Note 11 - Stock Options and Restricted Stock - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016
Outstanding (in shares)	4,814,434	4,211,168
Outstanding, weighted average exercise price (in dollars per share)	$ 0.71	$ 1.09
Outstanding, weighted average remaining contractual life (Year)	2 years 197 days	3 years 167 days		2 years 310 days
Outstanding, aggregate intrinsic value	$ 93	$ 1,007		$ 46
Granted (in shares)	0	2,971,600
Granted, weighted average exercise price (in dollars per share)		$ 0.32
Exercised (in shares)	(1,230,002)	0
Exercised, weighted average exercise price (in dollars per share)	$ 0.44
Forfeited or Expired (in shares)	(1,039,767)	(2,368,334)	[1]
Forfeited or Expired, weighted average exercise price (in dollars per share)	$ 0.71	$ 0.90
Outstanding (in shares)	2,544,665	4,814,434		4,211,168
Outstanding, weighted average exercise price (in dollars per share)	$ 0.85	$ 0.71		$ 1.09
Vested at December 31, 2018 (in shares)	1,950,832
Vested at December 31, 2018, weighted average exercise price (in dollars per share)	$ 1
Vested at December 31, 2018, weighted average remaining contractual life (Year)	2 years 105 days
Vested at December 31, 2018, aggregate intrinsic value	$ 64
Exercisable (in shares)	1,950,832
Exercisable, weighted average exercise price (in dollars per share)	$ 1
Exercisable, weighted average remaining contractual life (Year)	2 years 105 days
Exercisable, aggregate intrinsic value	$ 64

[1] 1,230,002 shares exercised using the cashless option resulted in 663,938 shares of common stock being issued.