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