Loans Receivable - Loan Modifications (Details) $ in Thousands	3 Months Ended
	Dec. 31, 2016 USD ($) contract	Dec. 31, 2015 USD ($) contract
Financing Receivable, Modifications [Line Items]
Number of contracts (in contracts) | contract	8	6
Recorded investment | $	$ 2,260	$ 816
Single-family residential
Financing Receivable, Modifications [Line Items]
Number of contracts (in contracts) | contract	6	5
Recorded investment | $	$ 1,993	$ 668
Land - consumer lot loans
Financing Receivable, Modifications [Line Items]
Number of contracts (in contracts) | contract	0	1
Recorded investment | $	$ 0	$ 148
Commercial real estate
Financing Receivable, Modifications [Line Items]
Number of contracts (in contracts) | contract	2	0
Recorded investment | $	$ 267	$ 0