Past Due Financing Receivables (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Mar. 31, 2019
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	$ 15,972	$ 11,625
Financing Receivable, Not Past Due	406,347	417,203
Loans, gross	422,319	428,828
Financing Receivables, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	8,626	5,395
Financing Receivables, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	1,848	53
Financing Receivables, Equal to Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	5,498	6,177
One-to-four family
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	4,864	5,222
Financing Receivable, Not Past Due	108,488	104,704
Loans, gross	113,352	109,926
One-to-four family | Financing Receivables, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	1,196	1,827
One-to-four family | Financing Receivables, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	0	0
One-to-four family | Financing Receivables, Equal to Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	3,668	3,395
Multifamily
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	505	4,698
Financing Receivable, Not Past Due	83,567	82,188
Loans, gross	84,072	86,886
Multifamily | Financing Receivables, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	0	2,580
Multifamily | Financing Receivables, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	505	0
Multifamily | Financing Receivables, Equal to Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	0	2,118
Commercial real estate
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	5,984	121
Financing Receivable, Not Past Due	129,440	131,171
Loans, gross	135,424	131,292
Commercial real estate | Financing Receivables, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	4,651	121
Commercial real estate | Financing Receivables, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	1,333	0
Commercial real estate | Financing Receivables, Equal to Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	0	0
Business
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	4,611	1,379
Financing Receivable, Not Past Due	81,272	95,282
Loans, gross	85,883	96,661
Business | Financing Receivables, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	2,777	780
Business | Financing Receivables, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	4	0
Business | Financing Receivables, Equal to Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	1,830	599
Consumer
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	8	205
Financing Receivable, Not Past Due	3,580	3,858
Loans, gross	3,588	4,063
Consumer | Financing Receivables, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	2	87
Consumer | Financing Receivables, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	6	53
Consumer | Financing Receivables, Equal to Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	$ 0	$ 65