Note 3 - Basis of Presentation and Summary of Significant Accounting Policies - Outstanding Dilutive Securities (Details) - shares	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Anti-dilutive securities (in shares)	34,526,309	14,214,066
Convertible Debt Securities [Member]
Anti-dilutive securities (in shares)		774,886
Series A Convertible Preferred Stock [Member]
Anti-dilutive securities (in shares)		10,449,338
Warrant [Member]
Anti-dilutive securities (in shares)	31,312,512	457,721
Employee Stock Option [Member]
Anti-dilutive securities (in shares)	3,213,797	2,525,989
Restricted Stock [Member]
Anti-dilutive securities (in shares)		6,132