Summary of Significant Accounting Policies (Reconciliation of Net Income (Loss) Reported in Financial Statements and Federal Tax Return) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Summary of Significant Accounting Policies [Abstract]
Net income (loss) per financial statements	$ 99	$ (170)
Adjustment to depreciation expense	(1,983)	(2,049)
Provision for losses and doubtful accounts		(18)
Adjustments to revenues	(427)	(68)
Other	13	(5)
Loss per federal tax return (unaudited)	$ (2,298)	$ (2,310)