Loans - Recorded investment in loans based on impairment method (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	$ 2,406	$ 2,361	$ 2,361
Charge offs	0	(2)	(20)
Recoveries	0	0	5
Provisions	40	0	60
Ending balance	2,446	2,359	2,406
Individually evaluated for impairment	0	0	0
Collectively evaluated for impairment	2,446	2,359	2,406
Loans individually evaluated for impairment	3,422	7,627	3,440
Loans collectively evaluated for impairment	266,563	231,186	251,172
Total ending loans balance	269,985	238,813	254,612
Commercial Loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	145	187	187
Charge offs	0	0	0
Recoveries	0	0	0
Provisions	21	(6)	(42)
Ending balance	166	181	145
Individually evaluated for impairment	0	0	0
Collectively evaluated for impairment	166	181	145
Loans individually evaluated for impairment	126	1,071	237
Loans collectively evaluated for impairment	25,292	23,465	23,975
Total ending loans balance	25,418	24,536	24,212
Consumer Loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	66	64	64
Charge offs	0	(2)	(14)
Recoveries	0	0	5
Provisions	18	4	11
Ending balance	84	66	66
Individually evaluated for impairment	0	0	0
Collectively evaluated for impairment	84	66	66
Loans individually evaluated for impairment	0	0	0
Loans collectively evaluated for impairment	7,614	6,010	6,431
Total ending loans balance	7,614	6,010	6,431
One To Four Family [Member] \| Real estate loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	1,355	1,300	1,300
Charge offs	0	0	(6)
Recoveries	0	0	0
Provisions	(23)	(21)	61
Ending balance	1,332	1,279	1,355
Individually evaluated for impairment	0	0	0
Collectively evaluated for impairment	1,332	1,279	1,355
Loans individually evaluated for impairment	121	439	14
Loans collectively evaluated for impairment	133,598	115,794	127,740
Total ending loans balance	133,719	116,233	127,754
Multifamily [Member] \| Real estate loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	19	27	27
Charge offs	0	0	0
Recoveries	0	0	0
Provisions	(3)	(1)	(8)
Ending balance	16	26	19
Individually evaluated for impairment	0	0	0
Collectively evaluated for impairment	16	26	19
Loans individually evaluated for impairment	0	0	0
Loans collectively evaluated for impairment	3,261	4,764	3,730
Total ending loans balance	3,261	4,764	3,730
Commercial [Member] \| Real estate loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	712	746	746
Charge offs	0	0	0
Recoveries	0	0	0
Provisions	20	(7)	(34)
Ending balance	732	739	712
Individually evaluated for impairment	0	0	0
Collectively evaluated for impairment	732	739	712
Loans individually evaluated for impairment	3,175	6,117	3,189
Loans collectively evaluated for impairment	80,497	71,797	73,778
Total ending loans balance	83,672	77,914	76,967
Construction [Member] \| Real estate loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	109	37	37
Charge offs	0	0	0
Recoveries	0	0	0
Provisions	7	31	72
Ending balance	116	68	109
Individually evaluated for impairment	0	0	0
Collectively evaluated for impairment	116	68	109
Loans individually evaluated for impairment	0	0	0
Loans collectively evaluated for impairment	16,301	9,356	15,518
Total ending loans balance	$ 16,301	$ 9,356	$ 15,518

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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Amount of increase in allowance for credit loss on financing receivable from recovery.

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Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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