Long-term Debt - Debt Summary (Details) - USD ($)	Dec. 31, 2017	Mar. 31, 2017	Jan. 19, 2017	Dec. 31, 2016
Long-term Debt
Long-term debt	$ 1,280,201,000			$ 1,432,689,000
Less current maturities of long-term debt	(35,612,000)			(85,595,000)
Less debt issuance costs	(27,406,000)			(16,535,000)
Long-term debt, net of current maturities and debt issuance costs	1,214,625,000			1,329,939,000
Senior Secured Credit Facility
Long-term Debt
Long-term debt	760,000,000			976,845,000
Term Loan B Facility
Long-term Debt
Less discount on senior secured credit facility Term Loan B	(2,558,000)			(620,000)
Senior Subordinated Notes, 5.875 Percent, Due November 2021
Long-term Debt
Long-term debt				300,000,000
Principal amount				$ 300,000,000
Interest rate (as a percent)		5.875%		5.875%
Senior Unsecured Notes 5.625 Percent Due January 15, 2027
Long-term Debt
Long-term debt	400,000,000
Principal amount	$ 400,000,000		$ 400,000,000
Interest rate (as a percent)	5.625%		5.625%
Other long-term obligations
Long-term Debt
Long-term debt	$ 119,310,000			$ 154,084,000
Capital leases
Long-term Debt
Long-term debt	$ 891,000			$ 1,760,000