Stockholders' Equity - Common Stock, Convertible Preferred Stock, Preferred Stock (Details)	1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Dec. 31, 2017 shares	Jun. 30, 2020 $ / shares shares	Jun. 30, 2019 shares	Jun. 30, 2020 vote $ / shares shares	Jun. 30, 2019 shares	Dec. 31, 2019 shares
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)		240,000,000.0		240,000,000.0
Restricted Stock
Class of Stock [Line Items]
Shares granted (in shares)				20,800,000
Co-Founder Grants | Restricted Stock
Class of Stock [Line Items]
Shares granted (in shares)	14,700,000			10,300,000		14,700,000
Class A common stock
Class of Stock [Line Items]
Votes per share | vote				1
Common stock, shares authorized (in shares)		2,400,000,000.0		2,400,000,000.0
Common stock, par value (in dollars per share) | $ / shares		$ 0.00001		$ 0.00001
Common stock, shares issued (in shares)		316,100,000		316,100,000		255,800,000
Common stock, shares outstanding (in shares)		316,100,000		316,100,000		255,800,000
Class B common stock
Class of Stock [Line Items]
Votes per share | vote				10
Shares converted in conversion (in shares)		53,500,000	25,900,000	63,400,000	37,700,000
Common stock, shares authorized (in shares)		475,000,000.0		475,000,000.0
Common stock, par value (in dollars per share) | $ / shares		$ 0.00001		$ 0.00001
Common stock, shares issued (in shares)		97,900,000		97,900,000		161,200,000
Common stock, shares outstanding (in shares)		97,900,000		97,900,000		161,200,000
Class C common stock
Class of Stock [Line Items]
Votes per share | vote				0
Common stock, shares authorized (in shares)		800,000,000.0		800,000,000.0
Common stock, par value (in dollars per share) | $ / shares		$ 0.00001		$ 0.00001
Common stock, shares issued (in shares)		0		0		0
Common stock, shares outstanding (in shares)		0		0		0