Loans Receivable, Net - Text Tag (Details)	12 Months Ended
	Mar. 31, 2023 USD ($)	Mar. 31, 2022 USD ($)	Mar. 31, 2021 USD ($)
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts	3	0
Financing Receivable, Modifications, Recorded Investment	$ 7,600,000	$ 6,900,000
Financing Receivable, Number of Principal and Interest Payment Deferrals			83
Financing Receivable, Principal and Interest Deferred Payments			$ 90,400,000
FNMA & 3rd party loans excluded from financial statements	12,600,000	$ 14,500,000
Number of Loans Originated Under the Paycheck Protection Program		420
Loans Originated Under the Paycheck Protection Program, Amount		$ 57,100,000
Financing Receivable, Principal and Interest Deferred Payments			$ 90,400,000
Other non-performing asset	$ 60,000	$ 60,000
Number of Real Estate Properties	1	1
Loans held-for-sale (HFS)	$ 0	$ 0
Loans Receivable, Impaired, Interest Lost on Nonaccrual Loans	189,000	266,000
Loans 90 Days Past Due and Still Accruing	$ 0	$ 0
Modified Loan Subsequently Defaulted	0	0
Loans and Leases Receivable, Related Parties	$ 30,000	$ 30,000
Loans and Leases Receivable, Related Parties, Additions	0
Loans and Leases Receivable, Related Parties, Proceeds	0
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Purchase	14,300,000	50,100,000
Asset Pledged as Collateral | Federal Home Loan Bank Advances
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	53,500,000
Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Purchase		15,100,000
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Purchase	5,800,000	18,200,000
Business
Financing Receivable, Modifications [Line Items]
Overdrafts	11,000	5,000
Accounts, Notes, Loans and Financing Receivable [Line Items]
Overdrafts	11,000	5,000
Financing Receivable, Purchase	613,000	5,600,000
Consumer
Financing Receivable, Modifications [Line Items]
Overdrafts	19,000	31,000
Accounts, Notes, Loans and Financing Receivable [Line Items]
Overdrafts	19,000	31,000
Financing Receivable, Purchase	$ 3,900,000
One-to-four family
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts	3
Financing Receivable, Modifications, Pre-Modification Recorded Investment	$ 1,357,000
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Purchase	4,000,000	11,300,000
Non-performing
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Recorded Investment	$ 1,600,000	$ 1,700,000