Borrowings - Schedule of Long-term Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Sep. 30, 2015
Debt Instrument [Line Items]
Unamortized debt discounts	$ (5,272)	$ (3,639)
Notes Payable	1,459,605	1,528,275
Total debt, net	1,459,605	1,528,275
Senior Notes
Debt Instrument [Line Items]
Unamortized debt discounts	(3,259)	(3,639)
Notes Payable	$ 1,246,309	$ 1,427,240
Senior Notes | 8 1/8% Senior Notes Maturing June 2016
Debt Instrument [Line Items]
Stated interest rate on debt instrument (percent)	8.125%	8.125%
Notes Payable	$ 0	$ 170,879
Senior Notes | 6 5/8% Senior Secured Notes April 2018
Debt Instrument [Line Items]
Stated interest rate on debt instrument (percent)	6.625%	6.625%
Notes Payable	$ 300,000	$ 300,000
Senior Notes | 9 1/8% Senior Notes Maturing May 2019
Debt Instrument [Line Items]
Stated interest rate on debt instrument (percent)	9.125%	9.125%
Notes Payable	$ 225,175	$ 235,000
Senior Notes | 5 3/4% Senior Notes Maturing June 2019
Debt Instrument [Line Items]
Stated interest rate on debt instrument (percent)	5.75%	5.75%
Notes Payable	$ 324,393	$ 325,000
Senior Notes | 7 1/2% Senior Notes Maturing September 2021
Debt Instrument [Line Items]
Stated interest rate on debt instrument (percent)	7.50%	7.50%
Notes Payable	$ 200,000	$ 200,000
Senior Notes | 7 1/4% Senior Notes Maturing February 2023
Debt Instrument [Line Items]
Stated interest rate on debt instrument (percent)	7.25%	7.25%
Notes Payable	$ 200,000	$ 200,000
Term Loan
Debt Instrument [Line Items]
Unamortized debt discounts	(2,013)
Notes Payable	$ 137,987	0
Junior Subordinated Notes
Debt Instrument [Line Items]
Stated interest rate on debt instrument (percent)	7.987%
Unamortized debt discounts	$ (41,900)	(43,000)
Notes Payable	58,837	57,803
Cash Secured Loan
Debt Instrument [Line Items]
Notes Payable	0	22,368
Other Secured Notes Payable
Debt Instrument [Line Items]
Notes Payable	$ 16,472	$ 20,864