Note 4 - Investments (Details Textual) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	[1]
Available-for-sale Securities, Current	$ 500,000		$ 607,000
Marketable Securities, Unrealized Gain (Loss)	(77,000)	$ (96,000)
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax	(30,000)	(51,000)
Proceeds from Sale and Maturity of Marketable Securities	$ 0	$ 0

[1] The condensed consolidated balance sheet as of December 31, 2016 has been prepared using information from the audited consolidated balance sheet as of that date.