Note 4 - Investments - Available-for-sale Marketable Securities (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Gains previously recognized on warrants	$ 380,000	$ 380,000
Loss included in accumulated other comprehensive loss before tax benefit	(671,000)	(316,000)
Available-for-sale Securities, Current	252,000	607,000	[1]
Marketable Securities [Member]
Cost basis	543,000	543,000
Available-for-sale Securities, Current	$ 252,000	$ 607,000

[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.