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 $)
 1 Months Ended 6 Months Ended 1 Months Ended
May 31, 2014
Jun. 30, 2014
Jun. 30, 2013
May 31, 2014
2.5% Convertible Senior Notes Due 2019 [Member]
Jun. 30, 2014
2.5% Convertible Senior Notes Due 2019 [Member]
Jun. 30, 2014
5.375% Senior Notes due 2022 [Member]
May 31, 2014
5.375% Senior Notes due 2022 [Member]
Jun. 30, 2014
2.875% Convertible Senior Notes Due 2027 [Member]
Dec. 31, 2013
2.875% Convertible Senior Notes Due 2027 [Member]
Jun. 30, 2013
2.875% Convertible Senior Notes Due 2027 [Member]
Debt Instrument [Line Items]                    
Face amount       $ 275,000,000 $ 275,000,000   $ 250,000,000      
Interest rate, stated percentage       2.50% 2.50% 5.375% 5.375% 2.875% 2.875% 2.875%
Conversion ratio       0.0288363            
Related fees and expenses 10,400,000                  
Proceeds from long-term debt, net of debt issuance costs $ 514,600,000 $ 514,612,000 $ 89,369,000