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SHAREHOLDERS' EQUITY AND SHARE-BASED COMPENSATION - Stock option activity (Details) - USD ($)
$ / shares in Units, $ in Thousands
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Number of Options      
Outstanding at the beginning of the period (in shares) 3,163,125    
Granted (in shares) 144,654 900,000 100,000
Exercised (in shares) (1,173,132)    
Forfeited (in shares) (138,138)    
Outstanding at the end of the period (in shares) 1,996,509 3,163,125  
Exercisable at the end of the period (in shares) 1,225,924    
Weighted average exercise price      
Outstanding at the beginning of the period (in dollars per share) $ 20.13    
Granted (in dollars per share) 29.17 $ 24.21 $ 84.61
Exercised (in dollars per share) 9.63    
Forfeited (in dollars per share) 34.13    
Outstanding at the end of the period (in dollars per share) 25.98 $ 20.13  
Exercisable at the end of the period (in dollars per share) $ 21.00    
Weighted average contractual term      
Weighted average contractual term 5 years 3 months 26 days 4 years 11 months 9 days  
Exercisable at the end of the period 3 years 5 months 12 days    
Aggregate intrinsic value      
Aggregate intrinsic value (in dollars) $ 15,942 $ 35,842  
Exercisable at the end of the period (in dollars) $ 10,825