Loans Receivable - Loan Modifications (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2017 USD ($) contract	Jun. 30, 2016 USD ($) contract	Jun. 30, 2017 USD ($) contract	Jun. 30, 2016 USD ($) contract
Financing Receivable, Modifications [Line Items]
Number of contracts (in contracts) | contract	3	7	18	21
Recorded investment | $	$ 401	$ 2,227	$ 3,853	$ 4,211
Single-family residential
Financing Receivable, Modifications [Line Items]
Number of contracts (in contracts) | contract	3	3	16	14
Recorded investment | $	$ 401	$ 1,570	$ 3,586	$ 3,108
Construction
Financing Receivable, Modifications [Line Items]
Number of contracts (in contracts) | contract	0	1	0	1
Recorded investment | $	$ 0	$ 279	$ 0	$ 279
Land - consumer lot loans
Financing Receivable, Modifications [Line Items]
Number of contracts (in contracts) | contract	0	2	0	4
Recorded investment | $	$ 0	$ 204	$ 0	$ 498
Commercial real estate
Financing Receivable, Modifications [Line Items]
Number of contracts (in contracts) | contract	0	1	2	2
Recorded investment | $	$ 0	$ 174	$ 267	$ 326