Securities Available for Sale - Schedule of Available For Sale Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Sep. 30, 2015
Amortized Cost
Due in one year or less	$ 3,706	$ 76,261
Due after one year through five years	265,253	255,982
Due after five years through ten years	18,449	0
Due after ten years	122	0
Amortized Cost	287,530	332,243
Estimated Fair Value
Due in one year or less	3,709	76,905
Due after one year through five years	269,242	259,780
Due after five years through ten years	18,413	0
Due after ten years	122	0
Estimated Fair Value	291,486	336,685
Amortized Cost	1,308,445	1,323,573
Estimated Fair Value	1,317,386	1,327,327
Securities without contractual maturities, Amortized Cost	1,013	1,006
Securities without contractual maturities, Fair Value	1,062	1,042
Mortgage-backed securities
Estimated Fair Value
Amortized Cost	1,019,902	990,324
Estimated Fair Value	$ 1,024,838	$ 989,600