Loans Receivable and ALLL (Details) - USD ($) $ in Thousands		Dec. 31, 2020	Sep. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Mar. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Receivable, before Fees, Gross		$ 465,815		$ 425,172
Unamortized premiums, deferred costs and fees, net		2,778		3,560
Allowance for loan losses		(5,138)	$ (4,916)	(4,946)	$ (4,607)	$ (4,625)	$ (4,646)
Total loans receivable, net		$ 463,455		$ 423,786
Percentage of Loan Type		100.00%		100.00%
Other Real Estate Owned		$ 60		$ 120
Financing Receivable, Troubled Debt Restructuring		7,600		3,900
One-to-four family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Receivable, before Fees, Gross		81,678		105,532
Allowance for loan losses		$ (864)	(953)	$ (1,055)	(1,181)	(1,289)	(1,274)
Percentage of Loan Type		17.50%		24.80%
Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Receivable, before Fees, Gross		$ 107,089		$ 89,241
Allowance for loan losses		$ (1,027)	(960)	$ (1,011)	(920)	(884)	(885)
Percentage of Loan Type		23.00%		21.00%
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Receivable, before Fees, Gross		$ 146,742		$ 141,761
Allowance for loan losses		$ (966)	(969)	$ (812)	(691)	(695)	(766)
Percentage of Loan Type		31.50%		33.30%
Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Receivable, before Fees, Gross	[1]	$ 127,579		$ 85,425
Allowance for loan losses		$ (1,838)	(1,636)	$ (1,567)	(1,484)	(1,491)	(1,330)
Percentage of Loan Type	[1]	27.40%		20.10%
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Receivable, before Fees, Gross	[2]	$ 2,727		$ 3,213
Allowance for loan losses		$ (190)	$ (189)	$ (212)	$ (231)	$ (248)	$ (154)
Percentage of Loan Type	[2]	0.60%		0.80%

[1] (1) Includes PPP loans and business overdrafts

[2] 2) Includes personal loans and consumer overdrafts