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Loans Receivable - Loan Modifications (Details) $ in Thousands	3 Months Ended
	Dec. 31, 2017 USD ($) contract	Dec. 31, 2016 USD ($) contract
Financing Receivable, Modifications [Line Items]
Number of contracts | contract	1	8
Recorded investment | $	$ 44	$ 2,260
Single-family residential
Financing Receivable, Modifications [Line Items]
Number of contracts | contract	1	6
Recorded investment | $	$ 44	$ 1,993
Commercial real estate
Financing Receivable, Modifications [Line Items]
Number of contracts | contract	0	2
Recorded investment | $	$ 0	$ 267

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- Definition

Financing Receivable, Modifications, Number of Contracts that Subsequently Defaulted

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- Definition

Financing Receivable, Modifications, Recorded Investment During the Period

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