Deferred Royalty Obligation (Details) - USD ($)		3 Months Ended		6 Months Ended
	May 10, 2018	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Debt Instrument [Line Items]
Deferred royalty obligation, net		$ 124,406,000		$ 124,406,000		$ 124,379,000
Interest expense		2,500,000	$ 2,800,000	4,900,000	$ 5,500,000
Royalty Obligation Payable		600,000		600,000
HealthCare Royalty Partners
Debt Instrument [Line Items]
Proceeds from royalty agreement	$ 125,000,000.0
Required payment for breach of agreement, payment one	125,000,000.0
Required payment for breach of agreement, payment two	225,000,000.0
HealthCare Royalty Partners | Loans Payable | Royalty Financing Agreement
Debt Instrument [Line Items]
Deferred royalty obligation, net	125,000,000.0	124,400,000		124,400,000
Debt issuance costs	$ 700,000
Unamortized debt discount		600,000		600,000
Accrued interest expense		18,800,000		18,800,000		15,500,000
Royalty payments		800,000		1,500,000
HealthCare Royalty Partners | Period One
Debt Instrument [Line Items]
Maximum potential royalty payout	10.00%
HealthCare Royalty Partners | Period Two
Debt Instrument [Line Items]
Increase in maximum potential payout percent	4.00%
HealthCare Royalty Partners | Payout Period
Debt Instrument [Line Items]
Increase in maximum potential payout percent	4.00%
Other Noncurrent Liabilities | HealthCare Royalty Partners | Loans Payable | Royalty Financing Agreement
Debt Instrument [Line Items]
Accrued interest expense		$ 15,300,000		$ 15,300,000		$ 12,800,000