Licensing Agreements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Licensing Agreements
Licensing payments under agreements	$ 32	$ 1,400	$ 2,000
Augusta University Research Institute under AURI IDO
Licensing Agreements
Aggregate potential milestone payment per licensed product		2,800
Public Health Agency of Canada
Licensing Agreements
Aggregate potential milestone payment per licensed product		$ 250