STOCK-BASED COMPENSATION - Stock Option Activity (Details) - Employee Stock Option $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($) $ / shares shares
Number of Options
Options outstanding at January 1, 2017 | shares	6,637,239
Options granted | shares	234,990
Options exercised | shares	(486,524)
Options forfeited/cancelled | shares	(75,456)
Options outstanding at March 31, 2017 | shares	6,310,249
Options vested and exercisable at March 31, 2017 | shares	4,302,714
Options expected to vest | shares	1,891,705
Weighted Average Exercise Price
Options outstanding at January 1, 2017 | $ / shares	$ 37.20
Options granted | $ / shares	73.27
Options exercised | $ / shares	27.92
Options forfeited/cancelled | $ / shares	57.87
Options outstanding at March 31, 2017 | $ / shares	39.06
Options vested and exercisable at March 31, 2017 | $ / shares	30.84
Options expected to vest | $ / shares	$ 56.33
Aggregate Intrinsic Value
Options outstanding at January 1, 2017 | $	$ 179,936
Options granted | $	529
Options exercised | $	(23,159)
Options forfeited/cancelled | $	(1,332)
Options outstanding at March 31, 2017 | $	230,072
Options vested and exercisable at March 31, 2017 | $	192,245
Options expected to vest | $	$ 36,302