Employee Benefit Plans (Tables)

6 Months Ended

Jun. 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		2,636,878		$	21.77
Exercised		(1,229,180	)	$	14.45
Forfeited		(774,324	)	$	19.35
Expired		(81,383	)	$	19.49
Outstanding, vested and expected to vest at June 30, 2021		15,652,133		$	16.98	$	67,395		6.8
Vested and exercisable at June 30, 2021		10,668,302		$	15.68	$	58,283		5.9

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 June 30,		Six Months Ended June 30,
	2021	2020	2021	2020
Expected life (in years)	6.2	6.2	5.8	5.8
Risk-free interest rate	1.2%	0.5%	0.8%	1.4%
Volatility	51%	52%	51%	48%
Dividend yield	—%	—%	—%	—%
Fair value of common stock	$18.39	$19.24	$21.70	$21.15

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 June 30,		Six Months Ended June 30,
	2021	2020	2021	2020
Expected life (in years)	1.3	1.3	1.3	1.3
Risk-free interest rate	0.1%	0.2%	0.1%	0.2%
Volatility	53%	58%	53%	58%
Dividend yield	—%	—%	—%	—%
Fair value of common stock	$19.12	$19.81	$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 June 30,				Six Months Ended June 30,
(in thousands)	2021		2020		2021		2020
Cost of revenue	$	1,580	$	1,047	$	3,062	$	2,007
Research and development		10,313		7,496		19,810		13,953
Sales and marketing		6,414		4,841		12,192		9,184
General and administrative		7,266		6,087		14,108		11,829
Stock-based compensation expense, net of amounts capitalized		25,573		19,471		49,172		36,973
Capitalized stock-based compensation expense		577		710		1,136		1,486
Stock-based compensation expense	$	26,150	$	20,181	$	50,308	$	38,459

Summary of Unamortized Stock-based Compensation

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

	Unrecognized stock-based compensation (in thousands)		Weighted average vesting period (in years)
Restricted stock units	$	140,150		2.4
Stock options		41,763		2.3
Restricted stock awards		5,872		2.3
ESPP		7,127		1.9
Total unrecognized stock-based compensation	$	194,912

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		3,279,068		$	25.56
Vested		(1,993,215	)	$	17.83
Forfeited/cancelled		(981,563	)	$	19.84
Unvested at June 30, 2021		7,305,145		$	20.93		1.2

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		274,417		$	26.89
Vested		(51,619	)	$	21.21
Forfeited/cancelled		(64,823	)	$	26.89
Unvested at June 30, 2021		260,435		$	24.64		2.1