Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2022

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

Summary of stock option activity

	Outstanding Options and RSUs
					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, 2021	4,319	5,900	$	17.54	5.40	$	451,505
Additional shares authorized	3,500	—
Options granted	(265)	265	$	61.39
Options exercised	—	(785)	$	7.60
Options forfeited/cancelled	35	(35)	$	38.91
RSUs granted	(4,877)	—
RSUs forfeited/cancelled	532	—
Balance at September 30, 2022	3,244	5,345	$	21.04	5.10	$	149,931
Exercisable at September 30, 2022		4,555	$	12.12	4.53	$	145,939
Vested and expected to vest at September 30, 2022		5,294	$	20.56	5.07	$	149,685

Schedule of performance-based awards

Period Granted	Options Granted	RSUs Granted	Options Vested	RSUs Vested	Milestone	Valuation Method
(in thousands)
Q1 2019	200	300	200	300	(1)	Monte-Carlo Simulation
Q2 2019	—	188	—	140	(2)	Grant Date Stock Price
Q3 2019	—	50	—	50	(1)	Monte-Carlo Simulation
Q1 2020	150	300	150	300	(1)	Monte-Carlo Simulation
Q1 2020	—	436	—	408	(3)	Grant Date Stock Price
Q1 2020	129	—	129	—	(3)	Black-Scholes-Merton
Q2 2020	—	21	—	21	(3)	Grant Date Stock Price
Q3 2020	10	—	10	—	(4)	Black-Scholes-Merton
Q3 2020	—	27	—	17	(3)	Grant Date Stock Price
Q4 2020	—	32	—	19	(1)	Monte-Carlo Simulation
Q4 2020	—	22	—	2	(5)	Grant Date Stock Price
Q1 2021	150	125	—	—	(1)	Monte-Carlo Simulation
Q1 2021	—	279	—	15	(3)	Grant Date Stock Price
Q2 2021	163	—	—	—	(1)	Monte-Carlo Simulation
Q2 2021	29	—	—	—	(3)	Black-Scholes-Merton
Q2 2021	—	7	—	2	(3)	Grant Date Stock Price
Q4 2021	—	20	—	—	(1)	Monte-Carlo Simulation
Q4 2021	—	205	—	37	(3)	Grant Date Stock Price
Q1 2022	110	—	—	—	(3)	Black-Scholes-Merton
Q1 2022	—	849	—	—	(3)	Grant Date Stock Price
Q2 2022	—	103	—	—	(3)	Grant Date Stock Price
Q3 2022	—	54	—	4	(2)	Grant Date Stock Price

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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 vest based on achievement of certain revenue targets, units, and system implementation, contingent upon the completion of requisite service through the date of such vesting.

(4) The awards have vested based on a change of coverage.

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

Restricted stock units

		Weighted-
		Average
		Grant Date
(in thousands, except for grant date fair value)	Shares	Fair Value
Balance at December 31, 2021	3,988	$	74.33
Granted	4,877	$	43.89
Vested	(1,090)	$	57.54
Cancelled/forfeited	(532)	$	56.92
Balance at September 30, 2022	7,243	$	57.86

Summary of stock-based compensation expenses

The following tables present the effect of employee and non-employee stock-based compensation expense on selected statements of operations line items for the three and nine months ended September 30, 2022 and 2021.

	Three months ended September 30,
	2022						2021
	Employee		Non-Employee		Total		Employee		Non-Employee		Total
	(in thousands)
Cost of revenues	$	2,124	$	—	$	2,124	$	1,262	$	—	$	1,262
Research and development		12,972		497		13,469		6,242		410		6,652
Selling, general and administrative		24,524		221		24,745		18,478		67		18,545
Total	$	39,620	$	718	$	40,338	$	25,982	$	477	$	26,459

	Nine months ended September 30,
	2022						2021
	Employee		Non-Employee		Total		Employee		Non-Employee		Total
	(in thousands)
Cost of revenues	$	5,903	$	—	$	5,903	$	3,246	$	—	$	3,246
Research and development		33,911		1,432		35,343		16,168		974		17,142
Selling, general and administrative		74,700		452		75,152		64,231		178		64,409
Total	$	114,514	$	1,884	$	116,398	$	83,645	$	1,152	$	84,797

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,
	2022			2021			2022					2021
Expected term (years)		6.05			10.00		5.12		—	10.00		5.11		—	10.00
Expected volatility		61.63	%		56.31	%	55.91	%	—	62.30	%	55.33	%	—	63.30	%
Expected dividend rate		0.00	%		0.00	%				0.00	%				0.00	%
Risk-free interest rate		3.15	%		1.30	%	1.62	%	—	3.15	%	0.81	%	—	1.67	%