Borrowings - Schedule of Debt Redemption (Details) - Senior Notes	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
5 3/4% Senior Notes Maturing June 2019
Debt Instrument, Redemption [Line Items]
Debt instrument stated interest rate (percent)	5.75%	5.75%
5 3/4% Senior Notes Maturing June 2019 | Debt Instrument, Redemption, Period One
Debt Instrument, Redemption [Line Items]
Debt Instrument, redemption price percentage	100.00%
7 1/2% Senior Notes Maturing September 2021
Debt Instrument, Redemption [Line Items]
Debt instrument stated interest rate (percent)	7.50%	7.50%
7 1/2% Senior Notes Maturing September 2021 | Debt Instrument, Redemption, Period One
Debt Instrument, Redemption [Line Items]
Debt Instrument, redemption price percentage	105.625%
7 1/2% Senior Notes Maturing September 2021 | Debt Instrument, Redemption, Period Two
Debt Instrument, Redemption [Line Items]
Debt Instrument, redemption price percentage	103.75%
7 1/2% Senior Notes Maturing September 2021 | Debt Instrument, Redemption, Period Three
Debt Instrument, Redemption [Line Items]
Debt Instrument, redemption price percentage	101.875%
7 1/2% Senior Notes Maturing September 2021 | Debt Instrument, Redemption, Period Four
Debt Instrument, Redemption [Line Items]
Debt Instrument, redemption price percentage	100.00%
8 3/4% Senior Notes Maturing March 2022
Debt Instrument, Redemption [Line Items]
Debt instrument stated interest rate (percent)	8.75%
8 3/4% Senior Notes Maturing March 2022 | Debt Instrument, Redemption, Period One
Debt Instrument, Redemption [Line Items]
Debt Instrument, redemption price percentage	100.00%
8 3/4% Senior Notes Maturing March 2022 | Debt Instrument, Redemption, Period Two
Debt Instrument, Redemption [Line Items]
Debt Instrument, redemption price percentage	104.375%
8 3/4% Senior Notes Maturing March 2022 | Debt Instrument, Redemption, Period Three
Debt Instrument, Redemption [Line Items]
Debt Instrument, redemption price percentage	102.188%
8 3/4% Senior Notes Maturing March 2022 | Debt Instrument, Redemption, Period Four
Debt Instrument, Redemption [Line Items]
Debt Instrument, redemption price percentage	100.00%
7 1/4% Senior Notes Maturing February 2023
Debt Instrument, Redemption [Line Items]
Debt instrument stated interest rate (percent)	7.25%	7.25%
7 1/4% Senior Notes Maturing February 2023 | Debt Instrument, Redemption, Period One
Debt Instrument, Redemption [Line Items]
Debt Instrument, redemption price percentage	100.00%
7 1/4% Senior Notes Maturing February 2023 | Debt Instrument, Redemption, Period Two
Debt Instrument, Redemption [Line Items]
Debt Instrument, redemption price percentage	103.625%
7 1/4% Senior Notes Maturing February 2023 | Debt Instrument, Redemption, Period Three
Debt Instrument, Redemption [Line Items]
Debt Instrument, redemption price percentage	102.41%
7 1/4% Senior Notes Maturing February 2023 | Debt Instrument, Redemption, Period Four
Debt Instrument, Redemption [Line Items]
Debt Instrument, redemption price percentage	101.208%
7 1/4% Senior Notes Maturing February 2023 | Debt Instrument, Redemption, Period Five [Member]
Debt Instrument, Redemption [Line Items]
Debt Instrument, redemption price percentage	100.00%