Common Stock - Narrative (Details)	Sep. 30, 2019 vote $ / shares shares	Dec. 31, 2018 $ / shares shares
Class A common stock
Class of Stock [Line Items]
Common stock, number of votes per share | vote	1
Common stock, shares authorized (in shares)	2,250,000,000	550,000,000
Common stock, par value (in dollars per share) | $ / shares	$ 0.001	$ 0.001
Common stock, shares issued (in shares)	86,838,606	0
Common stock, shares outstanding (in shares)	86,838,606	0
Class B common stock
Class of Stock [Line Items]
Common stock, number of votes per share | vote	10
Common stock, shares authorized (in shares)	315,000,000	300,000,000
Common stock, par value (in dollars per share) | $ / shares	$ 0.001	$ 0.001
Common stock, shares issued (in shares)	213,308,441	91,542,243
Common stock, shares outstanding (in shares)	213,308,441	91,542,243