STOCK-BASED COMPENSATION (Stock Option Activity) (Details) - Stock Options - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Number of Options (in shares)
Options outstanding, beginning of period	6,637,239	7,450,914	6,838,746
Options granted	261,373	313,088	2,219,725
Options exercised	(1,789,434)	(895,804)	(1,405,826)
Options forfeited/cancelled	(200,210)	(227,759)	(201,731)
Options expired	(7,220)	(3,200)
Options outstanding, end of period	4,901,748	6,637,239	7,450,914
Options vested and exercisable at December 31, 2017	3,068,917
Options expected to vest	1,764,538
Weighted Average Exercise Price (in dollars per share)
Options outstanding, beginning of period	$ 37.20	$ 34.07	$ 20.98
Options granted	73.40	70.27	62.18
Options exercised	30.23	20.13	14.70
Options forfeited/cancelled	57.09	47.89	34.48
Options expired	4.63	1.52
Options outstanding, end of period	40.91	$ 37.20	$ 34.07
Options vested and exercisable at December 31, 2017	31.49
Options expected to vest	$ 56.35
Aggregate Intrinsic Value
Options outstanding, beginning of period	$ 179,936	$ 331,938	$ 183,073
Options outstanding, end of period	326,064	$ 179,936	$ 331,938
Options vested and exercisable at December 31, 2017	233,054
Options expected to vest	$ 90,133
Weighted Average Remaining Contractual Term (in years)
Options outstanding at December 31, 2017	6 years 2 months 11 days
Options vested and exercisable at December 31, 2017	5 years 6 months 6 days
Options expected to vest	7 years 3 months 29 days