STOCK PLANS AND SHARE-BASED COMPENSATION (Tables)

3 Months Ended

Mar. 31, 2015

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock-based Compensation Expense

The following table summarizes the stock-based compensation expense recognized in accordance with ASC 718-10 for the three months ended March 31, 2015, and March 31, 2014 (in thousands).

	Three Months Ended
	March 31,
	2015		2014
Cost of revenues	$	249	$	219
Research and development	1,391		1,212
Sales and marketing	1,012		935
General and administrative	1,739		1,549
Total stock-based compensation expense	$	4,391	$	3,915

Schedule of Unrecognized Compensation Expense for Unvested Awards

The following table summarizes total compensation expense related to unvested awards not yet recognized, net of expected forfeitures, and the weighted-average period over which it is expected to be recognized as of March 31, 2015.

	March 31, 2015
	Unrecognized Compensation Expense for Unvested Awards			Weighted Average Remaining Recognition Period
	(In thousands)			(In years)
Options		$	587		0.94
Performance-based awards		1,256			0.75
Long-term performance-based awards		3,879			2.26
Restricted stock units		22,379			2.29
Purchase plan		434			0.50
Total unrecognized compensation expense		$	28,535

Schedule of Share-based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions

The fair value of employees’ stock purchase rights under the Purchase Plan was estimated using the Black-Scholes model with the following weighted-average assumptions:        

	Three Months Ended
	March 31,
	2015	2014
Risk-free interest rates	0.07%	0.07%
Expected volatility rates	34%	30%
Expected dividend yield	0.89%	0.66%
Expected term of purchase right (in years)	0.5	0.5
Weighted-average estimated fair value of purchase rights	$12.89	$13.31

Summary of Option Activity Under the Plans

A summary of stock option activity under the Plans, excluding performance-based awards and restricted stock units, as of March 31, 2015, and changes during the three months then ended, is presented below:

	Shares (in thousands)		Weighted- Average Exercise Price	Weighted-Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding at January 1, 2015	1,344		$27.27
Granted	—		—
Exercised	(49	)	$21.24
Forfeited or expired	—		—
Outstanding at March 31, 2015	1,295		$27.49	3.42	$	31,846
Exercisable at March 31, 2015	1,256		$27.05	3.31	$	31,453
Vested and expected to vest at March 31, 2015	1,294		$27.48	3.42	$	31,837

Performance Based Awards (PSUs) [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Schedule of Share-based Compensation, Restricted Stock Units Award Activity

A summary of performance-based awards outstanding as of March 31, 2015, and activity during the three months then ended, is presented below:

	Shares (in thousands)	Weighted- Average Grant Date Fair Value Per Share	Weighted-Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding at January 1, 2015	—	—
Granted	50	$53.74
Vested	—	—
Change in units due to performance achievement for PSUs vested in the year	—	—
Forfeited or expired	—	—
Outstanding at March 31, 2015	50	$53.74	0.75	$	2,614
Outstanding and expected to vest at March 31, 2015	30		0.75	$	1,569

Long-Term Performance-based Awards (PRSUs) [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Schedule of Share-based Compensation, Restricted Stock Units Award Activity

A summary of long-term performance-based awards outstanding as of March 31, 2015, and activity during the three months then ended, is presented below:

	Shares (in thousands)	Weighted- Average Grant Date Fair Value Per Share	Weighted-Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding at January 1, 2015	61	$55.51
Granted	65	$52.80
Vested	—	—
Forfeited or expired	—	—
Outstanding at March 31, 2015	126	$54.12	2.26	$	6,546
Outstanding and expected to vest at March 31, 2015	102		2.25	$	5,305

Restricted Stock Units (RSUs) [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Schedule of Share-based Compensation, Restricted Stock Units Award Activity

A summary of RSUs outstanding as of March 31, 2015, and changes during the three months then ended, are as follows:

	Shares (in thousands)		Weighted- Average Grant Date Fair Value Per Share	Weighted-Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding at January 1, 2015	692		$43.86
Granted	104		$52.25
Vested	(64	)	$42.70
Forfeited or expired	(3	)	$41.23
Outstanding at March 31, 2015	729		$45.16	1.45	$	37,987
Outstanding and expected to vest at March 31, 2015	682			1.26	$	35,544