Note 8 - Stock Options - Exercise Price (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Outstanding at the end of the period (in shares) | shares	1,235
Options outstanding weighted average remaining contractual life (Year)	3 years 32 days
Options outstanding weighted average exercise price (in dollars per share)	$ 0.83
Options exercisable (in shares) | shares	1,172
Options exercisable weighted average exercise price (in dollars per share)	$ 0.84
Range 1 [Member]
Exercise price, low end of range (in dollars per share)	0.28
Exercise price, high end of range (in dollars per share)	$ 0.50
Outstanding at the end of the period (in shares) | shares	572
Options outstanding weighted average remaining contractual life (Year)	2 years 288 days
Options outstanding weighted average exercise price (in dollars per share)	$ 0.39
Options exercisable (in shares) | shares	533
Options exercisable weighted average exercise price (in dollars per share)	$ 0.39
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	361
Options outstanding weighted average remaining contractual life (Year)	2 years 189 days
Options outstanding weighted average exercise price (in dollars per share)	$ 0.68
Options exercisable (in shares) | shares	361
Options exercisable weighted average exercise price (in dollars per share)	$ 0.68
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	302
Options outstanding weighted average remaining contractual life (Year)	4 years 131 days
Options outstanding weighted average exercise price (in dollars per share)	$ 1.86
Options exercisable (in shares) | shares	278
Options exercisable weighted average exercise price (in dollars per share)	$ 1.92