Marketable Securities (Details) - USD ($)	Dec. 31, 2021	Dec. 31, 2020
Fair Value [Member]
Other Investment Not Readily Marketable [Line Items]
Fixed income mutual funds	$ 14,325,000	$ 11,335,000
Corporate bonds and notes	801,000	4,490,000
Total marketable securities	15,126,000	19,366,000
Certificates of deposit		3,541,000
Cost Basis [Member]
Other Investment Not Readily Marketable [Line Items]
Fixed income mutual funds	14,462,000	11,255,000
Corporate bonds and notes	813,000	4,500,000
Total marketable securities	15,275,000	19,289,000
Certificates of deposit		3,534,000
Gross Unrealized Gains [Member]
Other Investment Not Readily Marketable [Line Items]
Fixed income mutual funds		80,000
Corporate bonds and notes		18,000
Total marketable securities		105,000
Certificates of deposit		7,000
Gross Unrealized Losses [Member]
Other Investment Not Readily Marketable [Line Items]
Fixed income mutual funds	(137,000)
Corporate bonds and notes	(12,000)	(28,000)
Total marketable securities	$ (149,000)	(28,000)
Certificates of deposit