Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2021

Equity [Abstract]

Schedule of Shares of Common Stock Reserved for Future Issuance

As of December 31, 2021, shares of common stock reserved for future issuance are as follows (in thousands):

Stock options, RSUs and PSUs outstanding	23,922
Shares available for future grant under the 2017 Performance Incentive Plan	1,142
Shares available for issuance under the employee stock purchase plan	1,043
Total common stock reserved for issuance	26,107

The following table lists the Black-Scholes option-pricing model assumptions used to calculate the fair value of employee and director stock options, as well as the resulting grant-date fair value:

	Year Ended December 31,
	2021			2020			2019
Average risk-free interest rate	1.2		%	0.4		%	1.8		%
Dividend yield	0.0		%	0.0		%	0.0		%
Average volatility factor	63.8		%	64.1		%	62.2		%
Weighted-average expected life	5.5 years			5.6 years			5.6 years
Weighted-average grant-date fair value of options granted	$	8.07		$	10.70		$	12.25