Debt Obligations - Junior Subordinated Notes (Details) - USD ($) $ in Thousands			3 Months Ended		9 Months Ended
	Jun. 30, 2015	Sep. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Debt Instrument [Line Items]
Total debt obligations	$ 520,932	$ 519,806	$ 520,932		$ 520,932
Junior subordinated notes
Debt Instrument [Line Items]
Total debt obligations	$ 37,400	$ 37,400	37,400		37,400
Interest Expense			458	$ 458	1,375	$ 1,375
Amortization of deferred costs included in interest expense			$ 5,000	$ 5,000	$ 15,000	$ 15,000
Debt Instrument, Interest Rate 1 August, 2012 Through 29 April, 2016 [Member] | Junior subordinated notes
Debt Instrument [Line Items]
Interest Rate	4.90%	4.90%	4.90%		4.90%
Debt Instrument, Interest Rate 30 April, 2016 Through 30 April, 2036 [Member] | Junior subordinated notes
Debt Instrument [Line Items]
Description of variable rate basis	LIBOR	LIBOR
Basis spread on variable rate	2.00%	2.00%