Note 7 - Stockholders' Equity - Schedule of Warrants (Details)	9 Months Ended
	Sep. 30, 2018 $ / shares shares
Class of Warrant or Right, Outstanding (in shares) | shares	4,318,475
The 2014 Public Offering [Member]
Class of Warrant or Right, Outstanding (in shares) | shares	6,483
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | $ / shares	$ 540
Expiration Dates of Class of Warrant or Right	January 29, 2019
Placement Agent Fee [Member]
Class of Warrant or Right, Outstanding (in shares) | shares	1,106
Expiration Dates of Class of Warrant or Right	November 4, 2018
Placement Agent Fee [Member] | Minimum [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | $ / shares	$ 381.60
Placement Agent Fee [Member] | Maximum [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | $ / shares	$ 540
The 2017 Warrant B Private Placement [Member]
Class of Warrant or Right, Outstanding (in shares) | shares	441,670
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | $ / shares	$ 3.78
Expiration Dates of Class of Warrant or Right	December 22, 2018
The 2018 Warrants [Member]
Class of Warrant or Right, Outstanding (in shares) | shares	3,869,216
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | $ / shares	$ 4.05
Expiration Dates of Class of Warrant or Right	May 30, 2022