Fair Value of Financial Instruments (Details) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Cost	$ 35,746,000
Unrealized Gains	0
Unrealized Losses	(33,000)
Fair Value	35,713,000
Cash and Cash Equivalents [Member]
Cost	9,682,000	$ 5,297,000
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	9,682,000	$ 5,297,000
Short term Investments [Member]
Cost	26,064,000
Unrealized Gains	0
Unrealized Losses	(33,000)
Fair Value	$ 26,031,000