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, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2018
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - Beginning Balance	$ 5,187	$ 5,133	$ 5,126	$ 5,060
Charge-offs	(480)	(26)	(590)	(141)
Recoveries	36	15	202	83
Provision for loan losses	49	4	54	124
Allowance for loan losses - Ending Balance	4,792	5,126	4,792	5,126
Allowance for Loan Losses, Collectively Evaluated for Impairment	4,120		4,120		$ 4,811
Allowance for Loan Losses, Individually Evaluated for Impairment	672		672		315
Loans, gross	431,369		431,369		477,753
Loans Receivable, Collectively Evaluated for Impairment	419,213		419,213		464,716
Loans Receivable, Individually Evaluated for Impairment	12,156		12,156		13,037
One-to-four family
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - Beginning Balance	1,853	1,518	1,210	1,663
Charge-offs	(49)	(12)	(145)	(93)
Recoveries	0	0	0	0
Provision for loan losses	(323)	(327)	416	(391)
Allowance for loan losses - Ending Balance	1,481	1,179	1,481	1,179
Allowance for Loan Losses, Collectively Evaluated for Impairment	1,309		1,309		1,065
Allowance for Loan Losses, Individually Evaluated for Impairment	172		172		145
Loans, gross	114,933		114,933		123,092
Loans Receivable, Collectively Evaluated for Impairment	109,284		109,284		116,588
Loans Receivable, Individually Evaluated for Impairment	5,649		5,649		6,504
Multifamily
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - Beginning Balance	1,387	1,227	1,819	1,213
Charge-offs	(100)	(6)	(100)	(6)
Recoveries	0	0	158	0
Provision for loan losses	(348)	148	(938)	162
Allowance for loan losses - Ending Balance	939	1,369	939	1,369
Allowance for Loan Losses, Collectively Evaluated for Impairment	939		939		1,744
Allowance for Loan Losses, Individually Evaluated for Impairment	0		0		75
Loans, gross	89,712		89,712		104,865
Loans Receivable, Collectively Evaluated for Impairment	87,384		87,384		103,160
Loans Receivable, Individually Evaluated for Impairment	2,328		2,328		1,705
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - Beginning Balance	540	1,647	1,052	1,496
Charge-offs	0	0	0	0
Recoveries	0	5	0	10
Provision for loan losses	162	40	(350)	186
Allowance for loan losses - Ending Balance	702	1,692	702	1,692
Allowance for Loan Losses, Collectively Evaluated for Impairment	702		702		1,052
Allowance for Loan Losses, Individually Evaluated for Impairment	0		0		0
Loans, gross	123,358		123,358		142,304
Loans Receivable, Collectively Evaluated for Impairment	122,869		122,869		140,765
Loans Receivable, Individually Evaluated for Impairment	489		489		1,539
Construction
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - Beginning Balance	0	0	0	106
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision for loan losses	0	0	0	(106)
Allowance for loan losses - Ending Balance	0	0	0	0
Allowance for Loan Losses, Collectively Evaluated for Impairment	0		0		0
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
Business
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - Beginning Balance	1,169	724	1,003	573
Charge-offs	(329)	0	(340)	(20)
Recoveries	4	10	9	69
Provision for loan losses	686	98	858	210
Allowance for loan losses - Ending Balance	1,530	832	1,530	832
Allowance for Loan Losses, Collectively Evaluated for Impairment	1,030		1,030		908
Allowance for Loan Losses, Individually Evaluated for Impairment	500		500		95
Loans, gross	98,732		98,732		102,203
Loans Receivable, Collectively Evaluated for Impairment	95,042		95,042		98,914
Loans Receivable, Individually Evaluated for Impairment	3,690		3,690		3,289
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - Beginning Balance	172	17	18	9
Charge-offs	(2)	(8)	(5)	(22)
Recoveries	32	0	35	4
Provision for loan losses	(62)	11	92	29
Allowance for loan losses - Ending Balance	140	20	140	20
Allowance for Loan Losses, Collectively Evaluated for Impairment	140		140		18
Allowance for Loan Losses, Individually Evaluated for Impairment	0		0		0
Loans, gross	4,634		4,634		5,289
Loans Receivable, Collectively Evaluated for Impairment	4,634		4,634		5,289
Loans Receivable, Individually Evaluated for Impairment	0		0		0
Unallocated
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - Beginning Balance	66	0	24	0
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision for loan losses	(66)	34	(24)	34
Allowance for loan losses - Ending Balance	0	$ 34	0	$ 34
Allowance for Loan Losses, Collectively Evaluated for Impairment	0		0		24
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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