Note 4 - Investments (Details Textual) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Available-for-sale Securities, Current	$ 551,000	$ 656,000	[1]
Proceeds from Sale and Maturity of Marketable Securities	0	0
Marketable Securities, Unrealized Gain (Loss)	(96,000)	(328,000)
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax	$ (51,000)	$ (205,000)

[1] The condensed consolidated balance sheet as of December 31, 2015 has been prepared using information from the audited consolidated balance sheet as of that date.