Long-term Debt - Interest and Debt Maturities (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015	Sep. 30, 2015	Sep. 30, 2011
Long-term debt
Interest expense	$ 8,300	$ 36,100	$ 16,700	$ 48,300
Non-cash interest expense	$ 600	$ 4,500	$ 1,184	5,042
Weighted average interest rate (as a percent)	5.20%		5.20%		5.20%
Senior Secured Notes 7.625 Percent
Long-term debt
Interest expense				$ 21,300
Interest rate on secured notes (as a percent)	7.625%	7.625%	7.625%	7.625%		7.625%
Senior secured term loan, due March 2022
Long-term debt
Required quarterly repayments due			$ 1,100