Revenue Recognition - Disaggregated Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregated revenue	$ 2,014	$ 1,339	$ 4,202	$ 1,907
Product revenue
Disaggregated revenue	0	45	0	45
Royalty revenue
Disaggregated revenue	0	106	11	203
Contract revenue
Disaggregated revenue	2,014	1,188	4,191	1,659
Transferred at Point in Time
Disaggregated revenue	57	351	167	705
Transferred at Point in Time | Product revenue
Disaggregated revenue	0	45	0	45
Transferred at Point in Time | Royalty revenue
Disaggregated revenue	0	106	11	203
Transferred at Point in Time | Contract revenue
Disaggregated revenue	57	200	156	457
Transferred over Time
Disaggregated revenue	1,957	988	4,035	1,202
Transferred over Time | Product revenue
Disaggregated revenue	0	0	0	0
Transferred over Time | Royalty revenue
Disaggregated revenue	0	0	0	0
Transferred over Time | Contract revenue
Disaggregated revenue	$ 1,957	$ 988	$ 4,035	$ 1,202