Summary of Significant Accounting Policies (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2018 USD ($) item	Dec. 31, 2017 USD ($)	Feb. 28, 2017 USD ($)
Summary of Significant Accounting Policies
PDUFA fee paid, later refunded			$ 2,000
Revenue Recognition
Revenue, Remaining Performance Obligation, Optional Exemption, Performance Obligation [true false]	true
Revenue, Practical Expedient, Financing Component [true false]	true
Number of active research grants | item	2
Remaining funds available to the Company under grants	$ 0
Inventory
Finished goods inventory	$ 1,044	$ 0