Stock-Based Compensation Expense (Tables)

9 Months Ended

Sep. 30, 2020

Share-based Payment Arrangement [Abstract]

Schedule of Stock-Based Compensation Expense

Stock-based compensation expense for restricted stock units, stock options and issuances of common stock pursuant to our employee stock purchase plan was classified in the accompanying consolidated statements of operations as follows:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
	(in thousands)
Stock-based compensation expense:
Cost of revenue	$	1,132	$	679	$	3,194	$	1,970
Research and development	6,818		3,996		17,852		11,224
Sales and marketing	4,506		3,047		12,529		8,453
General and administrative	4,672		2,704		13,346		7,843
Total stock-based compensation expense	$	17,128	$	10,426	$	46,921	$	29,490

Summary of Restricted Stock and Restricted Stock Unit Activity

Restricted stock unit activity during the nine months ended September 30, 2020 was as follows:

	Shares	Weighted-Average Grant Date Fair Value
Unvested balance as of December 31, 2019	2,936,924	$	32.43
Granted	1,618,363	56.56
Vested	(1,092,477)	33.10
Forfeited	(201,187)	39.92
Unvested balance as of September 30, 2020	3,261,623	$	43.74

Summary of Stock Option Activity

Stock option activity during the nine months ended September 30, 2020 was as follows:

	Shares	Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding as of December 31, 2019	2,735,392	$	10.10
Granted	—	—
Exercised	(652,160)	9.55			$	31,337
Forfeited/cancelled	(16,484)	17.01
Outstanding as of September 30, 2020	2,066,748	$	10.21	4.4	$	105,458
Vested and exercisable as of September 30, 2020	1,906,500	$	9.75	4.2	$	98,167