Long-term Debt (Details) - USD ($)	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Mar. 31, 2015	Feb. 28, 2015	Dec. 31, 2013
Long-term debt
Debt instrument, face amount	$ 568,100,000		$ 573,900,000
Carrying amount of long-term debt, net of discounts and debt issue costs	557,580,000		562,330,000
Less current portion	(4,250,000)		(4,250,000)
Long-term debt	553,330,000		558,080,000
Senior secured term loan, due March 2022
Long-term debt
Debt instrument, face amount	421,813,000		423,938,000	$ 425,000,000
Carrying amount of long-term debt, net of discounts and debt issue costs	413,115,000		414,490,000
7.25% Senior notes, due January 2019
Long-term debt
Debt instrument, face amount	146,250,000		150,000,000			$ 150,000,000
Carrying amount of long-term debt, net of discounts and debt issue costs	$ 144,465,000		$ 147,840,000
Interest rate on long-term debt (as a percent)	7.25%	7.25%	7.25%			7.25%
Convertible Senior Subordinated Notes 8.75 Percent Due 2016
Long-term debt
Interest rate on long-term debt (as a percent)					8.75%