Borrowings - Schedule of Long-term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Sep. 30, 2015
Debt Instrument [Line Items]
Unamortized debt discounts	$ (3,449)	$ (3,639)
Notes Payable	1,502,056	1,528,275
Total debt (net of discounts of $3,449 and $3,639, respectively)	1,502,056	1,528,275
Senior Notes
Debt Instrument [Line Items]
Unamortized debt discounts	(3,449)	(3,639)
Notes Payable	$ 1,404,555	$ 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	$ 148,004	$ 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	$ 235,000	$ 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	$ 325,000	$ 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
Junior Subordinated Notes
Debt Instrument [Line Items]
Stated interest rate on debt instrument (percent)	7.987%
Unamortized debt discounts	$ (42,500)
Notes Payable	58,320	57,803
Cash Secured Loan
Debt Instrument [Line Items]
Notes Payable	22,368	22,368
Other Secured Notes Payable
Debt Instrument [Line Items]
Notes Payable	$ 16,813	$ 20,864