STOCK-BASED COMPENSATION - Stock Option Activity (Details) - Employee Stock Option $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2016 USD ($) $ / shares shares
Number of Options
Options outstanding at January 1, 2016 | shares	7,450,914
Options granted | shares	291,112
Options exercised | shares	(666,024)
Options forfeited/cancelled | shares	(158,486)
Options outstanding at June 30, 2016 | shares	6,917,516
Options vested and exercisable at June 30, 2016 | shares	3,536,211
Options expected to vest | shares	3,180,340
Weighted Average Exercise Price
Options outstanding at January 1, 2016 | $ / shares	$ 34.07
Options granted | $ / shares	70.58
Options exercised | $ / shares	18.92
Options forfeited/cancelled | $ / shares	46.05
Options outstanding at June 30, 2016 | $ / shares	36.79
Options vested and exercisable at June 30, 2016 | $ / shares	25.47
Options expected to vest | $ / shares	$ 48.26
Aggregate Intrinsic Value
Options outstanding at January 1, 2016 | $	$ 331,938
Options granted | $	(1,825)
Options exercised | $	(30,231)
Options forfeited/cancelled | $	(2,894)
Options outstanding at June 30, 2016 | $	190,370
Options vested and exercisable at June 30, 2016 | $	137,346
Options expected to vest | $	$ 51,044