STOCK-BASED COMPENSATION - Stock Option Activity (Details) - Employee Stock Option $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2016 USD ($) $ / shares shares
Number of Options
Options outstanding at January 1, 2016 | shares	7,450,914
Options granted | shares	284,383
Options exercised | shares	(354,341)
Options forfeited/cancelled | shares	(47,700)
Options outstanding at March 31, 2016 | shares	7,333,256
Options vested and exercisable at March 31, 2016 | shares	3,829,718
Options expected to vest | shares	3,273,437
Weighted Average Exercise Price
Options outstanding at January 1, 2016 | $ / shares	$ 34.07
Options granted | $ / shares	70.50
Options exercised | $ / shares	12.30
Options forfeited/cancelled | $ / shares	47.96
Options outstanding at March 31, 2016 | $ / shares	36.45
Options vested and exercisable at March 31, 2016 | $ / shares	25.43
Options expected to vest | $ / shares	$ 48.11
Aggregate Intrinsic Value
Options outstanding at January 1, 2016 | $	$ 331,938
Options granted | $	1,186
Options exercised | $	(22,100)
Options forfeited/cancelled | $	(1,274)
Options outstanding at March 31, 2016 | $	280,277
Options vested and exercisable at March 31, 2016 | $	188,575
Options expected to vest | $	$ 86,942