STOCK-BASED COMPENSATION, Stock Option Activity (Details) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2015 USD ($) $ / shares shares
Number of Options
Options outstanding at January 1, 2015	6,838,746
Options granted	2,189,424
Options exercised	(1,086,066)
Options forfeited/cancelled	(171,222)
Options outstanding at September 30, 2015	7,770,882
Options vested and exercisable at September 30, 2015	2,753,236
Options expected to vest	4,634,538
Weighted Average Exercise Price
Options outstanding at January 1, 2015 | $ / shares	$ 20.98
Options granted | $ / shares	62.03
Options exercised | $ / shares	16.28
Options forfeited/cancelled | $ / shares	33.32
Options outstanding at September 30, 2015 | $ / shares	32.93
Options vested and exercisable at September 30, 2015 | $ / shares	15.08
Options expected to vest | $ / shares	$ 42.26
Aggregate Intrinsic Value
Options outstanding at January 1, 2015 | $	$ 183,073
Options granted | $	27,346
Options exercised | $	(63,252)
Options forfeited/cancelled | $	(7,054)
Options outstanding at September 30, 2015 | $	323,191
Options vested and exercisable at September 30, 2015 | $	163,652
Options expected to vest | $	$ 149,510