Note 10 - Per Share Data (Details Textual) - shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Employee Stock Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	59,825,123	20,540,769
Warrant [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	18,313,373	3,744,623
Convertible Debt Securities [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	94,651,255	40,677,826