Annual report pursuant to Section 13 and 15(d)

FAIR VALUE MEASUREMENTS (Fair Value of Debt) (Details)

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FAIR VALUE MEASUREMENTS (Fair Value of Debt) (Details) - Level 2 [Member] - USD ($)
$ in Thousands
Dec. 31, 2018
Dec. 31, 2017
4.875% Senior Notes Due 2024 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term Debt, Fair Value $ 552,368 $ 592,325
5.625% Senior Notes Due 2026 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term Debt, Fair Value 302,097 0
5.375% Senior Notes due 2022 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term Debt, Fair Value 251,390 259,233
2.5% Convertible Senior Notes Due 2023 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Convertible Debt, Fair Value Disclosures 561,699 0
2.5% Convertible Senior Notes Due 2019 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Convertible Debt, Fair Value Disclosures $ 40,710 $ 310,635