Note 13 - Warrants - Summary of Warrant Activity (Details)	9 Months Ended
	Sep. 30, 2017 USD ($) $ / shares shares
Warrants outstanding (in shares) | shares	1,487,958
Warrants outstanding (in dollars per share) | $ / shares	$ 9.39
Warrants issued during the nine months ended September 30, 2017 (see Note 10) (in shares) | shares	6,679,378
Warrants issued during the nine months ended September 30, 2017 (see Note 10) (in dollars per share) | $ / shares	$ 3.08
Warrants exercised during the nine months ended September 30, 2017 (see Note 10) (in shares) | shares	(2,638,702)
Warrants exercised during the nine months ended September 30, 2017 (see Note 10) (in dollars per share) | $ / shares	$ 1.92
Warrants outstanding (in shares) | shares	5,528,634
Warrants outstanding (in dollars per share) | $ / shares	$ 5.33
Aggregate intrinsic value of outstanding warrants | $
Weighted average remaining contractual terms (Year)	3 years 58 days