Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2021

Share-based Payment Arrangement [Abstract]

Summary of Activity under Stock Option Plans

The following table summarizes activity under the Company’s stock option plans:

	Number of Shares Underlying Outstanding Options	Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value (in thousands)
Balances at December 31, 2020	4,858,590	$	3.83	5.80	$	149,046
Granted	1,500,000	38.80
Exercised	(2,035,709)	3.53
Forfeited and canceled	(58,813)	4.42
Balances at December 31, 2021	4,264,068	16.29		6.37	76,025
Vested and exercisable as of December 31, 2021	2,542,329	4.02		4.80	76,626
Vested and expected to vest as of December 31, 2021	4,264,068	16.29		6.37	76,025

The 90-day volume weighted-average common stock price targets, and the number of shares of the CEO Award that become vested with respect to the Market Condition upon the achievement of each such target, are reflected in the following table:

Stock Price	Number of Shares Vested
$60	100,000
$70	200,000
$80	300,000
$90	400,000
$100	500,000

Summary of Fair Value Assumptions on Stock Options Granted

The expected volatility is derived from the average historical stock volatility of the Company over a period equivalent to the expected term of the CEO Award. The following assumptions were used to estimate the fair value of the CEO Award:

Dividend yield	—	%
Risk-free interest rates	1.7	%
Expected volatility	65	%

Summary of Fair Value Assumptions on Employee Stock Purchas Plans

The fair values of the awards modified by the Transition Agreement were estimated using the Black-Scholes valuation model with the following assumptions:

Dividend yield	—	%
Expected term (in years)	0.3 - 1.3
Risk-free interest rates	1.5% - 1.6%
Expected volatility	38% - 39%

For the years ended December 31, 2021, 2020, and 2019, the assumptions used to determine the fair value of the shares to be awarded was estimated on the grant date using the Black-Scholes valuation model with the following assumptions:

	2021		2020		2019
Dividend yield	—	%	—	%	—	%
Expected term (in years)	0.5 - 2.0		0.5 - 2.0		0.5 - 2.0
Risk-free interest rates	—% - 0.5%		0.1% - 0.2%		1.5% - 2.4%
Expected volatility	60% - 76%		50% - 82%		38%

Summary of Activity under RSU Plans

The following table summarizes the RSU and PSU activity and related information under the 2018 EIP:

	Number Outstanding	Weighted-Average Grant Date Fair Value
Unvested balance - January 1, 2021	5,568,225	$	12.20
Granted	2,075,311	51.53
Vested	(1,865,444)	16.37
Forfeited/canceled	(1,194,269)	16.42
Unvested balance - December 31, 2021	4,583,823	$	26.86

Summary of Components of Stock-Based Compensation Expense Recognized

The following table summarizes the components of stock-based compensation expense recognized in the consolidated statements of operations for the years ended December 31, 2021, 2020, and 2019:

(In thousands)	2021		2020		2019
Cost of revenue	$	794	$	779	$	456
Research and development	16,232		9,783		6,471
Sales and marketing	5,923		4,440		2,609
General and administrative	30,643		10,506		9,262
Total	$	53,592	$	25,508	$	18,798