Stock-Based Compensation and Employee Benefit Plan - Employee Stock Purchase Plan (Details)		12 Months Ended
	Jul. 25, 2018 shares	Dec. 31, 2020 USD ($) shares	Dec. 31, 2019 USD ($) shares	Apr. 30, 2018 shares
Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of share maximum per employee		2,500
Share-Based Compensation Arrangement By Share-based Payment Award, Purchase Period		6 months
Share-based Compensation Arrangement by Share-based Payment Award, Maximum Employee Subscription Amount | $		$ 25,000
2018 ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee stock ownership plan (ESOP), compensation expense | $		$ 5,700,000	$ 10,300,000
Share-based compensation arrangement by share-based payment award, shares issued in period		1,937,825
Number of additional shares authorized (in shares)		1,494,819
Number of common stock reserved for issuance (in shares)		2,587,401
Unrecognized stock-based compensation cost | $		$ 1,700,000
Expense expected to be recognized over a weighted-average period		3 months 18 days
Shares reserved for future issuance (in shares)		2,587,874	3,030,407
2018 ESPP | Employee Stock | Class A common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock reserved for issuance (in shares)				33,333,333
Shares reserved for future issuance (in shares)	3,333,333
Employee Purchase Plan, Number Of Share Reserved For Issuance Increase, Term	9 years
Employee Purchase Plan, Percentage Of Total Outstanding Shares	0.01
Purchase price of common stock, percentage of fair market value		85.00%