Organization - Narrative (Details) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020 USD ($) product	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Sep. 30, 2020 USD ($) segment product	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of therapy products | product	2						2
Number of reportable segments | segment							1
Net (loss) income	$ 3,618	$ (8,269)	$ (4,705)	$ 3,470	$ (19,792)	$ (2,844)	$ (9,356)	$ (19,166)
Accumulated deficit	388,035						388,035		$ 378,679
Cash and cash equivalents	43,507			$ 36,900			43,507	$ 36,900	$ 26,889
Short term investments	$ 42,000						$ 42,000