Credit Quality Indicators (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Mar. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	$ 468,593	$ 428,732
Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	107,723	89,887
Multifamily | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	102,531	89,512
Multifamily | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	0	0
Multifamily | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	5,192	375
Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	147,520	142,410
Commercial real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	143,872	141,793
Commercial real estate | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	2,296	617
Commercial real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	1,352	0
Business
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	127,548	85,659
Business | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	115,591	80,016
Business | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	3,102	2,184
Business | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	8,855	3,459
One-to-four family
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	83,047	107,528
One-to-four family | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	79,711	103,946
One-to-four family | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	3,336	3,582
Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	2,755	3,248
Consumer | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	2,755	3,225
Consumer | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	$ 0	$ 23