STOCK-BASED COMPENSATION (Tables)

The following table summarizes the stock-based compensation expense recognized in accordance with ASC 718-10 for the three and six months ended June 30, 2020, and June 30, 2019:


	Three Months Ended						Six Months Ended
(In thousands)	June 30, 2020		June 30, 2019		June 30, 2020		June 30, 2019
Cost of revenues	$	252	$	273	$	648	$	544
Research and development	2,351		2,144		4,460		3,776
Sales and marketing	1,258		1,141		2,650		2,202
General and administrative	2,120		1,938		4,933		3,381
Total stock-based compensation expense	$	5,981	$	5,496	$	12,691	$	9,903

A summary of stock options outstanding as of June 30, 2020, and activity during the six 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, 2020	167	$	38.88
Granted	—	—
Exercised	(90)	$	37.22
Forfeited or expired	—	—
Outstanding at June 30, 2020	77	$	40.81	1.51	$	5,973
Vested and exercisable at June 30, 2020	77			1.51	$	5,973

A summary of PSUs outstanding as of June 30, 2020, and activity during the six 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, 2020	61	$	70.11
Granted	73	$	92.12
Vested	(61)	$	70.11
Forfeited	—	—
Outstanding at June 30, 2020	73	$	92.12	0.50	$	8,652
Outstanding and expected to vest at June 30, 2020	50			0.50	$	5,961

A summary of PRSUs outstanding as of June 30, 2020, and activity during the six 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, 2020	144	$	64.05
Granted	73	$	98.75
Vested	—	—
Forfeited	—	—
Outstanding at June 30, 2020	217	$	75.70	1.50	$	25,540
Outstanding and expected to vest at June 30, 2020	100			2.23	$	11,808

A summary of RSUs outstanding as of June 30, 2020, and activity during the six 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, 2020	860	$	62.66
Granted	191	$	85.96
Vested	(288)	$	60.09
Forfeited	(11)	$	66.16
Outstanding at June 30, 2020	752	$	69.51	1.89	$	88,770
Outstanding and expected to vest at June 30, 2020	690			1.82	$	81,463