Summary of Significant Accounting Policies - Revenue Recognition (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Revenue Recognition
Sales return period prior to expiry date			6 months
Sales return period subsequent to expiry date			12 months
Royalty Revenue
Non-recourse liability related to sale of future royalties					$ 30,000,000
Royalty revenues	$ 1,140,000	$ 776,000	$ 3,464,000	$ 2,007,000
Interest expense-non-recourse royalty liability	1,004,000	998,000	3,564,000	2,530,000
Milestone revenues recorded	$ 0	$ 0	$ 0	$ 750,000