STOCK PLANS AND SHARE BASED COMPENSATION (Tables)

12 Months Ended

Dec. 31, 2021

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

Stock-based Compensation Expense

The following table summarizes the stock-based compensation expense recognized in accordance with ASC 718-10 for the years ended December 31, 2021, 2020 and 2019:

	Year Ended December 31,
(In thousands)	2021		2020		2019
Cost of revenues	$	2,359	$	1,963	$	1,237
Research and development		12,127		10,378		8,423
Sales and marketing		7,630		6,290		5,015
General and administrative		15,493		12,281		8,672
Total stock-based compensation expense	$	37,609	$	30,912	$	23,347

Share-based Payment Arrangement, Nonvested Award, Cost

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 December 31, 2021:

	Unrecognized Compensation		Weighted Average
	Expense for Unvested		Remaining Recognition
	Awards		Period
	(In thousands)		(In years)
Long-term performance-based awards	$	7,474	1.19
Restricted stock units		35,707	2.26
Purchase plan		174	0.08
Total unrecognized compensation expense	$	43,355

Fair value assumptions for employees' stock purchase rights under the Purchase Plan

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 used during the three years ended December 31, 2021, 2020 and 2019:

	Year Ended December 31,
	2021			2020			2019
Risk-free interest rates		0.07	%		0.90	%		2.28	%
Expected volatility rates		41	%		47	%		37	%
Expected dividend yield		0.57	%		0.78	%		0.91	%
Expected term of purchase rights (in years)		0.50			0.50			0.50
Weighted-average estimated fair value of purchase rights	$	23.92		$	15.73		$	19.39

Summary of Option Activity Under the Plans

A summary of stock options outstanding as of December 31, 2021, and activity during three years then ended, is presented below:

				Weighted-
		Weighted-		Average
		Average		Remaining	Aggregate
	Shares	Exercise		Contractual Term	Intrinsic Value
	(In thousands)	Price		(In years)	(In thousands)
Outstanding at January 1, 2019	670	$	16.21
Granted	—		—
Exercised	(335)	$	12.98
Forfeited or expired	—		—
Outstanding at December 31, 2019	335	$	19.44
Granted	—		—
Exercised	(243)	$	18.99
Forfeited or expired	—		—
Outstanding at December 31, 2020	92	$	20.63
Granted	—		—
Exercised	(80)	$	20.50
Forfeited or expired	—		—
Outstanding at December 31, 2021	12	$	21.44	0.35	$	857
Vested and Exercisable at December 31, 2021	12			0.35	$	857

Summary of stock options outstanding by exercise price range

The following table summarizes the stock options outstanding at December 31, 2021:

	Options Outstanding				Options Exercisable
		Weighted Average	Weighted			Weighted
		Remaining	Average			Average
(Shares in thousands)	Options	Contractual Term	Exercise		Options	Exercise
Range of Exercise Prices	Outstanding	(In years)	Price		Exercisable	Price
$21.44 - $21.44	12	0.35	$	21.44	12	$	21.44

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

A summary of RSU awards outstanding as of December 31, 2021, and activity during the three years then ended, is presented below:

				Weighted-Average	Aggregate
		Weighted-Average		Remaining	Intrinsic
	Shares	Grant Date Fair		Contractual Term	Value
	(In thousands)	Value Per Share		(In years)	(In thousands)
Outstanding at January 1, 2019	1,790	$	29.10
Granted	582	$	34.90
Vested	(603)	$	28.10
Forfeited	(50)	$	31.72
Outstanding at December 31, 2019	1,719	$	31.33
Granted	439	$	44.82
Vested	(599)	$	30.25
Forfeited	(41)	$	36.77
Outstanding at December 31, 2020	1,518	$	35.51
Granted	271	$	83.79
Vested	(546)	$	35.03
Forfeited	(99)	$	39.85
Outstanding at December 31, 2021	1,144	$	46.81	1.25	$	106,306
Outstanding and expected to vest at December 31, 2021	1,081			1.20	$	100,433

Performance Based Awards [Member]

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

Summary of performance-based awards outstanding

A summary of PSU awards outstanding as of December 31, 2021, and activity during the three years then ended, is presented below:

				Weighted-
		Weighted-		Average
		Average		Remaining	Aggregate
	Shares	Grant Date Fair		Contractual Term	Intrinsic Value
	(In thousands)	Value Per Share		(In years)	(In thousands)
Outstanding at January 1, 2019	52	$	31.44
Granted	185	$	35.06
Vested	(52)	$	31.44
Forfeited or canceled	(64)	$	35.06
Outstanding at December 31, 2019	121	$	35.06
Granted	150	$	46.31
Vested	(121)	$	35.06
Forfeited or canceled	—		—
Outstanding at December 31, 2020	150	$	46.27
Granted	105	$	84.48
Vested	(150)	$	46.27
Forfeited or canceled	(1)	$	85.01
Outstanding at December 31, 2021	104	$	84.47	—	$	9,701
Outstanding and expected to vest at December 31, 2021	104			—	$	9,701

Long-Term Performance-Based Awards (PRSUs)

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

Summary of performance-based awards outstanding

A summary of PRSU awards outstanding as of December 31, 2021, and activity during the three years then ended, is presented below:

				Weighted-Average	Aggregate
		Weighted-Average		Remaining	Intrinsic
	Shares	Grant Date Fair		Contractual Term	Value
	(In thousands)	Value Per Share		(In years)	(In thousands)
Outstanding at January 1, 2019	426	$	27.74
Granted	144	$	34.09
Vested	(140)	$	21.63
Forfeited or canceled	(143)	$	31.50
Outstanding at December 31, 2019	287	$	32.03
Granted	152	$	49.67
Vested	—		—
Forfeited or canceled	(138)	$	29.95
Outstanding at December 31, 2020	301	$	41.90
Granted	103	$	82.92
Vested	(6)	$	29.94
Forfeited or canceled	(15)	$	40.05
Outstanding at December 31, 2021	383	$	53.14	0.92	$	35,537
Outstanding and expected to vest at December 31, 2021	383			0.92	$	35,537