STOCK-BASED COMPENSATION (Stock Option Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Number of Options (in shares)
Options outstanding, beginning of period	6,838,746	5,823,536	6,296,709
Options granted	2,219,725	2,400,500	1,987,952
Options exercised	(1,405,826)	(1,171,097)	(2,156,898)
Options forfeited/cancelled	(201,731)	(214,193)	(304,227)
Options outstanding, end of period	7,450,914	6,838,746	5,823,536
Options vested and exercisable at December 31, 2015	2,446,226
Options expected to vest	4,690,899
Weighted Average Exercise Price (in dollars per share)
Options outstanding, beginning of period	$ 20.98	$ 13.99	$ 7.51
Options granted	62.18	32.51	23.60
Options exercised	14.70	9.05	4.31
Options forfeited/cancelled	34.48	25.33	11.50
Options outstanding, end of period	34.07	$ 20.98	$ 13.99
Options vested and exercisable at December 31, 2015	15.95
Options expected to vest	$ 42.51
Aggregate Intrinsic Value
Options outstanding, beginning of period	$ 183,073	$ 122,003	$ 66,682
Options granted	36,492	36,584	22,543
Options exercised	(89,860)	(45,321)	(66,066)
Options forfeited/cancelled	(8,904)	(4,802)	(7,131)
Options outstanding, end of period	331,938	$ 183,073	$ 122,003
Options vested and exercisable at December 31, 2015	153,305
Options expected to vest	$ 169,388