Loans Receivable, Net - Past Due Financing Receivables (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Mar. 31, 2020
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss		$ 414,819
Loans, gross	$ 483,549	428,732
Financing Receivables, 30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	7,922	9,984
Financing Receivables, 60 to 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	433	4
Financing Receivables, Equal to Greater than 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,312	3,925
Financial Asset, Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	11,667	13,913
Financial Asset, Not Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	471,882
One-to-four family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, gross	78,213	107,528
One-to-four family | Financing Receivables, 30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,188	1,410
One-to-four family | Financing Receivables, 60 to 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
One-to-four family | Financing Receivables, Equal to Greater than 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,950	3,202
One-to-four family | Financial Asset, Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	4,138	4,612
One-to-four family | Financial Asset, Not Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	74,075	102,916
Multifamily
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, gross	106,400	89,887
Multifamily | Financing Receivables, 30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	798	490
Multifamily | Financing Receivables, 60 to 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
Multifamily | Financing Receivables, Equal to Greater than 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
Multifamily | Financial Asset, Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	798	490
Multifamily | Financial Asset, Not Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	105,602	89,397
Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, gross	148,809	142,410
Commercial real estate | Financing Receivables, 30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	5,263	6,621
Commercial real estate | Financing Receivables, 60 to 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
Commercial real estate | Financing Receivables, Equal to Greater than 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
Commercial real estate | Financial Asset, Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	5,263	6,621
Commercial real estate | Financial Asset, Not Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	143,546	135,789
Business
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, gross	147,680	85,659
Business | Financing Receivables, 30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	671	1,360
Business | Financing Receivables, 60 to 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	400	3
Business | Financing Receivables, Equal to Greater than 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	271	700
Business | Financial Asset, Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,342	2,063
Business | Financial Asset, Not Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	146,338	83,596
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, gross	2,447	3,248
Consumer | Financing Receivables, 30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2	103
Consumer | Financing Receivables, 60 to 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	33	1
Consumer | Financing Receivables, Equal to Greater than 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	91	23
Consumer | Financial Asset, Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	126	127
Consumer | Financial Asset, Not Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 2,321	$ 3,121