Annual report pursuant to Section 13 and 15(d)

LONG-TERM DEBT (2.5% Convertible Senior Notes) (Details)

v3.8.0.1
LONG-TERM DEBT (2.5% Convertible Senior Notes) (Details) - 2.5% Convertible Senior Notes Due 2019 [Member]
$ / shares in Units, shares in Millions
12 Months Ended
Dec. 31, 2017
USD ($)
shares
Dec. 31, 2016
Dec. 31, 2015
May 19, 2014
$ / shares
Debt Instrument [Line Items]        
Face amount $ 275,000,000      
Interest rate, stated percentage 2.50% 2.50% 2.50%  
Conversion ratio 0.0288363      
Conversion premium 52.50%      
Last reported sale price used to calculate conversion premium | $ / shares       $ 22.74
Maximum number of shares issuable upon conversion | shares 7.9      
Carrying amount of equity component $ 22,000,000      
Debt discount amortization period 1 year      
Effective interest rate 5.00%      
Redemption, Defined Changes of Control [Member]        
Debt Instrument [Line Items]        
Redemption price, percentage 100.00%