STOCK-BASED COMPENSATION (Stock Option Activity) (Details) - Stock Options - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Number of Options (in shares)
Options outstanding, beginning of period	4,082,944	4,901,748	6,637,239
Options granted	131,849	160,181	261,373
Options modified	17,871
Options exercised	(899,033)	(945,166)	(1,789,434)
Options forfeited/cancelled	(10,701)	(32,569)	(200,210)
Options expired		(1,250)	(7,220)
Options outstanding, end of period	3,322,930	4,082,944	4,901,748
Options vested and exercisable as of December 31, 2019	2,908,237
Options expected to vest as of December 31, 2019	392,241
Weighted Average Exercise Price (in dollars per share)
Options outstanding, beginning of period	$ 44.54	$ 40.91	$ 37.20
Options granted	169.13	112.81	73.40
Options modified	163.55
Options exercised	41.21	36.69	30.23
Options forfeited/cancelled	97.83	63.28	57.09
Options expired		25.72	4.63
Options outstanding, end of period	50.85	$ 44.54	$ 40.91
Options vested and exercisable as of December 31, 2019	41.53
Options expected to vest as of December 31, 2019	$ 115.26
Aggregate Intrinsic Value
Options outstanding, beginning of period	$ 291,846	$ 326,064	$ 179,936
Options outstanding, end of period	536,015	$ 291,846	$ 326,064
Options vested and exercisable as of December 31, 2019	496,226
Options expected to vest as of December 31, 2019	$ 38,010
Weighted Average Remaining Contractual Term (in years)
Options outstanding as of December 31, 2019	4 years 9 months 18 days
Options vested and exercisable as of December 31, 2019	4 years 3 months 18 days
Options expected to vest as of December 31, 2019	8 years 1 month 6 days