Loans Receivable and Allowance for Loan and Lease Losses Credit Quality Indicators (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Mar. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	$ 533,692	$ 545,552
Multifamily
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	83,234	88,750
Multifamily | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	81,639	87,148
Multifamily | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	0	0
Multifamily | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	1,595	1,082
Multifamily | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	0	520
Multifamily | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	0	0
Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	242,743	242,818
Commercial real estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	238,971	238,552
Commercial real estate | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	763	771
Commercial real estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	3,009	3,495
Commercial real estate | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	0	0
Commercial real estate | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	0	0
Construction
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	0	4,949
Construction | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	0	4,949
Construction | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	0	0
Construction | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	0	0
Construction | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	0	0
Construction | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	0	0
Business
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	67,968	65,114
Business | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	60,923	58,555
Business | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	1,571	133
Business | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	5,474	6,426
Business | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	0	0
Business | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	0	0
One-to-four family
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	131,134	134,927
One-to-four family | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	124,905	131,028
One-to-four family | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	6,229	3,899
Consumer
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	8,613	8,994
Consumer | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	8,613	8,992
Consumer | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans, gross	$ 0	$ 2