Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		19 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Net product sales	$ 1,520	$ 0	$ 1,520	$ 0
Collaboration revenue	1,340	$ 630	3,621	$ 1,699
Deferred revenue	11,200		11,200		$ 11,200
Other current assets
Disaggregation of Revenue [Line Items]
Deferred revenue	1,500		1,500		1,500
Fixed consideration
Disaggregation of Revenue [Line Items]
Performance obligation at inception of arrangement	20,000		20,000		20,000	$ 20,000
Portion of fixed consideration received					17,000
Variable consideration | Achievement of regulatory milestones
Disaggregation of Revenue [Line Items]
Amount that can be earned upon achievement of milestone	66,000		66,000		66,000
Variable consideration | Achievement of net sales milestones
Disaggregation of Revenue [Line Items]
Amount that can be earned upon achievement of net sales milestone	$ 42,500		$ 42,500		$ 42,500