Note I - Net Loss Per Share - Anti-dilutive Securities (Details) - shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Antidilutive securities (in shares)	14,405,932	12,450,670
Warrants to Purchase Common Stock [Member]
Antidilutive securities (in shares)	2,527,763	2,027,763
Share-based Payment Arrangement [Member]
Antidilutive securities (in shares)	5,117,655	3,631,496
Convertible Debt Securities [Member]
Antidilutive securities (in shares)	1,166,998	1,750,497
2021 Notes [Member]
Antidilutive securities (in shares)	4,481,182	5,040,914
Series A Convertible Preferred Stock [Member]
Antidilutive securities (in shares)	1,112,334