Note 11 - Stockholders' Equity (Deficit) - Outstanding Warrants (Details) - $ / shares	3 Months Ended		12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Warrants outstanding (in shares)			565,000	1,458,000	197,000
Warrants outstanding, weighted average exercise price (in dollars per share)			$ 1.81	$ 5.19	$ 35.23
Warrants granted (in shares)				3,087,000	1,317,000
Warrants granted, weighted average exercise price (in dollars per share)				$ 1.91	$ 7.40
Warrants expired (in shares)				(3,000)	(56,000)
Warrants expired, weighted average exercise price (in dollars per share)				$ 78.13	$ 39
Warrants exercised (in shares)	(363,523)	(3,613,284)	(21,000)	(3,977,000)
Warrants exercised, weighted average exercise price (in dollars per share)			$ 1.81	$ 1.95
Warrants outstanding (in shares)	565,000		544,000	565,000	1,458,000
Warrants outstanding, weighted average exercise price (in dollars per share)	$ 1.81		$ 1.81	$ 1.81	$ 5.19