Long-term Debt - Interest and Debt Maturities (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended	9 Months Ended
	Jun. 30, 2016	Jun. 30, 2016	Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2016	Jun. 30, 2015	Sep. 30, 2015	Sep. 30, 2011
Long-term debt
Interest expense		$ 9,400	$ 8,200		$ 26,200	$ 56,500
Non-cash interest expense		$ 600	$ 600		$ 1,745	$ 5,611
Weighted average interest rate (as a percent)	4.80%	4.80%			4.80%		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
Decrease in annual interest rate	0.50%
Required quarterly repayments due					$ 1,100