Liability Related to the Sale of Future Royalties (Details) - USD ($) $ in Thousands		3 Months Ended
	Mar. 22, 2019	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Nonmonetary Transaction [Line Items]
Proceeds from royalty interest purchase agreement with Oberland Capital Management, LLC		$ 0		$ 65,000
Payment towards debt obligations		0		$ 1,825
Transaction fees	$ 600
Non-cash interest rate (percent)	8.20%
Carrying value of liability related to the sale of future royalties at January 1, 2020	$ 65,000		$ 62,477
Amortization of capitalized issuance costs		15
Capitalized issuance costs			(584)
Imputed interest expense recognized for the three months ended March 31, 2020		1,283	4,055
Less: payments to Oberland Capital, LLC		(2,786)	(5,994)
Carrying value of liability related to the sale of future royalties at March 31, 2020		$ 60,989	$ 62,477
Oberland Capital
Nonmonetary Transaction [Line Items]
Proceeds from royalty interest purchase agreement with Oberland Capital Management, LLC	65,000
Cash proceeds from royalty purchase agreement	70,700
Purchaser default option period (days)		180 days
HealthCare Royalty Partners III, L.P.
Nonmonetary Transaction [Line Items]
Proceeds from royalty interest purchase agreement with Oberland Capital Management, LLC	27,500
Payment towards debt obligations	37,200
Repayment of debt, principal	33,800
Accrued and unpaid interest and prepayment fees	3,400
Transaction fees	300
Royalty Amounts in 2021 | Oberland Capital
Nonmonetary Transaction [Line Items]
Cash proceeds from royalty purchase agreement	17,200
Royalty amount threshold	18,000
Aggregate Net Royalties Prior to 2027 | Oberland Capital
Nonmonetary Transaction [Line Items]
Cash proceeds from royalty purchase agreement	53,500
Royalty amount threshold	$ 117,000