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, 2017	Dec. 31, 2016
Outstanding at beginning of year (in shares)	21,277,479	17,806,472
Outstanding at beginning of year (in dollars per share)	$ 0.87	$ 1
Stock options granted (in shares)	35,810,289	3,771,488
Granted (in dollars per share)	$ 0.06	$ 0.24
Exercised (in shares)
Exercised (in dollars per share)
Forfeited (in shares)	(30,000)	(300,481)
Forfeited (in dollars per share)		$ 0.83
Outstanding at end of year (in shares)	57,057,768	21,277,479
Outstanding at end of year (in dollars per share)	$ 0.36	$ 0.87