STOCK-BASED COMPENSATION (Stock Options Activity) (Details) - Employee Stock Option - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2019
Number of Options
Options outstanding at January 1, 2019	4,082,944
Options granted	131,849
Options modified	17,871
Options exercised	(528,572)
Options forfeited/cancelled	(2,624)
Options outstanding at June 30, 2019	3,701,468
Options vested and exercisable at June 30, 2019	3,232,985
Options expected to vest at June 30, 2019	435,976
Weighted Average Exercise Price
Options outstanding at January 1, 2019	$ 44.54
Options granted	169.13
Options modified	163.55
Options exercised	42.52
Options forfeited/cancelled	61.38
Options outstanding at June 30, 2019	49.83
Options vested and exercisable at June 30, 2019	40.60
Options expected to vest at June 30, 2019	$ 112.48
Aggregate Intrinsic Value
Options outstanding at June 30, 2019	$ 456,287
Options vested and exercisable at June 30, 2019	428,366
Options expected to vest at June 30, 2019	$ 26,427
Weighted Average Remaining Contractual Term (in years)
Options outstanding at June 30, 2019	5 years 2 months 12 days
Options vested and exercisable at June 30, 2019	4 years 8 months 12 days
Options expected to vest at June 30, 2019	8 years 4 months 24 days