Covered Assets - FDIC Indemnification Asset (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Jun. 30, 2015	Sep. 30, 2014
FDIC Indemnification Asset Movement Analysis [Roll Forward]
Balance at beginning of period	$ 36,860	$ 64,615
Additions and deletions	(1,795)	1,795
Payments made (received)	714	(2,502)
Amortization	(17,418)	(27,850)
Accretion	422	802
Balance at end of period	$ 18,783	$ 36,860