Summary of Significant Accounting Policies Concentration of Sales to Major Customers) (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Total revenue	$ 395	$ 639	$ 587	$ 1,469	$ 4,605	$ 1,190	$ 1,240	$ 1,851	$ 3,090	$ 8,886
Customer Revenue Concentration
Total revenue									$ 3,000	$ 7,700
Concentration Risk, Percentage									97.00%	86.00%
Second Commercial Customer
Total revenue										$ 1,200
Concentration Risk, Percentage										13.00%