Note 9 - Share Based Payments - Stock Options Exercisable and Expected to Vest (Details)	12 Months Ended
	Dec. 31, 2018 USD ($) $ / shares shares
Stock options exercisable, Options (in shares)	1,433,500
Stock options exercisable, Weighted average remaining contractual life (Year)	7 years 102 days
Stock options exercisable, Weighted average exercise price (in dollars per share) | $ / shares	$ 0.17
Stock options exercisable, Aggregate intrinsic value | $	$ 954
Stock options expected to vest, Options (in shares)	1,138,500
Stock options expected to vest, Weighted average remaining contractual life (Year)	8 years 164 days
Stock options expected to vest, Weighted average exercise price (in dollars per share) | $ / shares	$ 0.19
Stock options expected to vest, Aggregate intrinsic value | $	$ 745
Options exercisable and expected to vest, Options (in shares)	2,572,000