Loans Receivable and Allowance for Loan and Lease Losses Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Mar. 31, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for loan losses - Beginning Balance	$ 4,670	$ 5,187	$ 4,646	$ 5,126
Charge-offs	(62)	(480)	(129)	(590)
Recoveries	10	36	100	202
Provision for loan losses	7	49	8	54
Allowance for loan losses - Ending Balance	4,625	4,792	4,625	4,792
Allowance for Loan Losses, Collectively Evaluated for Impairment	4,443		4,443		$ 4,457
Allowance for Loan Losses, Individually Evaluated for Impairment	182		182		189
Loans, gross	433,284		433,284		428,828
Loans Receivable, Collectively Evaluated for Impairment	423,735		423,735		416,459
Loans Receivable, Individually Evaluated for Impairment	9,549		9,549		12,369
One-to-four family
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for loan losses - Beginning Balance	1,232	1,853	1,274	1,210
Charge-offs	0	(49)	0	(145)
Recoveries	8	0	8	0
Provision for loan losses	49	(323)	7	416
Allowance for loan losses - Ending Balance	1,289	1,481	1,289	1,481
Allowance for Loan Losses, Collectively Evaluated for Impairment	1,120		1,120		1,103
Allowance for Loan Losses, Individually Evaluated for Impairment	169		169		171
Loans, gross	118,502		118,502		109,926
Loans Receivable, Collectively Evaluated for Impairment	113,693		113,693		104,509
Loans Receivable, Individually Evaluated for Impairment	4,809		4,809		5,417
Multifamily
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for loan losses - Beginning Balance	875	1,387	885	1,819
Charge-offs	0	(100)	0	(100)
Recoveries	0	0	0	158
Provision for loan losses	9	(348)	(1)	(938)
Allowance for loan losses - Ending Balance	884	939	884	939
Allowance for Loan Losses, Collectively Evaluated for Impairment	884		884		885
Allowance for Loan Losses, Individually Evaluated for Impairment	0		0		0
Loans, gross	82,823		82,823		86,886
Loans Receivable, Collectively Evaluated for Impairment	80,390		80,390		83,672
Loans Receivable, Individually Evaluated for Impairment	2,433		2,433		3,214
Commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for loan losses - Beginning Balance	668	540	766	1,052
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision for loan losses	27	162	(71)	(350)
Allowance for loan losses - Ending Balance	695	702	695	702
Allowance for Loan Losses, Collectively Evaluated for Impairment	695		695		766
Allowance for Loan Losses, Individually Evaluated for Impairment	0		0		0
Loans, gross	137,451		137,451		131,292
Loans Receivable, Collectively Evaluated for Impairment	137,451		137,451		130,816
Loans Receivable, Individually Evaluated for Impairment	0		0		476
Business
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for loan losses - Beginning Balance	1,400	1,169	1,330	1,003
Charge-offs	(56)	(329)	(56)	(340)
Recoveries	2	4	90	9
Provision for loan losses	145	686	127	858
Allowance for loan losses - Ending Balance	1,491	1,530	1,491	1,530
Allowance for Loan Losses, Collectively Evaluated for Impairment	1,478		1,478		1,312
Allowance for Loan Losses, Individually Evaluated for Impairment	13		13		18
Loans, gross	90,816		90,816		96,661
Loans Receivable, Collectively Evaluated for Impairment	88,509		88,509		93,399
Loans Receivable, Individually Evaluated for Impairment	2,307		2,307		3,262
Consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for loan losses - Beginning Balance	240	172	154	18
Charge-offs	(6)	(2)	(73)	(5)
Recoveries	0	32	2	35
Provision for loan losses	14	(62)	165	92
Allowance for loan losses - Ending Balance	248	140	248	140
Allowance for Loan Losses, Collectively Evaluated for Impairment	248		248		154
Allowance for Loan Losses, Individually Evaluated for Impairment	0		0		0
Loans, gross	3,692		3,692		4,063
Loans Receivable, Collectively Evaluated for Impairment	3,692		3,692		4,063
Loans Receivable, Individually Evaluated for Impairment	0		0		0
Unallocated
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for loan losses - Beginning Balance	255	66	237	24
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision for loan losses	(237)	(66)	(219)	(24)
Allowance for loan losses - Ending Balance	18	$ 0	18	$ 0
Allowance for Loan Losses, Collectively Evaluated for Impairment	18		18		237
Allowance for Loan Losses, Individually Evaluated for Impairment	0		0		0
Loans, gross	0		0		0
Loans Receivable, Collectively Evaluated for Impairment	0		0		0
Loans Receivable, Individually Evaluated for Impairment	$ 0		$ 0		$ 0

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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The balance of financing receivables that were collectively evaluated for impairment.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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Amount of expense related to estimated loss from loan and lease transactions.

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