Share Based Compensation - Options (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Aggregate Intrinsic Value
Proceeds from exercise of options	$ 1,119	$ 377
Class A common shares | Stock options
Number of Shares
Outstanding, beginning of the period	5,960,939
Granted	3,608,588
Exercised	(150,253)	(25,683)
Forfeited	(927,540)
Outstanding, end of the period	8,491,734	5,960,939
Options exercisable	3,373,659
Options unvested	5,118,075
Weighted Average Exercise Price
Outstanding, beginning of the period	$ 10.25
Granted	13.44
Exercised	3.93
Forfeited	15.26
Outstanding, end of the period	11.17	$ 10.25
Options exercisable	7.29
Options unvested	$ 13.74
Weighted Average Remaining Contractual Term (in years)
Outstanding	7 years 10 months 17 days	8 years 6 months 22 days
Exercisable	6 years 2 months 27 days
Unvested	8 years 11 months 16 days
Aggregate Intrinsic Value
Outstanding	$ 27,217	$ 108,352
Exercisable	19,903
Unvested	7,314
Intrinsic value of options exercised	1,776	411
Proceeds from exercise of options	$ 590	$ 87
Weighted-average grant-date fair value per share of options granted	$ 9.36	$ 11.96
Total fair value of options vested	$ 13,997	$ 2,255