Employee Benefit Plans (Tables)

9 Months Ended

Sep. 30, 2021

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

Summary of Stock Option Activity

The following is a summary of stock option activity for the current year period:

	Stock Options
	Number of Shares			Weighted Average Exercise Price		Aggregate Intrinsic Value (in thousands)		Weighted Average Remaining Contractual Term (in years)
Outstanding at December 31, 2020		15,100,142		$	16.07	$	143,156		6.9
Granted		2,904,930		$	21.61
Exercised		(1,543,809	)	$	13.95
Forfeited		(1,133,816	)	$	19.59
Expired		(106,057	)	$	19.35
Outstanding, vested and expected to vest at September 30, 2021		15,221,390		$	17.06	$	47,918		6.5
Vested and exercisable at September 30, 2021		10,986,983		$	15.92	$	43,565		5.6

Summary of Estimated Fair Value of Stock Options Granted Using Weighted-average Assumptions

Except for the Executive Option Grant discussed above, the Company used the Black-Scholes-Merton option pricing model to estimate the fair value of stock options granted using the following weighted-average assumptions:

	Three Months Ended September 30,			Nine Months Ended September 30,
	2021	2020	2021		2020
Expected life (in years)	5.7	5.6	5.8		5.8
Risk-free interest rate	0.9%	0.4%	0.8%		1.2%
Volatility	50%	52%	52%		48%
Dividend yield	—%	—%	—%		—%
Fair value of common stock	$20.05	$24.10	$21.51		$21.47

Summary of Estimated Fair Value of ESPP Purchase Rights Granted Using Weighted-average Assumptions

The Company used the Black-Scholes-Merton option pricing model to estimate the fair value of ESPP purchase rights granted using the following weighted-average assumptions:

	Three Months Ended September 30,			Nine Months Ended September 30,
	2021	2020	2021		2020
Expected life (in years)	n/a	n/a	1.3		1.3
Risk-free interest rate	n/a	n/a	0.1%		0.2%
Volatility	n/a	n/a	53%		58%
Dividend yield	n/a	n/a	—%		—%
Fair value of common stock	n/a	n/a	$19.12		$19.81

Summary of Stock-based Compensation Expense Recognized in Financial Statements

Stock-based compensation expense recognized in the condensed consolidated financial statements is as follows:

	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2021		2020		2021		2020
Cost of revenue	$	1,639	$	1,222	$	4,701	$	3,229
Research and development		10,081		8,322		29,891		22,275
Sales and marketing		5,672		5,912		17,864		15,096
General and administrative		7,202		6,150		21,310		17,979
Stock-based compensation expense, net of amounts capitalized		24,594		21,606		73,766		58,579
Capitalized stock-based compensation expense		530		206		1,666		1,692
Stock-based compensation expense	$	25,124	$	21,812	$	75,432	$	60,271

Summary of Unamortized Stock-based Compensation

As of September 30, 2021, unamortized stock-based compensation was as follows:

	Unrecognized stock-based compensation (in thousands)		Weighted average vesting period (in years)
Restricted stock units	$	129,340		2.3
Stock options		34,430		2.2
Restricted stock awards		6,130		2.3
ESPP		5,564		1.6
Total unrecognized stock-based compensation	$	175,464

Restricted Stock Units

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

Summary of Restricted Stock Units and Restricted Stock Awards

The following is a summary of restricted stock units for the current year period:

	Restricted Stock Units
	Number of Shares			Weighted Average Grant-Date Fair Value		Weighted Average Remaining Contractual Term (in years)
Unvested at December 31, 2020		7,000,855		$	17.72		1.1
Granted		4,262,348		$	24.32
Vested		(2,924,389	)	$	18.24
Forfeited/cancelled		(1,618,582	)	$	20.45
Unvested at September 30, 2021		6,720,232		$	21.03		1.1

Restricted Stock Awards

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

Summary of Restricted Stock Units and Restricted Stock Awards

The following is a summary of restricted stock awards for the current year period:

	Restricted Stock Awards
	Number of Shares			Weighted Average Grant-Date Fair Value		Weighted Average Remaining Contractual Term (in years)
Unvested at December 31, 2020		102,460		$	18.30		1.2
Granted		329,417		$	25.68
Vested		(86,163	)	$	21.78
Forfeited/cancelled		(64,823	)	$	26.89
Unvested at September 30, 2021		280,891		$	23.91		2.1