Quarterly report pursuant to Section 13 or 15(d)

LONG-TERM DEBT (Debt Additions and Repayments) (Details)

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LONG-TERM DEBT (Debt Additions and Repayments) (Details) - USD ($)
$ in Thousands
 1 Months Ended 3 Months Ended
Mar. 31, 2018
Mar. 31, 2018
Mar. 31, 2017
Debt Instrument [Line Items]      
Payment of Accrued Interest and Fees $ 20,900    
Cash available for general corporate purposes 523,900    
Loss on extinguishment of debt 2,900 $ 2,943 $ 0
5.625% Senior Notes Due 2026 [Member]      
Debt Instrument [Line Items]      
Face Amount $ 300,000 $ 300,000  
Interest rate, stated percentage 5.625% 5.625%  
2.5% Convertible Senior Notes Due 2023 [Member]      
Debt Instrument [Line Items]      
Face Amount $ 550,000 $ 550,000  
Interest rate, stated percentage 2.50% 2.50%  
5.625% Senior Notes Due 2026 & 2.5% Convertible Senior Notes Due 2023 [Member]      
Debt Instrument [Line Items]      
Proceeds from Issuance of Debt $ 850,000    
2.5% Convertible Senior Notes Due 2019 [Member]      
Debt Instrument [Line Items]      
Interest rate, stated percentage 2.50% 2.50%  
Extinguishment of Debt, Amount $ 223,300    
Repurchase Premium $ 81,900