Note 3 - Investments (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Available-for-sale Securities, Current, Total	$ 335,000	$ 258,000	[1]
Debt Securities, Available-for-sale, Realized Gain (Loss), Total	231,000	(50,000)
Debt Securities, Available-for-sale, Realized Loss	170,000	57,000
Debt Securities, Available-for-sale, Realized Gain	$ 61,000	7,000
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, after Tax		57,000
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, Tax		$ 7,000

[1] The condensed consolidated balance sheet as of December 31, 2018 has been prepared using information from the audited consolidated balance sheet as of that date.