Summary of significant accounting policies and basis of presentation - Monetization of future royalties (Details) - USD ($) $ in Thousands				1 Months Ended		6 Months Ended		30 Months Ended
	Jun. 30, 2020	Jun. 08, 2020	Jan. 01, 2018	Jan. 31, 2018	Dec. 31, 2017	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Dec. 31, 2019
Liability related to sale of future royalties activity
Proceeds from sale of future royalties, net						$ 14,750
Accretion of interest expense on liability related to royalty monetization						4,385	$ 4,075
Net ending liability related to sale of future royalties	$ 64,351							$ 64,351	$ 48,714
HCR | Royalty Interest Acquisition Agreement
Summary Of Significant Accounting Policies
Maximum royalties under monetization agreement					$ 78,800
Milestone payment receivable					$ 15,000
Liability related to sale of future royalties activity
Liability related to the sale of future royalties - beginning balance						55,144
Proceeds from sale of future royalties, net	59,300	$ 14,800	$ 59,300	$ 44,500		14,750		59,300
Foreign currency translation gain						(239)
Accretion of interest expense on liability related to royalty monetization						4,385
Repayment of the liability						(7,778)
Liability related to sale of future royalties - ending balance	66,262					$ 55,144		66,262	$ 55,144
Less current portion classified within accrued expenses	(1,911)							(1,911)
Net ending liability related to sale of future royalties	$ 64,351							$ 64,351
Annual effective interest rate	20.40%							20.40%