Equity Incentive Plans (Tables)

12 Months Ended

Dec. 31, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Changes in Shares Available for Grant

Changes in shares available for grant during the year ended December 31, 2019 were as follows:

	Shares Available for Grant
Shares available for grant at December 31, 2018		6,827,996
2009 Plan reserve cancelled		(3,155,968	)
2019 Plan reserve established		15,519,170
Options and restricted stock units granted		(4,207,301	)
Options and restricted stock units forfeited or cancelled		412,357
Shares available for grant at December 31, 2019		15,396,254

Summary of Stock Option Activity Under 2008 Plan 2009 Plan and 2019 Plan

Stock option activity under the 2008 Plan, 2009 Plan and 2019 Plan during the year ended December 31, 2019, 2018 and 2017 was as follows:

	Shares Subject to Outstanding Options			Weighted- Average Exercise Price per Share		Aggregate Intrinsic Value (in thousands)
Options outstanding at December 31, 2016		12,919,342		$	3.28	$	41,952
Options granted		1,604,496			6.27
Options forfeited or cancelled		(2,207,933	)		5.51
Options exercised		(226,211	)		0.98
Options outstanding at December 31, 2017		12,089,694			3.56		36,165
Options granted		4,764,625			6.55
Options forfeited or cancelled		(929,519	)		4.86
Options exercised		(766,870	)		1.66
Options outstanding at December 31, 2018		15,157,930			4.52		41,690
Options granted		4,194,491			9.72
Options forfeited or cancelled		(412,357	)		6.24
Options exercised		(2,293,410	)		1.97
Options outstanding at December 31, 2019		16,646,654		$	6.14	$	398,379
Options vested and exercisable at December 31, 2019		10,101,496		$	4.58	$	255,939

Summary of Estimated Fair Value of Options Granted

The estimated fair value of options granted during the year ended December 31, 2019, 2018 and 2017 was estimated using the Black-Scholes option-pricing model with the following assumptions:

	Year Ended December 31,
	2019		2018		2017
Grant date fair value	$7.80 - $47.81		$6.55		$6.27 - $6.32
Expected term (in years)	5.27 - 6.08		6.08 - 10.00		6.08 - 10.00
Risk-free interest rate	1.4% - 2.5%		2.6% - 3.0%		1.9% - 2.4%
Expected volatility	64.3% - 72.9%		65.0% - 69.2%		67.3% - 70.5%
Expected dividend yield		—		—		—

Summary of Compensation Costs Related to Stock Options and RSUs Included on Statements of Operations

The compensation costs related to stock options and RSUs for the year ended December 31, 2019, 2018 and 2017, respectively, are included on our statements of operations as follows (in thousands):

	Year Ended December 31,
	2019		2018		2017
Cost of revenue	$	555	$	398	$	237
Research and development		3,934		2,896		2,375
Sales and marketing		3,480		2,891		1,344
General and administration		5,155		4,964		3,053
Total share-based compensation expense	$	13,124	$	11,149	$	7,009