Note 10 - Options and Warrants to Purchase Common Stock - Summary of the Status and Changes of the Options Granted Under the Stock Option Plans and Other Agreements (Details) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Outstanding at beginning of period (in shares)	17,806,472	17,053,116
Outstanding at beginning of period (in dollars per share)	$ 1	$ 1.02
Issued (in shares)	3,771,488	988,355
Issued (in dollars per share)	$ 0.24	$ 0.63
Forfeited (in shares)	(300,481)	(235,000)
Forfeited (in dollars per share)	$ 0.83	$ 0.77
Outstanding at end of period (in shares)	21,277,479	17,806,472
Outstanding at end of period (in dollars per share)	$ 0.87	$ 1