Long-term Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2011
Long-term debt
Debt instrument, face amount	$ 573,900		$ 599,800
Carrying amount of long-term debt, net of discount	562,330		592,458
Less current portion	(4,250)		0
Long-term debt, net	558,080		592,458
Senior secured term loan, due March 2022
Long-term debt
Debt instrument, face amount	423,938	$ 425,000
Carrying amount of long-term debt, net of discount	414,490		0
7.25% Senior notes, due January 2019
Long-term debt
Debt instrument, face amount	150,000		150,000	$ 150,000
Carrying amount of long-term debt, net of discount	$ 147,840		$ 147,192
Interest rate on long-term debt (as a percent)	7.25%		7.25%	7.25%
Senior Secured Notes 7.625 Percent
Long-term debt
Debt instrument, face amount			$ 400,000		$ 400,000
Carrying amount of long-term debt, net of discount	$ 0		$ 396,058
Interest rate on long-term debt (as a percent)			7.625%		7.625%
Convertible Senior Subordinated Notes 8.75 Percent Due 2016
Long-term debt
Debt instrument, face amount			$ 49,791
Carrying amount of long-term debt, net of discount	$ 0		$ 49,208
Interest rate on long-term debt (as a percent)		8.75%	8.75%