STOCK-BASED COMPENSATION (Stock Options Activity) (Details) - Employee Stock Option $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($) $ / shares shares
Number of Options
Options outstanding at January 1, 2019 | shares	4,082,944
Options granted | shares	131,849
Options modified | shares	17,871
Options exercised | shares	(323,464)
Options forfeited/cancelled | shares	(2,624)
Options outstanding at March 31, 2019 | shares	3,906,576
Options vested and exercisable at March 31, 2019 | shares	3,422,907
Options expected to vest at March 31, 2019 | shares	445,175
Weighted Average Exercise Price
Options outstanding at January 1, 2019 | $ / shares	$ 44.54
Options granted | $ / shares	169.13
Options modified | $ / shares	163.55
Options exercised | $ / shares	36.76
Options forfeited/cancelled | $ / shares	61.38
Options outstanding at March 31, 2019 | $ / shares	49.92
Options vested and exercisable at March 31, 2019 | $ / shares	41.11
Options expected to vest at March 31, 2019 | $ / shares	$ 111.17
Aggregate Intrinsic Value
Options outstanding at March 31, 2019 | $	$ 465,698
Options vested and exercisable at March 31, 2019 | $	438,196
Options expected to vest at March 31, 2019 | $	$ 25,804
Weighted Average Remaining Contractual Term (in years)
Options outstanding at March 31, 2019	5 years 5 months 9 days
Options vested and exercisable at March 31, 2019	4 years 11 months 26 days
Options expected to vest at March 31, 2019	8 years 7 months 14 days