Past Due Financing Receivables (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Mar. 31, 2020
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	$ 19,421	$ 13,913
Financing Receivable, Not Past Due	439,150	414,819
Loans, gross	458,571	428,732
Financing Receivables, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	7,604	9,984
Financing Receivables, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	997	4
Financing Receivables, Equal to Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	10,820	3,925
One-to-four family
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	3,619	4,612
Financing Receivable, Not Past Due	94,357	102,916
Loans, gross	97,976	107,528
One-to-four family | Financing Receivables, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	660	1,410
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	2,959	3,202
Multifamily
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	861	490
Financing Receivable, Not Past Due	91,264	89,397
Loans, gross	92,125	89,887
Multifamily | Financing Receivables, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	374	490
Multifamily | Financing Receivables, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	487	0
Multifamily | Financing Receivables, Equal to Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	0	0
Commercial real estate
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	12,198	6,621
Financing Receivable, Not Past Due	136,588	135,789
Loans, gross	148,786	142,410
Commercial real estate | Financing Receivables, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	5,980	6,621
Commercial real estate | Financing Receivables, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	0	0
Commercial real estate | Financing Receivables, Equal to Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	6,218	0
Business
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	2,543	2,063
Financing Receivable, Not Past Due	114,135	83,596
Loans, gross	116,678	85,659
Business | Financing Receivables, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	413	1,360
Business | Financing Receivables, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	510	3
Business | Financing Receivables, Equal to Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	1,620	700
Consumer
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	200	127
Financing Receivable, Not Past Due	2,806	3,121
Loans, gross	3,006	3,248
Consumer | Financing Receivables, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	177	103
Consumer | Financing Receivables, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	0	1
Consumer | Financing Receivables, Equal to Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	$ 23	$ 23