Note 13 - Stock Based Compensation - Stock Option Activity (Details)	9 Months Ended
	Sep. 30, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($)
Outstanding, shares (in shares) | shares	4,308,383
Outstanding, weighted average exercise price per share (in dollars per share) | $ / shares	$ 3.44
Outstanding, aggregate intrinsic value | $	$ 5,629,600	$ 651,000
Granted, shares (in shares) | shares	3,140,000
Granted, weighted average exercise price per share (in dollars per share) | $ / shares	$ 1.79
Granted, aggregate intrinsic value | $	$ 449,600
Exercised, shares (in shares) | shares	(225,000)
Exercised, weighted average exercise price per share (in dollars per share) | $ / shares	$ 2.40
Exercised, aggregate intrinsic value | $	$ 297,250
Forfeited, shares (in shares) | shares	(143,552)
Forfeited, weighted average exercise price per share (in dollars per share) | $ / shares	$ 1.87
Forfeited, aggregate intrinsic value | $	$ 272,000
Expired, shares (in shares) | shares
Expired, weighted average exercise price per share (in dollars per share) | $ / shares
Outstanding, shares (in shares) | shares	7,079,831
Outstanding, weighted average exercise price per share (in dollars per share) | $ / shares	$ 2.77
Outstanding, weighted average contractual life remaining in years (Year)	8 years 310 days
Exercisable, shares (in shares) | shares	4,332,821
Exercisable, Weighted average exercise price per share (in dollars per share) | $ / shares	$ 3.34
Exercisable, weighted average contractual life remaining in years (Year)	8 years 153 days
Exercisable, aggregate intrinsic value | $	$ 3,616,727
Vested and expected to vest, shares (in shares) | shares	7,079,831
Vested and expected to vest, Weighted average exercise price per share (in dollars per share) | $ / shares	$ 2.77
Vested and expected to vest, weighted average contractual life remaining in years (Year)	8 years 310 days
Vested and expected to vest, aggregate intrinsic value | $	$ 5,629,600