Concentration of Sales to Major Customers (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Customer Revenue Concentration
Total revenue	$ 2,000	$ 769	$ 4,000	$ 973
Concentration Risk, Percentage	97.00%	57.00%	96.00%	51.00%
Second Commercial Customer
Total revenue		$ 227		$ 442
Concentration Risk, Percentage		17.00%		23.00%
Third Commercial Customer
Total revenue		$ 107		$ 204
Concentration Risk, Percentage		8.00%		11.00%
Accounts Receivable Concentration
Accounts receivable	$ 2,700		$ 2,700
Concentration Risk, Percentage			100.00%