STOCKHOLDERS' EQUITY (Schedule of Stock Option Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Number of Shares
Outstanding, beginning balance (in shares)	8,018,941
Granted (in shares)	920,850
Exercised (in shares)	(1,519,771)
Canceled (in shares)	(341,088)
Outstanding, ending balance (in shares)	7,078,932	8,018,941
Options vested and exercisable (in shares)	5,774,043
Weighted- Average Exercise Price
Outstanding, beginning balance (in dollars per share)	$ 21.71
Granted (in dollars per share)	34.60
Exercised (in dollars per share)	19.74
Canceled (in dollars per share)	44.78
Outstanding, ending balance (in dollars per share)	22.70	$ 21.71
Options vested and exercisable (in dollars per share)	$ 20.55
Weighted- Average Remaining Contractual Term
Outstanding, Weighted-Average Remaining Contractual Term (in years)	5 years 6 months 22 days	6 years 1 month 6 days
Options vested and exercisable, Weighted-Average Remaining Contractual Term (in years)	4 years 10 months 13 days
Aggregate Intrinsic Value
Outstanding, Aggregate Intrinsic Value	$ 145,613	$ 147,673
Options vested and exercisable, Aggregate Intrinsic Value	$ 131,625