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 6 Months Ended
Mar. 31, 2018
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Debt Instrument [Line Items]          
Payment of Accrued Interest and Fees       $ 20,800  
Cash available for general corporate purposes       492,500  
Loss (gain) on extinguishment of debt   $ (473) $ 1,049 2,470 $ 1,049
5.625% Senior Notes Due 2026 [Member]          
Debt Instrument [Line Items]          
Face Amount $ 300,000        
Interest rate, stated percentage 5.625%        
2.5% Convertible Senior Notes Due 2023 [Member]          
Debt Instrument [Line Items]          
Face Amount $ 550,000 $ 550,000   $ 550,000  
Interest rate, stated percentage 2.50% 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       $ 246,300  
Repurchase Premium       $ 90,400