Commitments and Contingencies - Service Agreements (Details) - USD ($) $ in Thousands		3 Months Ended
	Aug. 06, 2015	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2011
Service Agreements
Term of agreement	5 years
Amount required to pay for execution of the agreement				$ 151
Cost of goods sold
Service Agreements
Service agreement license fees		$ 488	$ 419