Loans Receivable and the Allowance for Loan Losses - Summary of recorded investment, unpaid principal balance and allocated allowance (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Recorded Investment
Recorded Investment, With no related allowance	$ 1,634	$ 6,311	$ 1,634	$ 6,311	$ 1,622
Recorded Investment	1,634	6,311	1,634	6,311	1,622
Unpaid Principal Balance
Unpaid Principal Balance, With no related allowance	1,701	6,378	1,701	6,378	1,689
Unpaid Principal Balance	1,701	6,378	1,701	6,378	1,689
Average Recorded Investment
Average Recorded Investment, With no related allowance	1,633	6,323	1,629	6,372	5,877
Average Recorded Investment	1,633	6,323	1,629	6,372	5,877
Interest Income Recognized
Interest Income Recognized, With no related allowance	20	32	36	62	122
Interest Income Recognized	20	32	36	62	122
Residential real estate \| Multi-family
Recorded Investment
Recorded Investment, With no related allowance	865	1,977	865	1,977	876
Recorded Investment	865	1,977	865	1,977	876
Unpaid Principal Balance
Unpaid Principal Balance, With no related allowance	865	1,977	865	1,977	876
Unpaid Principal Balance	865	1,977	865	1,977	876
Average Recorded Investment
Average Recorded Investment, With no related allowance	865	1,986	869	1,994	1,986
Average Recorded Investment	865	1,986	869	1,994	1,986
Interest Income Recognized
Interest Income Recognized, With no related allowance	16	24	22	45	86
Interest Income Recognized	16	24	22	45	86
Non-residential real estate
Recorded Investment
Recorded Investment, With no related allowance	769	4,334	769	4,334	746
Recorded Investment	769	4,334	769	4,334	746
Unpaid Principal Balance
Unpaid Principal Balance, With no related allowance	836	4,401	836	4,401	813
Unpaid Principal Balance	836	4,401	836	4,401	813
Average Recorded Investment
Average Recorded Investment, With no related allowance	768	4,337	760	4,378	3,891
Average Recorded Investment	768	4,337	760	4,378	3,891
Interest Income Recognized
Interest Income Recognized, With no related allowance	4	8	14	17	36
Interest Income Recognized	$ 4	$ 8	$ 14	$ 17	$ 36

Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI https://asc.fasb.org/extlink&oid=123577603&loc=d3e5212-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI https://asc.fasb.org/extlink&oid=123577603&loc=d3e5258-111524

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