Note 8 - Stock-based Compensation - Stock Option Activity (Details)	9 Months Ended
	Sep. 30, 2020 USD ($) $ / shares shares
Outstanding, number of options (in shares) | shares	747,500
Outstanding, option, weighted average exercise price (in dollars per share) | $ / shares	$ 3.33
Granted, options (in shares) | shares
Grantedg, option, weighted average exercise price (in dollars per share) | $ / shares
Exercised, options (in shares) | shares
Exercisedg, option, weighted average exercise price (in dollars per share) | $ / shares
Expired or forfeited, options (in shares) | shares	(80,000)
Expired or forfeitedg, option, weighted average exercise price (in dollars per share) | $ / shares	$ 5.79
Outstanding, number of options (in shares) | shares	667,500
Outstandingg, option, weighted average exercise price (in dollars per share) | $ / shares	$ 3.04
Outstanding, weighted average remaining contractual term (Year)	4 years 175 days
Outstanding, aggregate intrinsic value | $
Exercisable, options (in shares) | shares	667,500
Exercisableg, option, weighted average exercise price (in dollars per share) | $ / shares	$ 3.04
Exercisable, weighted average remaining contractual term (Year)	4 years 175 days
Exercisable, aggregate intrinsic value | $