Note 8 - Common Stock - Activity of Stock Option Plan (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) $ / shares shares
Outstanding, options (in shares) | shares	7,024,275
Outstanding, weighted average exercise price, options (in dollars per share) | $ / shares	$ 0.29
Granted, options (in shares) | shares	7,930,000
Granted, weighted average exercise price, options (in dollars per share) | $ / shares	$ 0.03
Forfeited or expired, options (in shares) | shares	(235,000)
Forfeited or expired, weighted average exercise price, options (in dollars per share) | $ / shares	$ 2.96
Outstanding, options (in shares) | shares	14,719,275
Outstanding, weighted average exercise price, options (in dollars per share) | $ / shares	$ 0.11
Outstanding, weighted average exercise price, options (Year)	9 years
Outstanding, weighted average exercise price, options | $	$ 0
Exercisable, options (in shares) | shares	6,795,277
Exercisable at March 31, 2016, weighted average exercise price, options (in dollars per share) | $ / shares	$ 0.19
Exercisable at March 31, 2016, weighted average exercise price, options (Year)	8 years 109 days
Exercisable at March 31, 2016, weighted average exercise price, options | $	$ 0