Loans Receivable - Troubled Debt Restructurings (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
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Contracts | contract	7	21	15	61
Pre-Modification Outstanding Recorded Investment	$ 1,101	$ 6,559	$ 2,795	$ 17,494
Troubled debt restructuring, amount	$ 1,101	$ 6,559	$ 2,795	$ 17,494
Single-family residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Contracts | contract	7	14	10	49
Pre-Modification Outstanding Recorded Investment	$ 1,101	$ 2,664	$ 1,830	$ 12,264
Troubled debt restructuring, amount	$ 1,101	$ 2,664	$ 1,830	$ 12,264
Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Contracts | contract			0	2
Pre-Modification Outstanding Recorded Investment			$ 0	$ 718
Troubled debt restructuring, amount			$ 0	$ 718
Land - consumer lot loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Contracts | contract	0	4	0	6
Pre-Modification Outstanding Recorded Investment	$ 0	$ 720	$ 0	$ 1,252
Troubled debt restructuring, amount	$ 0	$ 720	$ 0	$ 1,252
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Contracts | contract		3	5	3
Pre-Modification Outstanding Recorded Investment		$ 3,175	$ 965	$ 3,175
Troubled debt restructuring, amount		$ 3,175	$ 965	$ 3,175
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Contracts | contract			0	1
Pre-Modification Outstanding Recorded Investment			$ 0	$ 85
Troubled debt restructuring, amount			$ 0	$ 85