LONG-TERM DEBT - Schedule of Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2017
Debt Instrument [Line Items]
Total	$ 1,694,541
Current amount of long-term debt	(5,488)	$ (16,377)
Deferred financing costs (excludes the revolving credit)	(14,409)	(18,082)
Total long-term debt, net of current debt	1,689,949	1,697,114
Outstanding standby letters of credit	6,229	5,862
7.250% senior unsecured notes, due November 1, 2024
Debt Instrument [Line Items]
Total debt before deferred financing costs	400,000	400,000
Plus unamortized premium	9,306	11,732
Total	409,306	411,732
6.500% notes, due May 1, 2027
Debt Instrument [Line Items]
Total debt before deferred financing costs	425,000	425,000
Plus unamortized premium	4,318	5,000
Total	429,318	430,000
Revolver
Debt Instrument [Line Items]
Plus unamortized premium	1,681	1,968
Total	870,414	888,968
Revolver | Revolver
Debt Instrument [Line Items]
Total debt before deferred financing costs	114,727	117,000
Revolver | Term B-2 Loan, due November 17, 2024
Debt Instrument [Line Items]
Total debt before deferred financing costs	$ 754,006	770,000
Senior Unsecured Debt | 7.250% senior unsecured notes, due November 1, 2024
Debt Instrument [Line Items]
Stated interest rate (percent)	7.25%		7.25%
Other Debt
Debt Instrument [Line Items]
Total	$ 808	873
Total Debt Before Financing Costs
Debt Instrument [Line Items]
Total	$ 1,709,846	$ 1,731,573