Stock Plans and Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Schedule of Assumptions Used in Determining Fair Value of Shares Issuable

The fair value of shares issuable under the 2016 ESPP is determined using the Black-Scholes option pricing model with the following weighted average assumptions: 

	Three Months Ended September 30,				Nine Months Ended September 30,
	2021		2020		2021		2020
Employee Stock Purchase Plan:
Expected term (in years) (1)		0.50		0.50		0.50		0.50
Expected volatility (2)	45% - 60%		55% - 65%		45% - 60%		55% - 65%
Risk-free interest rate (3)	0.05% - 0.06%		0.12% - 0.29%		0.05% - 0.06%		0.12% - 0.29%
Dividend rate (4)	0%		0%		0%		0%

⁽¹⁾ The expected term represents the contractual term of the 2016 ESPP;

⁽²⁾ The expected volatility of the Company’s common stock on the date of grant is based on the weighted average of the Company’s historical volatility as a public company, the implied volatility of publicly-traded options on the Company’s common stock and the volatilities of publicly traded peer companies that are reasonably comparable to the Company’s own operations;

⁽³⁾ The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant for zero coupon U.S. Treasury notes with maturities approximately equal to the expected term of the grant; and

⁽⁴⁾ The expected dividend yield is assumed to be zero as the Company has never paid dividends and has no current plans to pay any dividends on the Company’s common stock.

Schedule of Stock Option Activity

The following table summarizes the Company’s stock option activity:

	Stock options outstanding			Weighted average exercise price
Outstanding at December 31, 2020		279,021		$	25.55
Exercised		(105,889	)		27.83
Forfeited		(6,900	)		37.19
Outstanding at September 30, 2021		166,232			23.61

Schedule of Stock Options Outstanding, Vested and Expected to Vest and Exercisable

Stock options outstanding, vested and expected to vest and exercisable are as follows:

	As of September 30, 2021
	Number of shares		Remaining contractual life (years)		Weighted- average exercise price
Outstanding		166,232		5.33	$	23.61
Vested and expected to vest		166,088		5.33		23.60
Exercisable		147,478		5.17		21.38

Schedule of Vested and Nonvested Stock Option Activity

Vested and nonvested stock option activity was as follows:

	Vested				Nonvested
	Options outstanding		Weighted average exercise price		Options outstanding		Weighted average exercise price
Outstanding at September 30, 2021		147,478	$	21.38		18,754	$	41.22

Summary of RSU and PSU Activity

The following table summarizes the Company’s RSU and PSU activity:

	Number of Shares
Outstanding at December 31, 2020		1,420,541
Granted		641,442
Vested		(307,889	)
Forfeited		(135,266	)
Outstanding at September 30, 2021		1,618,828

Summary of Stock-Based Compensation Expense

The Company recorded the total stock-based compensation expense as follows (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2021		2020		2021		2020
Cost of revenue	$	1,260	$	842	$	3,078	$	2,153
Sales and marketing		5,747		4,395		15,068		11,920
Research and development		3,106		2,571		7,696		6,743
General and administrative		7,328		5,543		19,789		14,123
Total	$	17,441	$	13,351	$	45,631	$	34,939