Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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Loans Receivable, Net - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2021	Mar. 31, 2020
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - Beginning Balance				$ 4,946				$ 4,646	$ 4,946	$ 4,646
Charge-offs									(78)	(183)
Recoveries									372	464
(Recovery of) provision for loan losses	$ (1)	$ 4	$ (1)	(102)	$ 3	$ 8	$ 7	1	(100)	19
Allowance for loan losses - Ending Balance	5,140				4,946				5,140	4,946
Allowance for Loan Losses, Collectively Evaluated for Impairment	4,982				4,780				4,982	4,780
Allowance for Loan Losses, Individually Evaluated for Impairment	158				166				158	166
Loans, gross	483,549				428,732				483,549	428,732
Loans Receivable, Collectively Evaluated for Impairment	470,681				420,282				470,681	420,282
Loans Receivable, Individually Evaluated for Impairment	12,868				8,450				12,868	8,450
One-to-four family
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - Beginning Balance				1,055				1,274	1,055	1,274
Charge-offs									0	(12)
Recoveries									88	302
(Recovery of) provision for loan losses									(85)	(509)
Allowance for loan losses - Ending Balance	1,058				1,055				1,058	1,055
Allowance for Loan Losses, Collectively Evaluated for Impairment	1,026				899				1,026	899
Allowance for Loan Losses, Individually Evaluated for Impairment	32				156				32	156
Loans, gross	78,213				107,528				78,213	107,528
Loans Receivable, Collectively Evaluated for Impairment	74,387				102,902				74,387	102,902
Loans Receivable, Individually Evaluated for Impairment	3,826				4,626				3,826	4,626
Multifamily
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - Beginning Balance				1,011				885	1,011	885
Charge-offs									0	0
Recoveries									0	0
(Recovery of) provision for loan losses									(131)	126
Allowance for loan losses - Ending Balance	880				1,011				880	1,011
Allowance for Loan Losses, Collectively Evaluated for Impairment	880				1,011				880	1,011
Allowance for Loan Losses, Individually Evaluated for Impairment	0				0				0	0
Loans, gross	106,400				89,887				106,400	89,887
Loans Receivable, Collectively Evaluated for Impairment	106,031				89,512				106,031	89,512
Loans Receivable, Individually Evaluated for Impairment	369				375				369	375
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - Beginning Balance				812				766	812	766
Charge-offs									0	0
Recoveries									0	0
(Recovery of) provision for loan losses									95	46
Allowance for loan losses - Ending Balance	907				812				907	812
Allowance for Loan Losses, Collectively Evaluated for Impairment	907				812				907	812
Allowance for Loan Losses, Individually Evaluated for Impairment	0				0				0	0
Loans, gross	148,809				142,410				148,809	142,410
Loans Receivable, Collectively Evaluated for Impairment	147,891				142,410				147,891	142,410
Loans Receivable, Individually Evaluated for Impairment	918				0				918	0
Business
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - Beginning Balance				1,567				1,330	1,567	1,330
Charge-offs									(24)	(69)
Recoveries									278	160
(Recovery of) provision for loan losses									34	146
Allowance for loan losses - Ending Balance	1,855				1,567				1,855	1,567
Allowance for Loan Losses, Collectively Evaluated for Impairment	1,729				1,557				1,729	1,557
Allowance for Loan Losses, Individually Evaluated for Impairment	126				10				126	10
Loans, gross	147,680				85,659				147,680	85,659
Loans Receivable, Collectively Evaluated for Impairment	139,925				82,210				139,925	82,210
Loans Receivable, Individually Evaluated for Impairment	7,755				3,449				7,755	3,449
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - Beginning Balance				212				154	212	154
Charge-offs									(54)	(102)
Recoveries									6	2
(Recovery of) provision for loan losses									1	158
Allowance for loan losses - Ending Balance	165				212				165	212
Allowance for Loan Losses, Collectively Evaluated for Impairment	165				212				165	212
Allowance for Loan Losses, Individually Evaluated for Impairment	0				0				0	0
Loans, gross	2,447				3,248				2,447	3,248
Loans Receivable, Collectively Evaluated for Impairment	2,447				3,248				2,447	3,248
Loans Receivable, Individually Evaluated for Impairment	0				0				0	0
Unallocated
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - Beginning Balance				$ 289				$ 237	289	237
Charge-offs									0	0
Recoveries									0	0
(Recovery of) provision for loan losses									(14)	52
Allowance for loan losses - Ending Balance	275				289				275	289
Allowance for Loan Losses, Collectively Evaluated for Impairment	275				289				275	289
Allowance for Loan Losses, Individually Evaluated for Impairment	0				0				0	0
Loans, gross	0				0				0	0
Loans Receivable, Collectively Evaluated for Impairment	0				0				0	0
Loans Receivable, Individually Evaluated for Impairment	$ 0				$ 0				$ 0	$ 0