STOCK-BASED COMPENSATION, Stock Option Activity (Details) - Jun. 30, 2015 - USD ($) $ / shares in Units, $ in Thousands	Total
Number of Options
Options outstanding at January 1, 2015	6,838,746
Options granted	2,083,700
Options exercised	(862,174)
Options forfeited/cancelled	(124,023)
Options outstanding at June 30, 2015	7,936,249
Options vested and exercisable at June 30, 2015	2,952,470
Options expected to vest	4,570,435
Weighted Average Exercise Price
Options outstanding at January 1, 2015	$ 20.98
Options granted	61.43
Options exercised	16.25
Options forfeited/cancelled	28.59
Options outstanding at June 30, 2015	31.99
Options vested and exercisable at June 30, 2015	15.01
Options expected to vest	$ 41.60
Aggregate Intrinsic Value
Options outstanding at January 1, 2015	$ 183,073
Options granted	20,420
Options exercised	(47,402)
Options forfeited/cancelled	(5,288)
Options outstanding at June 30, 2015	311,418
Options vested and exercisable at June 30, 2015	165,988
Options expected to vest	$ 135,422