Subordinated Debentures and Subordinated Notes Payable - Summary of Subordinated Debentures and Subordinated Notes Payable (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Debt Instrument [Line Items]
Total	$ 111,873	$ 90,727
Junior subordinated debentures payable to nonconsolidated trusts
Debt Instrument [Line Items]
Amount outstanding	80,920	56,083
Common Shares Held in Other Assets	2,520	1,683
Less: fair value adjustment	(3,765)	0
Total	$ 77,155	56,083
Subordinated notes payable
Debt Instrument [Line Items]
Stated interest rate (as a percent)	4.875%
Unamortized debt issuance costs	$ (282)	(356)
Total	34,718	34,644
GW Statutory Trust IV | Junior subordinated debentures payable to nonconsolidated trusts
Debt Instrument [Line Items]
Amount outstanding	23,093	23,093
Common Shares Held in Other Assets	$ 693	$ 693
Basis spread on variable rate (as a percent)	2.85%	2.85%
GW Statutory Trust VI | Junior subordinated debentures payable to nonconsolidated trusts
Debt Instrument [Line Items]
Amount outstanding	$ 30,928	$ 30,928
Common Shares Held in Other Assets	$ 928	$ 928
Basis spread on variable rate (as a percent)	1.48%	1.48%
SSB Trust II | Junior subordinated debentures payable to nonconsolidated trusts
Debt Instrument [Line Items]
Amount outstanding	$ 2,062	$ 2,062
Common Shares Held in Other Assets	$ 62	$ 62
Basis spread on variable rate (as a percent)	1.85%	1.85%
HFB Capital Trust III | Junior subordinated debentures payable to nonconsolidated trusts
Debt Instrument [Line Items]
Amount outstanding	$ 5,155	$ 0
Common Shares Held in Other Assets	$ 155	0
Basis spread on variable rate (as a percent)	3.35%
HFB Capital Trust IV | Junior subordinated debentures payable to nonconsolidated trusts
Debt Instrument [Line Items]
Amount outstanding	$ 7,217	0
Common Shares Held in Other Assets	$ 217	0
Basis spread on variable rate (as a percent)	3.10%
HFB Capital Trust V | Junior subordinated debentures payable to nonconsolidated trusts
Debt Instrument [Line Items]
Amount outstanding	$ 10,310	0
Common Shares Held in Other Assets	$ 310	0
Basis spread on variable rate (as a percent)	1.83%
HFB Capital Trust VI | Junior subordinated debentures payable to nonconsolidated trusts
Debt Instrument [Line Items]
Amount outstanding	$ 2,155	0
Common Shares Held in Other Assets	$ 155	0
Basis spread on variable rate (as a percent)	1.65%
Subordinated notes payable, fixed to floating rate | Subordinated notes payable
Debt Instrument [Line Items]
Amount outstanding	$ 35,000	$ 35,000
Stated interest rate (as a percent)	4.875%	4.875%