Stock-Based Compensation - Schedule of Stock Options (Details) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares
Number of options outstanding
Options outstanding at beginning of period (in shares) | shares	39,161,438
Awards granted and awarded (in shares) | shares	6,951,470
Options exercised (in shares) | shares	(5,649,135)
Options forfeited and canceled (in shares) | shares	(647,791)
Options vested and expected to vest (in shares) | shares	39,815,982
Options outstanding at end of period (in shares) | shares	39,815,982	39,161,438
Options exercisable (in shares) | shares	27,783,097
Weighted- average exercise price (Per share)
Weighted-average exercise price of options outstanding at beginning of period (in USD per share) | $ / shares	$ 1.93
Weighted-average exercise price of options granted (in USD per share) | $ / shares	10.28
Weighted-average exercise price of options exercised (in USD per share) | $ / shares	1.52
Weighted-average exercise price of options forfeited and canceled (in USD per share) | $ / shares	6.20
Weighted-average exercise price of options outstanding at end of period (in USD per share) | $ / shares	3.38	$ 1.93
Weighted-average exercise price of options vested and expected to vest (in USD per share) | $ / shares	3.38
Weighted-average exercise price of options exercisable (in USD per share) | $ / shares	$ 1.80
Weighted-average remaining contractual term of options outstanding (in years)	5 years 11 months 1 day	5 years 10 months 20 days
Weighted-average remaining contractual term of options vested and expected to vest (in years)	5 years 11 months 1 day
Weighted-average remaining contractual term of options exercisable (in years)	4 years 7 months 20 days
Aggregate intrinsic value of shares outstanding | $	$ 1,061,145	$ 347,574
Aggregate intrinsic value of options vested and expected to vest | $	1,061,145
Aggregate intrinsic value of shares exercisable | $	$ 784,263