STOCK-BASED COMPENSATION (Details 2) - Options [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Option Shares
Outstanding at the beginning of the period (in shares)	578	474	458
Granted (in shares)	207	265	138
Exercised (in shares)	(13)	(127)	(89)
Forfeited (in shares)	(5)	(32)	(33)
Expired (in shares)	0	(2)	0
Outstanding at the end of the period (in shares)	767	578	474	458
Exercisable at the end of the period (in shares)	308
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 39.28	$ 29.40	$ 14.44
Granted (in dollars per share)	51.66	45.60	62.07
Exercised (in dollars per share)	15.92	11.79	9.24
Forfeited (in dollars per share)	53.29	47.84	11.81
Expired (in dollars per share)	0	139.32	0
Outstanding at the end of the period (in dollars per share)	42.93	39.28	29.40	$ 14.44
Exercisable at the end of the period (in dollars per share)	32.94
Weighted Average Grant-date Fair Value
Granted (in dollars per share)	$ 27.04	$ 22.45	$ 30.08
Weighted Average Remaining Term (years)
Outstanding at the end of the period weighted average remaining term	7 years 9 months 18 days	8 years 2 months 12 days	8 years 2 months 12 days	8 years 8 months 12 days
Exercisable at the end of the period weighted average remaining term	6 years 7 months 6 days
Aggregate Intrinsic Value
Outstanding at the beginning of the period intrinsic value (in dollars)	$ 12,928	$ 10,136	$ 19,472
Exercised at the end of the period intrinsic value (in dollars)	542	5,837	3,937
Outstanding at the end of the period intrinsic value (in dollars)	16,785	$ 12,928	$ 10,136	$ 19,472
Exercisable at the end of the period intrinsic value (in dollars)	$ 9,901