Nature of the Business and Basis of Presentation (Details) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended
	Mar. 01, 2019	Feb. 04, 2019	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Liquidity
Accumulated deficit			$ 382,511		$ 356,092
Net losses			26,419	$ 65,821
Cash used in operations			31,796	63,256
Cash, cash equivalents and short-term investments			$ 204,206
Over-allotment | Class A common shares
Nature of the Business and Basis of Presentation
Issuance of stock (in shares)	161,126
Share price (in dollars per share)	$ 18.26
Gross proceeds from offering	$ 2,942
Follow-On Public Offering and Private Placement
Nature of the Business and Basis of Presentation
Aggregate proceeds from offerings net of underwriter discounts and commissions and other offering costs	$ 82,988
Follow-On Public Offering and Private Placement | Common Class A and Class A1 common shares
Nature of the Business and Basis of Presentation
Gross proceeds from offering		$ 85,000
Follow-On Offering | Class A common shares
Nature of the Business and Basis of Presentation
Issuance of stock (in shares)		2,654,984
Share price (in dollars per share)		$ 18.26
Gross proceeds from offering				$ 48,595
Private Placement | Class A1 common shares
Nature of the Business and Basis of Presentation
Issuance of stock (in shares)		2,000,000
Share price (in dollars per share)		$ 18.26