Summary of Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2018

Summary of Significant Accounting Policies [Abstract]

Inventory, Major Classes, Policy [Policy Text Block]

	As of June 30,		As of December 31,
	2018		2017
	(in thousands)
Raw materials	$	961	$	616
Work-in-process	131		149
Finished goods	1,050		1,183
Total inventory	$	2,142	$	1,948