Stockholders' Equity (Tables)

9 Months Ended

Sep. 30, 2020

Equity [Abstract]

Stock-Based Compensation Expense Related to Grants of Employee Stock Options, Restricted Stock Units (RSUs) and Performance and Market Based Awards

We recorded stock-based compensation expense related to grants of employee stock options, restricted stock units (“RSUs”) and performance and market-based awards in our consolidated statements of operations as follows (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
Cost of revenue	$	566	$	407	$	1,548	$	1,088
Research and development		25,380		12,029		48,595		35,982
Sales and marketing		3,957		3,046		10,960		8,453
General and administrative		8,821		5,857		23,759		15,944
Total stock-based compensation expense	$	38,724	$	21,339	$	84,862	$	61,467

Schedule of Share Based Compensation Stock Option Activity

The following table shows stock option activity for the nine months ended September 30, 2020 (in thousands, except weighted-average exercise price and weighted-average contractual term):

	Outstanding Options
						Aggregate		Weighted-
				Weighted-Average		Intrinsic Value of		Average
				Exercise Price		Stock Options		Contractual Term
	Stock Options			(per option)		Outstanding		(in years)
Balance as of December 31, 2019		31,204		$	3.24	$	89,786		7.19
Granted		1,633			6.55
Forfeited, expired and cancelled		(19	)		3.37
Exercised		(2,435	)		2.93
Balance as of September 30, 2020		30,383		$	3.45	$	172,404		6.68

Weighted-Average Grant Date Fair Value of Stock Options and Related Assumptions

The following table presents the weighted-average grant date fair value and the related assumptions used to estimate the fair value of our stock options:

	Nine Months Ended September 30,
	2020
Expected term, in years		6
Risk-free interest rates		0.8	%
Expected volatility		36.0	%
Dividend yield		—
Weighted-average estimated fair value of options granted	$	2.35

Schedule of Share Based Compensation Restricted Stock Units Award Activity

The following table shows a summary of RSU activity for the nine months ended September 30, 2020, which includes performance and market-based awards (in thousands, except weighted-average grant date fair value):

	Outstanding RSUs
				Weighted-Average		Aggregate
				Grant Date Fair Value		Intrinsic Value of
	Shares			(per share)		Unvested RSUs
Unvested as of December 31, 2019		40,188		$	4.23	$	245,951
Granted		43,085			8.60
Vested		(13,650	)		4.04
Forfeited		(1,946	)		4.53
Unvested as of September 30, 2020		67,677		$	7.04	$	619,921