STOCK-BASED COMPENSATION (Tables)

12 Months Ended

Dec. 31, 2019

Share-based Payment Arrangement [Abstract]

Summary of the Components of Total Stock-Based Compensation Expense

The following table summarizes the components of total stock-based compensation expense included in the consolidated statements of operations for the periods presented.

	Years Ended December 31,
	2019		2018		2017
	(In thousands)
Cost of revenues	$	1,650	$	1,071	$	1,072
Research and development	4,897		2,940		2,573
Sales and marketing	5,678		3,074		1,157
General and administrative	7,216		4,347		1,925
Restructuring	735		—		—
Total	$	20,176	$	11,432	$	6,727

Summary of Stock-Based Compensation Associated with Each Type of Award

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

	Years Ended December 31,
	2019		2018		2017
	(In thousands)
Stock options, RSUs, and PSUs	$	19,216	$	10,691	$	5,559
Employee stock purchase plan	960		741		1,168
Total	$	20,176	$	11,432	$	6,727

Summary of the Weighted-Average Grant Date Fair Value of Options Granted

The following table presents the weighted-average grant date fair value of options granted for the periods presented and the assumptions used to estimate those values using a Black-Scholes option pricing model.

	Years Ended December 31,
	2019			2018			2017
Weighted average grant date fair value	$	9.16		$	2.83		$	0.76
Expected term (in years)	3.8			4.0			4.4
Expected volatility	89.1		%	88.5		%	83.9		%
Annual risk-free rate of return	2.1		%	2.6		%	1.8		%
Dividend yield	—		%	—		%	—		%

Summary of Stock Option Activity

The following is a summary of stock option activity.

	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, 2016	8,730		$	4.55
Granted	4,500		1.22
Exercised	(425	)	0.51			$	544
Canceled	(4,379	)	6.91
Outstanding at December 31, 2017	8,426		$	1.77
Granted	213		4.43
Exercised	(1,346	)	1.75			5,096
Canceled	(521	)	2.94
Outstanding at December 31, 2018	6,772		$	1.76
Granted	43		14.58
Exercised	(2,616	)	1.22			31,093
Canceled	(102	)	4.07
Outstanding at December 31, 2019	4,097		$	2.18	4.3	$	98,103
Vested and expected to vest at December 31, 2019	4,097		$	2.18	4.3	$	98,103
Exercisable at December 31, 2019	2,887		$	2.44	4.1	$	68,397

(1)

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 December 31, 2019 is based on the closing price of the Company’s stock fair value on December 31, 2019 or the earlier of the last trading day prior to December 31, 2019, if December 31, 2019 is a non-trading day. The Company’s stock fair value used in this computation was $26.13 per share.

Summary of Stock Option Outstanding

The following table summarizes information about stock options outstanding at December 31, 2019.

	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)
$0.64 —– $1.11	774	5.0	$	0.82	518	$	0.78
$1.29 —– $1.29	1,000	4.7	1.29		563	1.29
$1.31 —– $1.31	1,309	4.3	1.31		975	1.31
$1.37 —– $7.50	867	3.2	4.18		702	4.57
$7.68 —– $14.58	147	3.4	11.45		129	11.02
Total	4,097	4.3	$	2.18	2,887	$	2.44

Summary of Restricted Stock Unit Activity

The following is a summary of RSU activity.

	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, 2016	606		$	9.33
Granted	5,418		1.46
Vested	(885	)	3.81			$	932
Canceled	(1,634	)	1.90
Outstanding at December 31, 2017	3,505		$	2.03
Granted	3,152		4.45
Vested	(1,399	)	2.75			6,657
Canceled	(906	)	2.17
Outstanding at December 31, 2018	4,352		$	3.52
Granted	2,112		11.50
Vested	(1,707	)	3.87			27,156
Canceled	(494	)	4.81
Outstanding at December 31, 2019	4,263		$	7.19	1.3	$	111,387
Expected to vest at December 31, 2019	4,263		$	7.19	1.3	$	111,387

(1)

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 December 31, 2019 is based on the closing price of the Company’s stock on December 31, 2019 or the earlier of the last trading day prior to December 31, 2019, if December 31, 2019 is a non-trading day. The Company’s stock fair value used in this computation was $26.13 per share.

Share-based Compensation, Performance Shares Award Outstanding Activity

The following is a summary of PSU activity.

	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, 2017	—
Granted	1,477		$	4.65
Vested	—
Canceled	(147	)
Outstanding at December 31, 2018	1,330		$	4.66
Granted	1,052		9.48
Vested	(1,063	)	4.62			$	10,818
Canceled	(364	)	5.16
Outstanding at December 31, 2019	955		$	9.83	0.2	$	24,952

(1)

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 December 31, 2019 is based on the closing price of the Company’s stock on December 31, 2019 or the earlier of the last trading day prior to December 31, 2019, if December 31, 2019 is a non-trading day. The Company’s stock fair value used in this computation was $26.13 per share.

Schedule of Share-based Compensation, Employee Stock Purchase Plan, Activity

A summary of ESPP activity for the years presented is as follows: (in thousands, except per share data):

	Years Ended December 31,
	2019		2018		2017
Proceeds from common stock issued under ESPP	$	1,692	$	397	$	313
Shares of common stock issued	315		439		478
Weighted-average price per share	$	5.37	$	0.90	$	0.65