Stock-based Compensation (Tables)

9 Months Ended

Sep. 30, 2019

Share-based Payment Arrangement [Abstract]

Schedule of Stock-based Awards

The following table summarizes the stock options activity under the 2010 Plan:

	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, 2018	25,087	$	2.18	8.4	$	159,945
Options granted	394	$	9.60
Options exercised	(2,589)	$	2.24		$	21,188
Repurchase of unvested shares	—
Options canceled/forfeited/expired	(1,014)	$	2.46
Balances as of September 30, 2019	21,878	$	2.30	7.8	$	355,967
Vested and expected to vest as of September 30, 2019	21,878	$	2.30	7.8	$	355,967
Exercisable as of September 30, 2019	21,865	$	2.30	7.8	$	355,755

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,
	2019		2018
Expected term (in years)	6.2		6.5
Expected volatility	40.3	%	43.5	%
Risk-free interest rate	2.3	%	2.9	%
Dividend yield	—		—

Schedule of Restricted Stock Units Activity

RSU activity for the nine months ended September 30, 2019 was as follows:

	RSUs	Weighted-Average Grant Date Fair Value
	(in thousands, except per share data)
Unvested and outstanding as of December 31, 2018	—
Granted	6,465	$	9.74
Vested	(317)	$	8.62
Forfeited	(280)	$	8.70
Unvested as of September 30, 2019	5,868	$	9.85
Vested and not yet released	317	$	8.62
Outstanding as of September 30, 2019	6,185	$	9.79

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,
	2019		2018
Expected term (in years)	0.7		N/A
Risk-free interest rate	1.8	%	N/A
Expected volatility	35.6	%	N/A
Dividend yield	—		N/A

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,
	2019		2018		2019		2018
	(in thousands)
Cost of revenue	$	397	$	37	$	463	$	87
Sales and marketing	4,880		290		5,434		678
Research and development	7,801		461		8,624		1,078
General and administrative	9,833		23,648		10,491		24,442
Total stock-based compensation expense	$	22,911	$	24,436	$	25,012	$	26,285