Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2021

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	169	260	(1)	Monte-Carlo Simulation
Q2 2019	—	188	—	81	(2)	Fair Market Value
Q3 2019	—	50	—	38	(1)	Monte-Carlo Simulation
Q1 2020	150	300	75	150	(1)	Monte-Carlo Simulation
Q1 2020	—	436	—	9	(3)	Fair Market Value
Q1 2020	129	—	—	—	(3)	Black-Scholes-Merton
Q2 2020	—	21	—	—	(3)	Fair Market Value
Q3 2020	10	—	10	—	(4)	Black-Scholes-Merton
Q3 2020	—	27	—	5	(3)	Fair Market Value
Q4 2020	—	32	—	6	(1)	Monte-Carlo Simulation
Q4 2020	—	22	—	2	(5)	Fair Market Value
Q1 2021	150	125	—	—	(1)	Monte-Carlo Simulation
Q1 2021	—	279	—	10	(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 a revenue target and are contingent upon the completion of requisite service through the date of such vesting.

(4) The awards vest based on achievement of a reimbursement target.

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(5) The awards will vest based on achievement of certain revenue and recruiting targets.

Summary of stock option activity

	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, 2020	3,197	6,707	$	11.19	6.04	$	592,468
Additional shares authorized	3,446	—
Options granted	(150)	150	$	119.73
Options exercised	—	(575)	$	7.95
Options forfeited/cancelled	17	(17)	$	12.64
RSUs granted	(1,180)	—
RSUs forfeited/cancelled	78	—
Balance at March 31, 2021	5,408	6,265	$	14.09	5.98	$	550,649
Exercisable at March 31, 2021		4,796	$	9.51	5.34	$	441,349
Vested and expected to vest at March 31, 2021		6,176	$	13.87	5.95	$	544,020

Restricted stock units

		Weighted-
		Average
		Grant Date
(in thousands, except for grant date fair value)	Shares	Fair Value
Balance at December 31, 2020	4,188	$	34.02
Granted	1,180	$	103.94
Vested	(632)	$	26.17
Cancelled/forfeited	(78)	$	35.35
Balance at March 31, 2021	4,658	$	52.38

Performance-based awards

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

Schedule of assumptions used in valuation of fair value

	March 31,
	2021
Risk-free interest rate		0.80	—	0.95	%
Expected dividend yield				0.00	%
Expected volatility				60	%
Expected term (years)		7.25	—	10.00

Employee and non-employee stock options

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

Summary of stock-based compensation expenses

	Three months ended March 31,
	2021						2020
	Employee		Non-Employee		Total		Employee		Non-Employee		Total
	(in thousands)
Cost of revenues	$	708	$	—	$	708	$	314	$	—	$	314
Research and development		3,650		224		3,874		1,682		160		1,842
Selling, general and administrative		18,604		46		18,650		5,252		9		5,261
Total	$	22,962	$	270	$	23,232	$	7,248	$	169	$	7,417

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 March 31,
	2021			2020
Expected term (years)		10.00		5.27		—	10.00
Expected volatility		55.33	%	49.94	%	—	58.53	%
Expected dividend rate		0	%				0	%
Risk-free interest rate		1.13	%	0.44	%	—	1.70	%