Note 4 - Available-for-Sale Marketable Securities (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2015
Marketable Securities [Member]
Cost basis	$ 543,000	$ 502,000
Gains previously recognized on warrants	380,000	380,000
Loss included in accumulated other comprehensive income (loss)	(349,000)	(226,000)
Available-for-sale Securities, Current	574,000	656,000
Available-for-sale Securities, Current	$ 574,000	$ 656,000	[1]

[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.