Note 7 - Stock-based Compensation and Option Plans - Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Weighted average value per option granted during the period (in dollars per share)	$ 1.87	$ 1.81	$ 0.68
Employee Stock Option [Member]
Balance (in shares)	8,317	8,154	6,808
Balance, weighted average exercise price (in dollars per share)	$ 2.35	$ 2.39	$ 2.89
Granted (in shares)	300	317	2,265
Granted, weighted average exercise price (in dollars per share)	$ 2.80	$ 1.81	$ 1.02
Exercised (in shares)	(379)	(5)	(83)
Exercised, weighted average exercise price (in dollars per share)	$ 1.71	$ 0.97	$ 1.40
Forfeited/Expired (in shares)	(689)	(149)	(836)
Forfeited/Expired, weighted average exercise price (in dollars per share)	$ 2.70	$ 3.58	$ 2.84
Balance (in shares)	7,549	8,317	8,154
Balance, weighted average exercise price (in dollars per share)	$ 2.37	$ 2.35	$ 2.39
Options outstanding, weighted average remaining life (Year)	4 years 328 days
Options outstanding, intrinsic value per share (in dollars per share)	$ 1.68
Exercisable at end of year (in shares)	6,479
Exercisable, weighted average remaining life (Year)	4 years 182 days
Exercisable, intrinsic value per share (in dollars per share)	$ 1.78
Weighted average value per option granted during the period (in dollars per share)	$ 1.87	$ 1.81	$ 0.68
Total fair value of options vested (000's)	$ 2,054	$ 2,795	$ 2,776
Total intrinsic value of options exercised (000's)	$ 395	$ 5	$ 39