FDIC Indemnification Asset - Summary of FDIC Indemnification Asset Activity (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
FDIC Indemnification Asset [Roll Forward]
Balance at beginning of period	$ 10,777	$ 14,722
Amortization	(867)	(1,032)
Changes in expected reimbursements from FDIC for changes in expected credit losses	28	(128)
Changes in reimbursable expenses	(239)	(349)
Payments (reimbursements) of covered losses to (from) the FDIC	188	(28)
Balance at end of period	$ 9,887	$ 13,185