FINANCING ARRANGEMENTS (Summary of Financing Arrangements) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Current portion of long-term debt	$ 7,535	$ 7,535
Long-term debt, at par	1,564,626	1,572,162
Unamortized debt issuance costs and premium, net	(14,985)	(18,046)
Long-term debt, at carrying value	1,549,641	1,554,116
Secured debt | Secured senior Term Loans due June 30, 2024
Debt Instrument [Line Items]
Current portion of long-term debt	7,535	7,535
Long-term debt, at par	719,626	727,162
Unsecured debt | Unsecured senior notes, at 4.875%, due July 15, 2027 ("2027 Notes")
Debt Instrument [Line Items]
Long-term debt, at par	$ 545,000	545,000
Interest rate (as a percent)	4.875%
Unsecured debt | Unsecured senior notes, at 5.125%, due July 15, 2029 ("2029 Notes")
Debt Instrument [Line Items]
Long-term debt, at par	$ 300,000	$ 300,000
Interest rate (as a percent)	5.125%