Loans Receivable, Net - Credit Quality Indicators (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Mar. 31, 2020
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	$ 483,549	$ 428,732
Multifamily
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	106,400	89,887
Multifamily | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	101,212	89,512
Multifamily | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	0	0
Multifamily | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	5,188	375
Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	148,809	142,410
Commercial real estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	142,168	141,793
Commercial real estate | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	5,531	617
Commercial real estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	1,110	0
Business
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	147,680	85,659
Business | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	137,447	80,016
Business | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	1,585	2,184
Business | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	8,648	3,459
One-to-four family
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	78,213	107,528
One-to-four family | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	74,689	103,946
One-to-four family | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	3,524	3,582
Consumer
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	2,447	3,248
Consumer | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	2,356	3,225
Consumer | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	$ 91	$ 23