Revenue Recognition - Disaggregated Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregated revenue	$ 1,851	$ 2,188
Product revenue
Disaggregated revenue	199	0
License and royalty revenue
Disaggregated revenue	0	11
Contract Revenue
Disaggregated revenue	1,652	2,177
Transferred at Point in Time
Disaggregated revenue	215	110
Transferred at Point in Time | Product revenue
Disaggregated revenue	199	0
Transferred at Point in Time | Royalty revenue
Disaggregated revenue	0	11
Transferred at Point in Time | Contract Revenue
Disaggregated revenue	16	99
Transferred over Time
Disaggregated revenue	1,636	2,078
Transferred over Time | Product revenue
Disaggregated revenue	0	0
Transferred over Time | Royalty revenue
Disaggregated revenue	0	0
Transferred over Time | Contract Revenue
Disaggregated revenue	$ 1,636	$ 2,078