Loans Receivable and Allowance for Loan and Lease Losses Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Mar. 31, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - Beginning Balance	$ 5,133	$ 5,183	$ 5,060	$ 5,232	$ 5,232
Charge-offs	26	344	141	354	529
Recoveries	15	68	83	233	328
Provision for loan losses	4	(160)	124	(364)	29
Allowance for loan losses - Ending Balance	5,126	4,747	5,126	4,747	5,060
Allowance for Loan Losses, Collectively Evaluated for Impairment	4,849	4,288	4,849	4,288	4,699
Allowance for Loan Losses, Individually Evaluated for Impairment	277	459	277	459	361
Loans, gross	518,543	528,755	518,543	528,755	545,552
Loans Receivable, Collectively Evaluated for Impairment	503,995	512,625	503,995	512,625	530,859
Loans Receivable, Individually Evaluated for Impairment	14,548	16,130	14,548	16,130	14,693
One-to-four family
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - Beginning Balance	1,518	1,875	1,663	1,697	1,697
Charge-offs	12	59	93	62	106
Recoveries	0	0	0	0	0
Provision for loan losses	(327)	(162)	(391)	19	72
Allowance for loan losses - Ending Balance	1,179	1,654	1,179	1,654	1,663
Allowance for Loan Losses, Collectively Evaluated for Impairment	1,031	1,423	1,031	1,423	1,357
Allowance for Loan Losses, Individually Evaluated for Impairment	148	231	148	231	306
Loans, gross	130,480	130,673	130,480	130,673	134,927
Loans Receivable, Collectively Evaluated for Impairment	123,381	125,352	123,381	125,352	129,420
Loans Receivable, Individually Evaluated for Impairment	7,099	5,321	7,099	5,321	5,507
Multifamily
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - Beginning Balance	1,227	530	1,213	622	622
Charge-offs	6	244	6	251	338
Recoveries	0	0	0	0	0
Provision for loan losses	148	386	162	301	929
Allowance for loan losses - Ending Balance	1,369	672	1,369	672	1,213
Allowance for Loan Losses, Collectively Evaluated for Impairment	1,308	672	1,308	672	1,207
Allowance for Loan Losses, Individually Evaluated for Impairment	61	0	61	0	6
Loans, gross	81,765	74,751	81,765	74,751	88,750
Loans Receivable, Collectively Evaluated for Impairment	80,183	73,141	80,183	73,141	87,148
Loans Receivable, Individually Evaluated for Impairment	1,582	1,610	1,582	1,610	1,602
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - Beginning Balance	1,647	1,858	1,496	1,808	1,808
Charge-offs	0	0	0	0	0
Recoveries	5	5	10	10	20
Provision for loan losses	40	(120)	186	(75)	(332)
Allowance for loan losses - Ending Balance	1,692	1,743	1,692	1,743	1,496
Allowance for Loan Losses, Collectively Evaluated for Impairment	1,692	1,722	1,692	1,722	1,490
Allowance for Loan Losses, Individually Evaluated for Impairment	0	20	0	20	6
Loans, gross	224,919	251,988	224,919	251,988	242,818
Loans Receivable, Collectively Evaluated for Impairment	223,537	249,145	223,537	249,145	239,323
Loans Receivable, Individually Evaluated for Impairment	1,382	2,843	1,382	2,843	3,495
Construction
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - Beginning Balance	0	62	106	62	62
Charge-offs	0	0	0	0	0
Recoveries	0	0	0	0	0
Provision for loan losses	0	(12)	(106)	(12)	44
Allowance for loan losses - Ending Balance	0	50	0	50	106
Allowance for Loan Losses, Collectively Evaluated for Impairment	0	50	0	50	106
Allowance for Loan Losses, Individually Evaluated for Impairment	0	0	0	0	0
Loans, gross	0	4,975	0	4,975	4,949
Loans Receivable, Collectively Evaluated for Impairment	0	4,975	0	4,975	4,949
Loans Receivable, Individually Evaluated for Impairment	0	0	0	0	0
Business
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - Beginning Balance	724	856	573	1,022	1,022
Charge-offs	0	0	20	0	0
Recoveries	10	63	69	219	304
Provision for loan losses	98	(342)	210	(664)	(753)
Allowance for loan losses - Ending Balance	832	577	832	577	573
Allowance for Loan Losses, Collectively Evaluated for Impairment	764	370	764	370	532
Allowance for Loan Losses, Individually Evaluated for Impairment	68	208	68	208	41
Loans, gross	72,991	66,118	72,991	66,118	65,114
Loans Receivable, Collectively Evaluated for Impairment	68,506	59,762	68,506	59,762	61,027
Loans Receivable, Individually Evaluated for Impairment	4,485	6,356	4,485	6,356	4,087
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - Beginning Balance	17	2	9	21	21
Charge-offs	8	41	22	41	85
Recoveries	0	0	4	4	4
Provision for loan losses	11	41	29	18	69
Allowance for loan losses - Ending Balance	20	2	20	2	9
Allowance for Loan Losses, Collectively Evaluated for Impairment	20	2	20	2	7
Allowance for Loan Losses, Individually Evaluated for Impairment	0	0	0	0	2
Loans, gross	8,388	250	8,388	250	8,994
Loans Receivable, Collectively Evaluated for Impairment	8,388	250	8,388	250	8,992
Loans Receivable, Individually Evaluated for Impairment	0	0	0	0	2
Unallocated
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - Beginning Balance	0	0	0	0	0
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision for loan losses	34	49	34	49
Allowance for loan losses - Ending Balance	34	49	34	49	$ 0
Allowance for Loan Losses, Collectively Evaluated for Impairment	34	49	34	49
Allowance for Loan Losses, Individually Evaluated for Impairment	0	0	0	0
Loans, gross	0	0	0	0
Loans Receivable, Collectively Evaluated for Impairment	0	0	0	0
Loans Receivable, Individually Evaluated for Impairment	$ 0	$ 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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