Note 9 - Stock Options - Exercise Price (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2017 $ / shares shares
Outstanding at the end of the period (in shares) | shares	1,746
Options outstanding weighted average remaining contractual life (Year)	3 years 10 days
Options outstanding weighted average exercise price (in dollars per share)	$ 0.68
Options exercisable (in shares) | shares	1,662
Options exercisable weighted average exercise price (in dollars per share)	$ 0.68
Range 1 [Member]
Exercise price, low end of range (in dollars per share)	0.20
Exercise price, high end of range (in dollars per share)	$ 0.50
Outstanding at the end of the period (in shares) | shares	985
Options outstanding weighted average remaining contractual life (Year)	2 years 189 days
Options outstanding weighted average exercise price (in dollars per share)	$ 0.34
Options exercisable (in shares) | shares	914
Options exercisable weighted average exercise price (in dollars per share)	$ 0.34
Range 2 [Member]
Exercise price, low end of range (in dollars per share)	0.51
Exercise price, high end of range (in dollars per share)	$ 1
Outstanding at the end of the period (in shares) | shares	481
Options outstanding weighted average remaining contractual life (Year)	2 years 357 days
Options outstanding weighted average exercise price (in dollars per share)	$ 0.65
Options exercisable (in shares) | shares	481
Options exercisable weighted average exercise price (in dollars per share)	$ 0.65
Range 3 [Member]
Exercise price, low end of range (in dollars per share)	1.01
Exercise price, high end of range (in dollars per share)	$ 2.73
Outstanding at the end of the period (in shares) | shares	280
Options outstanding weighted average remaining contractual life (Year)	4 years 343 days
Options outstanding weighted average exercise price (in dollars per share)	$ 1.92
Options exercisable (in shares) | shares	267
Options exercisable weighted average exercise price (in dollars per share)	$ 1.90