Loans Receivable - Loan Modifications (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2016 USD ($) contract	Mar. 31, 2015 USD ($) contract	Mar. 31, 2016 USD ($) contract	Mar. 31, 2015 USD ($) contract
Financing Receivable, Modifications [Line Items]
Number of contracts (in contracts) | contract	8	4	10	10
Recorded investment | $	$ 1,169	$ 605	$ 1,393	$ 1,626
Single-family residential
Financing Receivable, Modifications [Line Items]
Number of contracts (in contracts) | contract	6	2	8	7
Recorded investment | $	$ 871	$ 304	$ 1,095	$ 1,237
Land - consumer lot loans
Financing Receivable, Modifications [Line Items]
Number of contracts (in contracts) | contract	1	2	1	3
Recorded investment | $	$ 146	$ 301	$ 146	$ 389
Commercial real estate
Financing Receivable, Modifications [Line Items]
Number of contracts (in contracts) | contract	1	0	1	0
Recorded investment | $	$ 152	$ 0	$ 152	$ 0