Net Loss Per Share - Earnings Per Share Basic and Diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Denominator
Weighted-average common shares outstanding - basic and diluted (in shares)	48,171,552	46,166,660	47,858,628	45,700,559
Basic and diluted net loss per share (in dollars per share)	$ (0.41)	$ (0.18)	$ (0.63)	$ (0.35)
Class A Common Stock
Numerator
Net loss	$ (16,257)	$ (6,626)	$ (24,905)	$ (12,523)
Denominator
Weighted-average common shares outstanding - basic and diluted (in shares)	39,622,989	36,758,866	39,287,647	36,255,515
Basic and diluted net loss per share (in dollars per share)	$ (0.41)	$ (0.18)	$ (0.63)	$ (0.35)
Class B Common Stock
Numerator
Net loss	$ (3,508)	$ (1,696)	$ (5,433)	$ (3,262)
Denominator
Weighted-average common shares outstanding - basic and diluted (in shares)	8,548,563	9,407,794	8,570,981	9,445,044
Basic and diluted net loss per share (in dollars per share)	$ (0.41)	$ (0.18)	$ (0.63)	$ (0.35)