Stockholders' Equity - Redeemable Convertible Preferred Stock (Details) - $ / shares	1 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Conversion of redeemable convertible preferred stock in connection with initial public offering (in shares)	41,628,207
IPO
Class of Stock [Line Items]
Offering price (in dollars per share)	$ 23.00
Series G Redeemable Convertible Preferred Stock
Class of Stock [Line Items]
Outstanding warrants to purchase Series G redeemable preferred stock (in shares)	933,269
Conversion of Redeemable Convertible Preferred Stock
Class of Stock [Line Items]
Conversion of redeemable convertible preferred stock in connection with initial public offering (in shares)			41,628,207
Class B Common Stock | Common Stock
Class of Stock [Line Items]
Conversion of convertible stock (in shares)		(43,255,565)	42,188,624
Class B Common Stock | Conversion of Redeemable Convertible Preferred Stock | Common Stock
Class of Stock [Line Items]
Conversion of convertible stock (in shares)	42,188,624
Class B Common Stock | Conversion of Warrants | Common Stock
Class of Stock [Line Items]
Conversion of convertible stock (in shares)	997,193