Credit Quality Indicators (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Mar. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	$ 464,199	$ 428,732
Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	97,162	89,887
Multifamily | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	96,790	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	372	375
Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	147,951	142,410
Commercial real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	145,416	141,793
Commercial real estate | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	1,375	617
Commercial real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	1,160	0
Business
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	128,641	85,659
Business | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	124,059	80,016
Business | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	1,610	2,184
Business | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	2,972	3,459
One-to-four family
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	87,569	107,528
One-to-four family | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	84,612	103,946
One-to-four family | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	2,957	3,582
Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	2,876	3,248
Consumer | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	2,876	3,225
Consumer | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	$ 0	$ 23