Stock-based compensation expense for all stock-based awards expected to vest is measured at fair value on the date of grant and recognized ratably over the requisite service period. The following table summarizes the components of total stock-based compensation expense included in the condensed consolidated statements of operations for the periods presented.



	Three Months Ended March 31,
	2020		2019
	(In thousands)
Cost of revenues	$	606	$	231
Research and development	1,919		716
Sales and marketing	1,942		999
General and administrative	3,048		1,288
Restructuring	—		55
Total	$	7,515	$	3,289

The following table summarizes the various types of stock-based compensation expense for the periods presented.



	Three Months Ended March 31,
	2020		2019
	(In thousands)
Stock options, RSUs, and PSUs	$	7,077	$	3,222
Employee stock purchase plan	438		67
Total	$	7,515	$	3,289

As of March 31, 2020, there was approximately $40.6 million of total unrecognized stock-based compensation expense related to unvested equity awards, which are expected to be recognized over a weighted-average period of 2.8 years.

The fair value of each option granted was estimated on the date of grant using the Black-Scholes option-pricing model. No options were granted during the three months ended March 31, 2020 and 2019.

The fair value of the Company’s restricted stock units (“RSU”) awards granted is based upon the closing price of the Company’s stock price on the date of grant.

The fair value of the Company’s non-market performance stock units (“PSU”) awards granted was based upon the closing price of the Company’s stock price on the date of grant. The fair value of awards of the Company’s PSU awards containing market conditions was determined using a Monte Carlo simulation model based upon the terms of the conditions, the expected volatility of the underlying security, and other relevant factors.



	Number of Shares Outstanding		Weighted- Average Exercise Price per Share		Weighted- Average Remaining Contractual Term	Aggregate Intrinsic Value ⁽¹⁾
	(In thousands)				(Years)	(In thousands)
Outstanding at December 31, 2019	4,097		$	2.18
Granted	—		—
Exercised	(541	)	2.58			$	28,263
Canceled	(73	)	7.44
Outstanding at March 31, 2020	3,483		$	2.01	4.2	$	105,469
Vested and expected to vest at March 31, 2020	3,483		$	2.01	4.2	$	105,469
Exercisable at March 31, 2020	2,518		$	2.22	4.1	$	75,706

The intrinsic value of options exercised is based upon the value of the Company’s stock at exercise. The intrinsic value of options outstanding, vested and expected to vest, and exercisable as of March 31, 2020 is based on the closing price of the Company’s stock fair value on March 31, 2020 or the earlier of the last trading day prior to March 31, 2020, if March 31, 2020 is a non-trading day. The Company’s stock fair value used in this computation was $32.29 per share.



	Options Outstanding				Options Exercisable
Range of Exercise Prices	Number of Shares	Weighted- Average Remaining Life	Weighted- Average Exercise Price		Number of Shares	Weighted- Average Exercise Price
	(In thousands)	(Years)			(In thousands)
$0.70 —– $1.11	751	4.8	$	0.82	565	$	0.80
$1.29 —– $1.29	1,000	4.5	1.29		625	1.29
$1.31 —– $1.31	1,037	4.0	1.31		765	1.31
$1.37 —– $12.57	653	3.3	4.78		527	5.34
$14.58 —– $14.58	42	6.1	14.58		36	14.58
Total	3,483	4.2	$	2.01	2,518	$	2.22



	Number of Shares Outstanding		Weighted- Average Fair Value per Share at Grant Date		Weighted- Average Remaining Contractual Term	Aggregate Intrinsic Value ⁽¹⁾
	(In thousands)				(Years)	(In thousands)
Outstanding at December 31, 2019	4,263		$	7.19
Granted	552		31.34
Vested	(951	)	6.13			$	34,095
Canceled	(34	)	16.92
Outstanding at March 31, 2020	3,830		$	10.85	1.3	$	123,672
Expected to vest at March 31, 2020	3,830		$	10.63	1.3	$	114,306

The intrinsic value of RSUs vested is based upon the value of the Company’s stock when vested. The intrinsic value of RSUs outstanding and expected to vest as of March 31, 2020 is based on the closing price of the Company’s stock on March 31, 2020 or the earlier of the last trading day prior to March 31, 2020, if March 31, 2020 is a non-trading day. The Company’s stock fair value used in this computation was $32.29 per share.



	Number of Shares Outstanding		Weighted- Average Fair Value per Share at Grant Date		Weighted- Average Remaining Contractual Term	Aggregate Intrinsic Value ⁽¹⁾
	(In thousands)				(Years)	(In thousands)
Outstanding at December 31, 2019	955		$	9.83
Granted	482		11.52
Vested	(1,410	)	10.41			$	50,938
Canceled	—		—
Outstanding at March 31, 2020	27		$	4.40	0	$	872

The intrinsic value of PSUs vested is based upon the value of the Company’s stock when vested. The intrinsic value of PSUs outstanding and expected to vest as of March 31, 2020 is based on the closing price of the Company’s stock on March 31, 2020 or the earlier of the last trading day prior to March 31, 2020, if March 31, 2020 is a non-trading day. The Company’s stock fair value used in this computation was $32.29 per share.