Stock-based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	Aug. 31, 2021	Feb. 28, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense			$ 34,725	$ 10,868	$ 91,828	$ 19,362
Exercised options, right to repurchase, options lapsed, typical percentage					25.00%
Liabilities related to exercised options subject to repurchase					$ 2,400		$ 100
Employee promissory note settled in shares		$ 17,200
Employee promissory note settled in cash		3,700
Restricted Stock Units (RSUs)
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Number of shares stock option (in shares)			870,410		6,908,924
Restricted stock units granted (in dollars per share)			$ 58.92		$ 58.60
Promissory Notes
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Employee promissory note settled		$ 20,900
Employee promissory note outstanding			$ 15,100		$ 15,100		$ 40,400
Tranche One
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Exercised options, right to repurchase, term					1 year
Tranche Two
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Exercised options, right to repurchase, term					36 months
Minimum | Restricted Stock Units (RSUs)
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Restricted stock unit, granted, vesting period					4 years
Maximum | Restricted Stock Units (RSUs)
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Restricted stock unit, granted, vesting period					5 years
Class A Common Stock
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Number of shares recognized cost (in shares)		60,968
Number of share options exercised (in shares)			2,884,999		2,884,999		8,022,499
Class A Common Stock | Promissory Notes
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Early exercised options with promissory note (in shares)					841,563		4,136,677
Class A Common Stock | Equity Option
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Exercised options subject to repurchase (in shares)					879,600		19,800
2021 Equity Incentive Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Capital shares reserved for future issuance (in shares)			39,000,000		39,000,000
Share based compensation by share based payment arrangement increase in the number of shares available for future issuance (in shares)					39,000,000
Share based compensation by share based payment arrangement increase in the number of shares available for future issuance as a percentage of outstanding stock					5.00%
2021 Partner Studio Incentive Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Capital shares reserved for future issuance (in shares)			390,000		390,000
2021 Partner Studio Incentive Plan | Restricted Stock Units (RSUs)
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Number of shares stock option (in shares)	359,623
Restricted stock units granted (in dollars per share)	$ 57.19
2021 Partner Studio Incentive Plan | Minimum | Restricted Stock Units (RSUs)
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Restricted stock unit, granted, vesting period	4 years
2021 Partner Studio Incentive Plan | Maximum | Restricted Stock Units (RSUs)
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Restricted stock unit, granted, vesting period	5 years
Employee Stock Purchase Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period					24 months
Employee Stock Purchase Plan | Class A Common Stock
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share based compensation by share based payment arrangement increase in the number of shares available for future issuance as a percentage of outstanding stock					1.00%
Percentage of eligible compensation eligible for participation in the stock purchase plan			15.00%		15.00%
Share based compensation by share based payment arrangement purchase price of the stock as a percentage of fair value					85.00%
Share based compensation by share based payment arrangement maximum number of shares per employee (in shares)					590
Share based compensation by share based payment arrangement number of shares available for issuance (in shares)			7,800,000		7,800,000
Share based compensation by share based payment arrangement number of additional shares available for issuance (in shares)					7,800,000
2011 Equity Incentive Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense			$ 300		$ 900