Loans Receivable, Net - Credit Quality Indicators (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Mar. 31, 2019
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	$ 428,732	$ 428,828
Multifamily
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	89,887	86,886
Multifamily | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	89,512	83,672
Multifamily | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	0	0
Multifamily | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	375	3,214
Multifamily | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	0
Multifamily | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	0
Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	142,410	131,292
Commercial real estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	141,793	128,319
Commercial real estate | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	617	2,497
Commercial real estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	0	476
Commercial real estate | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	0
Commercial real estate | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	0
Business
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	85,659	96,661
Business | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	80,016	90,336
Business | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	2,184	2,425
Business | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	3,459	3,900
Business | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	0
Business | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	0
One-to-four family
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	107,528	109,926
One-to-four family | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	103,946	106,531
One-to-four family | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	3,582	3,395
Consumer
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	3,248	4,063
Consumer | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	3,225	4,063
Consumer | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	$ 23	$ 0