STOCKHOLDERS' EQUITY (Schedule of Stock Option Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Number of Shares
Outstanding, beginning balance (in shares)	8,018,941
Granted (in shares)	920,850
Exercised (in shares)	(1,216,110)
Canceled (in shares)	(210,770)
Outstanding, ending balance (in shares)	7,512,911	8,018,941
Options vested and exercisable (in shares)	5,904,796
Weighted- Average Exercise Price
Outstanding, beginning balance (in USD per share)	$ 21.71
Granted (in USD per share)	34.60
Exercised (in USD per share)	19.85
Canceled (in USD per share)	47.08
Outstanding, ending balance (in USD per share)	22.88	$ 21.71
Options vested and exercisable (in USD per share)	$ 20.32
Weighted- Average Remaining Contractual Term
Outstanding, Weighted-Average Remaining Contractual Term (in years)	5 years 10 months 6 days	6 years 1 month 6 days
Options vested and exercisable, Weighted-Average Remaining Contractual Term (in years)	5 years 18 days
Aggregate Intrinsic Value
Outstanding, Aggregate Intrinsic Value	$ 162,770	$ 147,673
Options vested and exercisable, Aggregate Intrinsic Value	$ 143,342