Long-term Debt - Narrative (Details)		3 Months Ended			9 Months Ended
	Sep. 12, 2019 USD ($) installment $ / shares shares	Sep. 30, 2019 USD ($) $ / shares	Sep. 12, 2019 USD ($) installment $ / shares shares	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) $ / shares	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Debt Instrument [Line Items]
Loss on extinguishment of debt		$ 7,155,000		$ 0	$ 7,155,000	$ 0
Senior Notes | Note Purchase Agreement
Debt Instrument [Line Items]
Debt maximum borrowing capacity	$ 150,000,000		$ 150,000,000
Debt face amount	80,000,000	80,000,000	80,000,000		80,000,000		$ 75,000,000
Debt amount to be issued	$ 70,000,000		$ 70,000,000
Stated interest rate	10.75%		10.75%
Debt principal payments, number of installments | installment	8		8
Debt upfront fee	$ 1,125,000		$ 1,125,000
Number of shares called by warrants | shares	810,357		810,357
Warrants exercise price (in USD per share) | $ / shares	$ 6.72		$ 6.72
Loans, term	5 years
Debt issuance costs	$ 4,836,000		$ 4,836,000
Fair value of warrants	$ 2,404,000
Debt issuance costs, additional as percentage of principal amount	0.50%		0.50%
Prepayment fee, after second and before third anniversary	2.00%		2.00%
Prepayment fee, after third and before fourth anniversary	1.00%		1.00%
Prepayment premium amount	$ 0		$ 0
Debt covenant, cash and cash equivalents		30,000			30,000
Interest expense		$ 2,372,000		$ 2,361,000	$ 7,148,000	$ 6,855,000
Senior Notes | Note Purchase Agreement - First Delayed Draw Notes
Debt Instrument [Line Items]
Debt amount to be issued	30,000,000		30,000,000
Senior Notes | Note Purchase Agreement - First Delayed Draw Notes | Quarter Ended December 31, 2019
Debt Instrument [Line Items]
Debt issuance criteria term, net sales and royalties benchmark	9,000,000
Senior Notes | Note Purchase Agreement - Second Delayed Draw Notes
Debt Instrument [Line Items]
Debt amount to be issued	20,000,000		20,000,000
Senior Notes | Note Purchase Agreement - Second Delayed Draw Notes | Quarter Ended March 31, 2020
Debt Instrument [Line Items]
Debt issuance criteria term, net sales and royalties benchmark	11,000,000
Senior Notes | Note Purchase Agreement - Second Delayed Draw Notes | Six Months Ended June 30, 2020
Debt Instrument [Line Items]
Debt issuance criteria term, net sales and royalties benchmark	25,000,000
Senior Notes | Note Purchase Agreement - Third Delayed Draw Notes
Debt Instrument [Line Items]
Debt amount to be issued	20,000,000		20,000,000
Senior Notes | Note Purchase Agreement - Third Delayed Draw Notes | Quarter Ended September 30, 2020
Debt Instrument [Line Items]
Debt issuance criteria term, net sales and royalties benchmark	14,500,000
Senior Notes | Note Purchase Agreement - Third Delayed Draw Notes | Six Months Ended December 31, 2020
Debt Instrument [Line Items]
Debt issuance criteria term, net sales and royalties benchmark	31,000,000
Senior Notes | Athyrium Senior Secured Notes
Debt Instrument [Line Items]
Prepayment premium amount	$ 3,669,000		3,669,000
Accrued and unpaid interest			$ 2,049,000
Exit fee (as a percent)	2.00%		2.00%
Loss on extinguishment of debt	$ 7,155,000
Warrants Expiring September 12, 2022
Debt Instrument [Line Items]
Warrants exercise price (in USD per share) | $ / shares		$ 6.72			$ 6.72