v3.21.2
Stockholders' Equity (Tables)
 6 Months Ended
Jun. 30, 2021
Equity [Abstract]  
Summary of Stock Options and SAR Activity
A summary of stock option and SAR activity for the six months ended June 30, 2021 is as follows (in millions, except share amounts which are reflected in thousands, per share amounts, and years):
SARs Outstanding Number of SARsOptions Outstanding Number of SharesWeighted-Average Exercise Price Per ShareWeighted-Average Remaining Contractual Life (in years)Aggregate Intrinsic Value
As of December 31, 2020229 28,734 $12.87 4.97$1,104 
Granted— 945 $14.68 
Exercised(48)(6,177)$12.30 
Canceled and forfeited(2)(300)$18.24 
As of June 30, 2021179 23,202 $13.03 4.02$867 
Vested and expected to vest as of June 30, 2021138 17,773 $8.39 3.45$752 
Exercisable as of June 30, 2021138 17,773 $8.39 3.45$752 
Schedule of Restricted Stock Units Activity
The following table summarizes the activity related to our RSUs for the six months ended June 30, 2021 (in thousands, except per share amounts):
Number of SharesWeighted-Average
 Grant-Date Fair
 Value per Share
Unvested and outstanding as of December 31, 202083,736 $34.17 
Granted24,573 $58.35 
Vested(18,467)$36.67 
Canceled and forfeited(14,956)$36.45 
Unvested and outstanding as of June 30, 202174,886 $41.07 
Schedule of Stock-Based Compensation Expense by Function The following table summarizes total stock-based compensation expense by function for the three and six months ended June 30, 2020 and 2021 (in millions):
Three Months Ended June 30,Six Months Ended June 30,
2020202120202021
Operations and support$11 $38 $36 $65 
Sales and marketing10 19 24 42 
Research and development72 149 239 282 
General and administrative38 66 109 164 
Total$131 $272 $408 $553