SHAREHOLDERS' EQUITY AND SHARE-BASED COMPENSATION - Activity related to our stock options (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Number of Options
Outstanding at the beginning of the period (in shares)	2,601,892
Granted (in shares)	853,510	100,000	100,000
Exercised (in shares)	(130,682)
Forfeited (in shares)	(161,595)
Outstanding at the end of the period (in shares)	3,163,125	2,601,892
Exercisable at the end of the period (in shares)	2,214,051
Weighted average exercise price
Outstanding at the beginning of the period (in dollars per share)	$ 21.21
Granted (in dollars per share)	24.21	$ 84.61	$ 104.84
Exercised (in dollars per share)	10.64
Forfeited (in dollars per share)	66.72
Outstanding at the end of the period (in dollars per share)	20.13	$ 21.21
Exercisable at the end of the period (in dollars per share)	$ 14.43
Weighted average contractual term
Weighted average contractual term	4 years 11 months 9 days	4 years 5 months 8 days
Exercisable at the end of the period	3 years 1 month 13 days
Aggregate intrinsic value
Aggregate intrinsic value (in dollars)	$ 35,842	$ 47,805
Exercisable at the end of the period (in dollars)	$ 32,395