Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 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	201	300	(1)	Monte-Carlo Simulation
Q2 2019	—	188	—	81	(2)	Fair Market Value
Q3 2019	—	50	—	50	(1)	Monte-Carlo Simulation
Q1 2020	150	300	113	225	(1)	Monte-Carlo Simulation
Q1 2020	—	436	—	406	(3)	Fair Market Value
Q1 2020	129	—	129	—	(3)	Black-Scholes-Merton
Q2 2020	—	21	—	21	(3)	Fair Market Value
Q3 2020	10	—	10	—	(4)	Black-Scholes-Merton
Q3 2020	—	27	—	17	(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
Q2 2021	163	—	—	—	(1)	Monte-Carlo Simulation
Q2 2021	29	—	—	—	(3)	Black-Scholes-Merton
Q2 2021	—	7	—	—	(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	(391)	391	$	104.02
Options exercised	—	(1,051)	$	10.26
Options forfeited/cancelled	35	(35)	$	13.78
RSUs granted	(1,528)	—
RSUs forfeited/cancelled	227	—
Balance at September 30, 2021	4,986	6,012	$	17.37	5.63	$	566,871
Exercisable at September 30, 2021		4,785	$	9.99	4.98	$	485,498
Vested and expected to vest at September 30, 2021		5,936	$	17.00	5.60	$	561,788

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	1,528	$	104.48
Vested	(1,707)	$	25.83
Cancelled/forfeited	(227)	$	49.39
Balance at September 30, 2021	3,782	$	64.78

Summary of stock-based compensation expenses

	Three months ended September 30,
	2021						2020
	Employee		Non-Employee		Total		Employee		Non-Employee		Total
	(in thousands)
Cost of revenues	$	1,262	$	—	$	1,262	$	458	$	—	$	458
Research and development		6,242		410		6,652		3,081		17		3,098
Selling, general and administrative		18,478		67		18,544		11,404		72		11,476
Total	$	25,982	$	477	$	26,459	$	14,943	$	89	$	15,032

	Nine months ended September 30,
	2021						2020
	Employee		Non-Employee		Total		Employee		Non-Employee		Total
	(in thousands)
Cost of revenues	$	3,246	$	—	$	3,246	$	1,213	$	—	$	1,213
Research and development		16,168		974		17,142		7,394		459		7,853
Selling, general and administrative		64,231		178		64,409		25,183		157		25,340
Total	$	83,645	$	1,152	$	84,797	$	33,790	$	616	$	34,406

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,
	2021
Risk-free interest rate		0.80	%	—	1.42	%
Expected dividend yield					0.00	%
Expected volatility					60	%
Expected term (years)		7.25		—	10.00

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,
	2021			2020					2021					2020
Expected term (years)		10.00		5.22		—	10.00		5.11		—	10.00		5.22		—	10.00
Expected volatility		56.31	%	54.18	%	—	61.96	%	55.33	%	—	63.30	%	49.94	%	—	61.96	%
Expected dividend rate		0.00	%				0.00	%				0.00	%				0.00	%
Risk-free interest rate		1.30	%	0.31	%	—	0.65	%	0.81	%	—	1.67	%	0.31	%	—	1.70	%