Nature of Operations And Accounting Policies (Summary of Contract Liabilities) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Change in Contract with Customer, Liability [Roll Forward]
Balance at beginning of period	$ 794	$ 968
Previously deferred revenues recognized upon completion of performance obligations during the period	(794)	(968)
Net contract liabilities arising during the period	596	794
Balance at end of period	$ 596	$ 794