Stock-based Compensation (Tables)

9 Months Ended

Sep. 30, 2020

Share-based Payment Arrangement [Abstract]

Schedule of Stock-based Awards

The following table summarizes the stock options activity under the 2010 Plan and 2019 Plan for the nine months ended September 30, 2020:

	Stock Options Outstanding
	(in thousands, except year and per share data)
	Shares Subject to Options Outstanding	Weighted- Average Exercise Price per Option		Weighted- Average Remaining Contractual Terms (in years)	Aggregate Intrinsic Value
Balances as of December 31, 2019	21,191	$	2.30	7.4	$	312,720
Options granted	1,710	$	18.05
Options exercised	(3,587)	$	1.58		$	90,829
Options canceled/forfeited/expired	(249)	$	2.62
Balances as of September 30, 2020	19,065	$	3.85	7.2	$	709,484
Vested and expected to vest as of September 30, 2020	19,065	$	3.85	7.2	$	709,484
Exercisable as of September 30, 2020	17,361	$	2.46	7.0	$	670,147

Schedule of Assumptions Used to Determine the Fair Value of Stock Options Granted

The weighted-average assumptions used to determine the fair value of stock options granted during the periods presented were as follows:

	Nine months ended September 30,
	2020		2019
Expected term (in years)	6.0		6.2
Expected volatility	40.3	%	40.3	%
Risk-free interest rate	0.7	%	2.3	%
Dividend yield	—		—

Schedule of Restricted Stock Units Activity

Restricted stock and RSU activity for the nine months ended September 30, 2020 was as follows:

	Restricted Stock and RSUs	Weighted-Average Grant Date Fair Value
	(in thousands, except per share data)
Unvested and outstanding as of December 31, 2019	6,508	$	11.08
Granted - RSUs	3,310	$	27.31
Granted - Restricted stock	949	$	17.06
Vested - RSUs	(1,723)	$	11.35
Vested - Restricted stock	(107)	$	17.06
Forfeited	(413)	$	12.55
Unvested as of September 30, 2020	8,524	$	16.18
Vested and not yet released	18	$	36.77
Outstanding as of September 30, 2020	8,542	$	16.22

Schedule of Fair Value Assumptions for Employee Stock Purchase Plan

The weighted-average assumptions used to determine the fair value of the ESPP during the periods presented were as follows:

	Nine months ended September 30,
	2020		2019
Expected term (in years)	0.5		0.7
Risk-free interest rate	0.15	%	1.81	%
Expected volatility	65.20	%	35.6	%
Dividend yield	—		—	%

Schedule of Stock-based Compensation Expense

The following table sets forth the total stock-based compensation expense included in the Company’s condensed consolidated statements of operations:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
	(in thousands)
Cost of revenue	$	311	$	397	$	858	$	463
Sales and marketing	4,406		4,880		11,177		5,434
Research and development	6,749		7,801		18,213		8,624
General and administrative	3,279		9,833		9,843		10,491
Total stock-based compensation expense	$	14,745	$	22,911	$	40,091	$	25,012