Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Other Income and Expenses [Abstract]
Interest expense	$ (4,792)	$ (4,253)	$ (9,485)	$ (8,972)
Interest expense on nonrecourse liability related to sale of future royalties	(1,023)	(1,136)	(2,085)	(2,296)
Total	(5,815)	(5,389)	(11,570)	(11,268)
Non-cash interest expense	$ 4,200	$ 3,900	$ 8,179	$ 7,748