Quarterly report pursuant to Section 13 or 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
Sep. 30, 2018
Dec. 31, 2017
4.875% Senior Notes Due 2024 [Member]    
Debt Fair Value [Line Items]    
Estimated fair values of senior notes $ 565,967 $ 592,325
5.625% Senior Notes Due 2026 [Member]    
Debt Fair Value [Line Items]    
Estimated fair values of senior notes 303,408 0
5.375% Senior Notes due 2022 [Member]    
Debt Fair Value [Line Items]    
Estimated fair values of senior notes 254,043 259,233
2.5% Convertible Senior Notes Due 2023 [Member]    
Debt Fair Value [Line Items]    
Estimated fair values of convertible senior notes 600,875 0
2.5% Convertible Senior Notes Due 2019 [Member]    
Debt Fair Value [Line Items]    
Estimated fair values of convertible senior notes $ 45,182 $ 310,635