Securities Available for Sale - Unrealized Gain (Loss) On Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance accumulated other comprehensive income (loss)	$ 2,318	$ (6,157)	$ (7,081)
Net unrealized holding gain arising during the year	5,347	13,979	1,400
Reclassification adjustment for net (gain) realized in net income	(160)	(310)	(90)
Net change in unrealized gain before income taxes	5,187	13,669	1,310
Income tax (expense)	(1,971)	(5,194)	(386)
Net change in unrealized gain on securities after taxes	3,216	8,475	924
Ending balance accumulated other comprehensive income (loss)	$ 5,534	$ 2,318	$ (6,157)