Stock-based Compensation - Stock Option Activity (Details) - $ / shares	6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options outstanding, beginning balance (in shares)	4,189,292
Options granted (in shares)	160,948	1,348,290
Options exercised (in shares)	(75,098)	(24,845)
Options forfeited (in shares)	(112,420)	(74,903)
Options outstanding, ending balance (in shares)	4,162,722		4,189,292
Options exercisable (in shares)	1,516,598
Options vested and expected to vest (in shares)	4,162,722
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Options outstanding, weighted average exercise price per share, beginning balance (in dollars per share)	$ 10.31
Options outstanding, weighted average exercise price per share, ending balance (in dollars per share)	$ 10.38		$ 10.31
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Options outstanding, weighted average remaining contractual life (in years)	8 years 4 months 24 days		8 years 10 months 24 days