STOCK-BASED COMPENSATION (Stock Option Activity) (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) $ / shares shares
Stock Options (Number of shares)
Outstanding, beginning balance (in shares) | shares	1,423,660
Granted (in shares) | shares	221,740
Exercised (in shares) | shares	(160,200)
Forfeited (in shares) | shares	(43,315)
Expired (in shares) | shares	(675)
Outstanding, ending balance (in shares) | shares	1,441,210
Vested and expected to vest (in shares) | shares	1,384,830
Exercisable (in shares) | shares	953,780
Stock Options (Weighted-average exercise price)
Weighted- average exercise price per share beginning balance (in dollars per share) | $ / shares	$ 46.56
Granted (in dollars per share) | $ / shares	91.23
Exercised (in dollars per share) | $ / shares	44.73
Forfeited (in dollars per share) | $ / shares	77.31
Expired (in dollars per share) | $ / shares	72.10
Weighted- average exercise price per share ending balance (in dollars per share) | $ / shares	52.70
Weighted- average exercise price per share, Vested and Expected to Vest (in dollars per share) | $ / shares	51.34
Weighted- average exercise price per share, Exercisable (in dollars per share) | $ / shares	$ 38.08
Weighted-average remaining contractual terms (years), Outstanding	5 years 7 months 13 days
Weighted-average remaining contractual terms (years), Vested and Expected to Vest	5 years 6 months
Weighted-average remaining contractual terms (years), Exercisable	4 years 3 months 22 days
Aggregate intrinsic value, Outstanding | $	$ 49,696
Aggregate intrinsic value, Vested and Expected to Vest | $	49,504
Aggregate intrinsic value, Exercisable | $	$ 46,103