Other Income (Expense) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Other Income and Expenses [Abstract]
Interest income	$ 5,777	$ 4,681
Interest expense	(4,693)	(4,710)
Interest expense on nonrecourse liability related to sale of future royalties	(1,062)	(1,160)
Total other income (expense)	22	(1,189)
Non-cash interest expense	$ 4,061	$ 3,848