Stockholders' Deficit (Details)	9 Months Ended	60 Months Ended
	Sep. 30, 2019 vote $ / shares shares	Sep. 30, 2019 $ / shares shares	Dec. 31, 2018 $ / shares shares
Stockholders' Equity
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, par value (in dollars per share) | $ / shares	$ 0.001	$ 0.001
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Class A common stock
Stockholders' Equity
Common stock, shares authorized (in shares)	500,000,000	500,000,000	500,000,000
Common stock, par value (in dollars per share) | $ / shares	$ 0.001	$ 0.001	$ 0.001
Common stock, shares outstanding (in shares)	65,502,165	65,502,165	62,329,701
Number of votes each holder is entitled | vote	1
Class B common stock
Stockholders' Equity
Common stock, shares authorized (in shares)	164,000,000	164,000,000	164,000,000
Common stock, par value (in dollars per share) | $ / shares	$ 0.001	$ 0.001	$ 0.001
Common stock, shares outstanding (in shares)	27,372,273	27,372,273	28,417,882
Number of votes each holder is entitled | vote	10
Conversion ratio following the completion of the offering	1
Conversion ratio upon transfer	1
Number of shares converted into Class A common stock (in shares)		54,667,389
Class B common stock | Maximum
Stockholders' Equity
Aggregate number of shares outstanding Class A common stock and Class B common stock that shall convert automatically (less than)	10.00%
Class B common stock | Minimum
Stockholders' Equity
Percentage of outstanding shares of Class B common stock that shall convert automatically in the event of the affirmative vote or written consent of holders	66.67%