Long-term Debt (Details) - USD ($)	1 Months Ended	3 Months Ended	12 Months Ended
	May 31, 2017	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Payment of debt issuance costs			$ 633,000	$ 0	$ 0
Level 3
Debt Instrument [Line Items]
Long-term debt, fair value		$ 109,500,000	109,500,000
HCRP | Royalty-backed loan agreement
Debt Instrument [Line Items]
Proceeds from issuance of debt	$ 35,000,000	$ 65,000,000
Percentage revenue interest of future net sales	12.50%
Quarterly royalty payment (up to)	$ 15,000,000.0
Royalty percentage of future net sales	6.25%
Royalty trail cap, percentage of face amount	200.00%
Voluntary prepay election, amount due, percentage of funded amount	200.00%
Interest rate, stated percentage	11.00%
Contingent consideration, asset	$ 65,000,000.0
Unpaid interest payment added to principal amount, term	2 years 3 months
Accrued interest			4,400,000
Lender expense	$ 400,000
Payment of debt issuance costs	$ 800,000
Interest expense			$ 4,600,000
Effective interest rate	19.10%
HCRP | Royalty-backed loan agreement | December 2021
Debt Instrument [Line Items]
Royalty percentage of future net sales if principal and interest payments below minimum specified levels (up to)	17.50%
HCRP | Royalty-backed loan agreement | December 2022
Debt Instrument [Line Items]
Royalty percentage of future net sales if principal and interest payments below minimum specified levels (up to)	22.50%