STOCK-BASED COMPENSATION (Stock Option Activity) (Details) - Stock Options - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Number of Options (in shares)
Options outstanding, beginning of period	7,450,914	6,838,746	5,823,536
Options granted	313,088	2,219,725	2,400,500
Options exercised	(895,804)	(1,405,826)	(1,171,097)
Options forfeited/cancelled	(227,759)	(201,731)	(214,193)
Options expired	(3,200)
Options outstanding, end of period	6,637,239	7,450,914	6,838,746
Options vested and exercisable at December 31, 2016	3,350,682
Options expected to vest	3,127,635
Weighted Average Exercise Price (in dollars per share)
Options outstanding, beginning of period	$ 34.07	$ 20.98	$ 13.99
Options granted	70.27	62.18	32.51
Options exercised	20.13	14.70	9.05
Options forfeited/cancelled	47.89	34.48	25.33
Options expired	1.52
Options outstanding, end of period	37.20	$ 34.07	$ 20.98
Options vested and exercisable at December 31, 2016	25.96
Options expected to vest	$ 48.28
Aggregate Intrinsic Value
Options outstanding, beginning of period	$ 331,938	$ 183,073	$ 122,003
Options granted	(1,866)	36,492	36,584
Options exercised	(39,577)	(89,860)	(45,321)
Options forfeited/cancelled	(3,740)	(8,904)	(4,802)
Options expired	(201)
Options outstanding, end of period	179,936	$ 331,938	$ 183,073
Options vested and exercisable at December 31, 2016	128,499
Options expected to vest	$ 50,136