STOCK-BASED COMPENSATION, Stock Option Activity (Details) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended
	Sep. 30, 2014
Number of Options
Options outstanding at January 1, 2014	5,823,536
Options granted	2,373,500
Options exercised	(828,756)
Options forfeited/cancelled	(162,829)
Options outstanding at September 30, 2014	7,205,451
Options vested and exercisable at September 30, 2014	2,708,228
Options expected to vest	4,101,056
Weighted Average Exercise Price
Options outstanding at January 1, 2014	$ 13.99
Options granted	$ 32.33
Options exercised	$ 8.54
Options forfeited/cancelled	$ 24.41
Options outstanding at September 30, 2014	$ 20.42
Options vested and exercisable at September 30, 2014	$ 9.87
Options expected to vest	$ 26.58
Aggregate Intrinsic Value
Options outstanding at January 1, 2014	$ 122,003
Options granted	27,200
Options exercised	(29,214)
Options forfeited/cancelled	(3,156)
Options outstanding at September 30, 2014	168,391
Options vested and exercisable at September 30, 2014	91,863
Options expected to vest	$ 70,579