Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2020

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

Schedule of performance-based awards

Period Granted	Options Granted	RSUs Granted	Options Vested	RSUs Vested	Milestone	Valuation Method
(in thousands)
Q1 2019	200	300	118	184	(1)	Monte-Carlo Simulation
Q2 2019	—	188	—	—	(2)	Fair Market Value
Q3 2019	—	50	—	25	(1)	Monte-Carlo Simulation
Q1 2020	150	300	38	131	(1)	Monte-Carlo Simulation
Q1 2020	—	436	—	4	(3)	Fair Market Value
Q1 2020	129	—	—	—	(3)	Black-Scholes-Merton
Q2 2020	—	21	—	—	(3)	Fair Market Value
Q3 2020	10	—	7	—	(4)	Black-Scholes-Merton
Q3 2020	—	27	—	3	(3)	Fair Market Value

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(1) The awards will vest based on the achievement of certain values of the Company’s common stock at multiple thresholds within certain periods and are contingent upon the completion of requisite service through the date of such vesting.

(2) The vesting of the awards will be triggered after the end of the achievement milestone, as measured by the Company.

(3) The awards will vest based on achievement of certain revenue target and are contingent upon the completion of requisite service through the date of such vesting.

(4) The awards will vest based on a change of coverage.

Summary of stock option activity

The following table summarizes option activity for the nine months ended September 30, 2020:

	Outstanding Options
					Weighted-
			Weighted-		Average
	Shares		Average		Remaining	Aggregate
	Available for	Number of	Exercise		Contractual	Intrinsic
(in thousands, except for contractual life and exercise price)	Grant	Shares	Price		Life	Value
					(in years)
Balance at December 31, 2019	6,416	8,497	$	10.39	6.88	$	197,955
Additional shares authorized	3,120	—
Options granted	(457)	457	$	27.61
Options exercised	—	(1,534)	$	10.28
Options forfeited/cancelled	155	(155)	$	15.40
RSUs granted (1)	(5,143)	—
RSUs forfeited/cancelled	427	—
Balance at September 30, 2020	4,518	7,265	$	11.39	6.36	$	442,004
Exercisable at September 30, 2020		5,382	$	9.34	5.71	$	338,529
Vested and expected to vest at September 30, 2020		7,148	$	11.30	6.33	$	435,595

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(1) – The RSUs and options are granted under the 2015 Stock Plan. RSUs granted impact the shares available for grant pool at a 2 to 1 ratio.

Restricted stock units

		Weighted-
		Average
		Grant Date
(in thousands, except for grant date fair value)	Shares	Fair Value
Balance at December 31, 2019	2,404	$	19.86
Granted	2,571	$	29.83
Vested	(861)	$	17.48
Cancelled/forfeited	(213)	$	24.11
Balance at September 30, 2020	3,901	$	25.80

Summary of stock-based compensation expenses

	Three months ended September 30,
	2020						2019
	Employee		Non-Employee		Total		Employee		Non-Employee		Total
	(in thousands)
Cost of revenues	$	458	$	—	$	458	$	258	$	11	$	269
Research and development		3,081		17		3,098		1,580		—		1,580
Selling, general and administrative		11,404		72		11,476		8,312		86		8,398
Total	$	14,943	$	89	$	15,032	$	10,150	$	97	$	10,247

	Nine months ended September 30,
	2020						2019
	Employee		Non-Employee		Total		Employee		Non-Employee		Total
	(in thousands)
Cost of revenues	$	1,213	$	—	$	1,213	$	641	$	21	$	662
Research and development		7,394		459		7,853		3,738		—		3,738
Selling, general and administrative		25,183		157		25,340		15,184		518		15,702
Total	$	33,790	$	616	$	34,406	$	19,563	$	539	$	20,102

Performance-based awards

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

Schedule of assumptions used in valuation of fair value

	September 30,
	2020
Risk-free interest rate		0.61	%	—	1.64	%
Expected dividend yield					0.00	%
Expected volatility		55	%	—	65	%
Expected term (years)		5.25		—	7.25

Employee stock options

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

Schedule of assumptions used in valuation of fair value

	Three months ended September 30,										Nine months ended September 30,
	2020					2019					2020					2019
Expected term (years)	5.22		—	10.0		5.23		—	10.00		5.22		—	10.00		5.23		—	10.00
Expected volatility	54.18	%		61.96	%	43.07	%	—	45.84	%	49.94	%	—	61.96	%	42.53	%	—	45.84	%
Expected dividend rate				0.00	%				0.00	%				0.00	%				0.00	%
Risk-free interest rate	0.31	%	—	0.65	%	1.60	%	—	2.12	%	0.31	%	—	1.70	%	1.60	%	—	2.60	%