Note 7 - 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		6 Months Ended	12 Months Ended
		Jun. 30, 2017	Dec. 31, 2016
Outstanding, shares (in shares)		21,277,479
Outstanding, weighted average exercise price (in dollars per share)		$ 0.87
Outstanding, weighted average exercise price (in dollars per share)		$ 0.85	$ 0.87
Outstanding, weighted average remaining contractual life (Year)	[1]	3 years 354 days	4 years 94 days
Issued (in shares)		650,000
Issued, weighted average exercise price (in dollars per share)		$ 0.25
Issued, weighted average remaining contractual life (Year)	[1]	5 years
Forfeited (in shares)		30,000
Forfeited (in dollars per share)		$ 1.55
Outstanding, shares (in shares)		21,897,479	21,277,479
Exercisable, shares (in shares)		21,435,784
Exercisable, weighted average exercise price (in dollars per share)		$ 0.86
Exercisable, weighted average remaining contractual life (Year)	[1]	4 years 182 days

[1] Measured in years