Loans Receivable and Allowance for Loan and Lease Losses Loans Receivable and ALLL (Details) - USD ($) $ in Thousands		Dec. 31, 2018	Sep. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Mar. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Receivable, before Fees, Gross		$ 424,226		$ 474,197
Unamortized premiums, deferred costs and fees, net		3,181		3,556
Allowance for loan losses		(4,802)	$ (4,792)	(5,126)	$ (5,070)	$ (5,126)	$ (5,060)
Total loans receivable, net		$ 422,605		$ 472,627
Percentage of Loan Type		100.00%		100.00%
One-to-four family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Receivable, before Fees, Gross		$ 110,105		$ 121,233
Allowance for loan losses		$ (1,463)	(1,481)	$ (1,210)	(1,127)	(1,179)	(1,663)
Percentage of Loan Type		26.00%		25.60%
Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Receivable, before Fees, Gross		$ 86,962		$ 103,887
Allowance for loan losses		$ (874)	(939)	$ (1,819)	(1,308)	(1,369)	(1,213)
Percentage of Loan Type		20.50%		21.90%
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Receivable, before Fees, Gross		$ 123,860		$ 141,835
Allowance for loan losses		$ (738)	(702)	$ (1,052)	(1,672)	(1,692)	(1,496)
Percentage of Loan Type		29.20%		29.90%
Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Receivable, before Fees, Gross	[1]	$ 98,887		$ 102,004
Allowance for loan losses		$ (1,378)	(1,530)	$ (1,003)	(777)	(832)	(573)
Percentage of Loan Type	[1]	23.30%		21.50%
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Receivable, before Fees, Gross	[2]	$ 4,412		$ 5,238
Allowance for loan losses		$ (122)	$ (140)	$ (18)	$ (21)	$ (20)	$ (9)
Percentage of Loan Type	[2]	1.00%		1.10%

[1] (1) Includes business overdrafts

[2] 2) Includes personal loans and consumer overdrafts