Nonaccrual Loans (Details) - Nonperforming - USD ($) $ in Thousands	Dec. 31, 2020	Mar. 31, 2020
Financing Receivable, Past Due [Line Items]
Financing Receivable, Nonaccrual	$ 7,477	$ 6,776
One-to-four family
Financing Receivable, Past Due [Line Items]
Financing Receivable, Nonaccrual	3,532	3,582
Multifamily
Financing Receivable, Past Due [Line Items]
Financing Receivable, Nonaccrual	372	375
Commercial real estate
Financing Receivable, Past Due [Line Items]
Financing Receivable, Nonaccrual	1,160	0
Business
Financing Receivable, Past Due [Line Items]
Financing Receivable, Nonaccrual	2,413	2,797
Consumer
Financing Receivable, Past Due [Line Items]
Financing Receivable, Nonaccrual	$ 0	$ 22