Note 7 - Convertible Preferred Stock and Common Stock Warrants - Warrants Outstanding to Acquire Shares of its Common Stock (Details)	Jun. 30, 2017 $ / shares shares
Common stock warrants, outstanding (in shares) | shares	14,013,608
Exercise price (in dollars per share) | $ / shares	$ 2.22
Minimum [Member]
Exercise price (in dollars per share) | $ / shares	20
Maximum [Member]
Exercise price (in dollars per share) | $ / shares	$ 750
Convertible Preferred Stock Issued Prior to Merger [Member]
Common stock warrants, outstanding (in shares) | shares	457,721
Series A Convertible Preferred Stock [Member]
Common stock warrants, outstanding (in shares) | shares	13,555,887