STOCK PLANS AND SHARE-BASED COMPENSATION (Stock-Based Compensation) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Stock-based compensation expense for stock options, stock awards and employee stock purchases included in operations:
Stock-based compensation expense	$ 4,328	$ 3,642	$ 7,964	$ 6,673
Unrecognized Compensation Expense for Unvested Awards	27,605		27,605
Cost of revenues [Member]
Stock-based compensation expense for stock options, stock awards and employee stock purchases included in operations:
Stock-based compensation expense	264	256	528	501
Research and development [Member]
Stock-based compensation expense for stock options, stock awards and employee stock purchases included in operations:
Stock-based compensation expense	1,640	1,566	2,746	2,687
Sales and marketing [Member]
Stock-based compensation expense for stock options, stock awards and employee stock purchases included in operations:
Stock-based compensation expense	795	746	1,624	1,493
General and administrative [Member]
Stock-based compensation expense for stock options, stock awards and employee stock purchases included in operations:
Stock-based compensation expense	1,629	1,074	3,066	1,992
Stock Options [Member]
Stock-based compensation expense for stock options, stock awards and employee stock purchases included in operations:
Stock-based compensation expense	700	900	1,700	1,900
Unrecognized Compensation Expense for Unvested Awards	2,569		2,569
Weighted Average Remaining Recognition Period (in years)	1 year 10 months 17 days
Performance Based Awards [Member]
Stock-based compensation expense for stock options, stock awards and employee stock purchases included in operations:
Stock-based compensation expense	900	700	1,300	1,100
Unrecognized Compensation Expense for Unvested Awards	2,013		2,013
Weighted Average Remaining Recognition Period (in years)	6 months
Restricted Stock Units (RSUs) [Member]
Stock-based compensation expense for stock options, stock awards and employee stock purchases included in operations:
Stock-based compensation expense	2,400	1,700	4,400	3,100
Unrecognized Compensation Expense for Unvested Awards	22,927		22,927
Weighted Average Remaining Recognition Period (in years)	2 years 11 months 12 days
Employee Stock [Member]
Stock-based compensation expense for stock options, stock awards and employee stock purchases included in operations:
Stock-based compensation expense	300	300	600	600
Unrecognized Compensation Expense for Unvested Awards	$ 96		$ 96
Weighted Average Remaining Recognition Period (in years)	6 months