Securities Available for Sale - Schedule of Gross Unrealized Losses (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Sep. 30, 2015
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months, Fair Value	$ 45,461	$ 63,588
12 months or more, Fair Value	284,995	412,058
Estimated Fair Value	330,456	475,646
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 months, Unrealized Losses	(170)	(249)
12 months or more, Unrealized Losses	(1,916)	(4,480)
Unrealized Losses	(2,086)	(4,729)
Mortgage-backed securities
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months, Fair Value	17,528	58,604
12 months or more, Fair Value	284,995	412,058
Estimated Fair Value	302,523	470,662
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 months, Unrealized Losses	(6)	(236)
12 months or more, Unrealized Losses	(1,916)	(4,480)
Unrealized Losses	(1,922)	(4,716)
States and political subdivision securities
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months, Fair Value	27,933	0
12 months or more, Fair Value	0	0
Estimated Fair Value	27,933	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 months, Unrealized Losses	(164)	0
12 months or more, Unrealized Losses	0	0
Unrealized Losses	(164)	0
Other
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months, Fair Value	0	4,984
12 months or more, Fair Value	0	0
Estimated Fair Value	0	4,984
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 months, Unrealized Losses	0	(13)
12 months or more, Unrealized Losses	0	0
Unrealized Losses	$ 0	$ (13)