Note 12 - Stock Based Compensation - Stock Option Activity (Details) - The 2010 Stock Option and Incentive Plan [Member] - USD ($)	9 Months Ended
	Sep. 30, 2018
Outstanding, shares (in shares)	172,510
Outstanding, Weighted average exercise price per share (in dollars per share)	$ 49.27
Granted, shares (in shares)	611,668
Granted, Weighted average exercise price per share (in dollars per share)	$ 2.39
Forfeited, shares (in shares)	(417)
Forfeited, Weighted average exercise price per share (in dollars per share)	$ 5.64
Expired, shares (in shares)
Expired, Weighted average exercise price per share (in dollars per share)
Outstanding, shares (in shares)	783,761
Outstanding, Weighted average exercise price per share (in dollars per share)	$ 12.70
Outstanding, weighted average contractual life remaining in years (Year)	9 years 153 days
Outstanding, Aggregate intrinsic value
Exercisable, shares (in shares)	199,949
Exercisable, Weighted average exercise price per share (in dollars per share)	$ 40.62
Exercisable, weighted average contractual life remaining in years (Year)	8 years 346 days
Exercisable, Aggregate intrinsic value
Vested and expected to vest, shares (in shares)	783,761
Vested and expected to vest, Weighted average exercise price per share (in dollars per share)	$ 12.70
Vested and expected to vest, weighted average contractual life remaining in years (Year)	9 years 153 days
Vested and expected to vest, Aggregate intrinsic value