [Line Items]
Off-balance-sheet, credit risk	53,851	37,352
Letters of Credit
Loss Contingencies [Line Items]
Off-balance-sheet, credit risk	$ 13	$ 13

Amount of expected credit loss for credit exposure on off-balance-sheet commitment, including but not limited to, loan commitment, standby letter of credit, financial guarantee not accounted for as insurance. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 45
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=121611286&loc=d3e11927-110247

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 45
-Paragraph 2
-URI https://asc.fasb.org/extlink&oid=124255206&loc=SL82919202-210446

Name:	us-gaap_OffBalanceSheetCreditLossLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant