Note 12 - Stockholders' Equity - Non-vested Stock Options Activity (Details)	12 Months Ended
	Dec. 31, 2021 $ / shares shares
Outstanding, options (in shares)	889,636
Cancelled/forfeited (in shares)	(535,450)
Cancelled/forfeited, Weighted-Average Grant Date Fair Value (in dollars per share) | $ / shares	$ 5.89
Outstanding, options (in shares)	353,420
Non-vested Stock Options [Member]
Outstanding, options (in shares)	658,800
Outstanding, Weighted-Average Grant Date Fair Value (in dollars per share) | $ / shares	$ 5.25
Vested (in shares)	(61,400)
Vested, Weighted-Average Grant Date Fair Value (in dollars per share) | $ / shares	$ 6.18
Cancelled/forfeited (in shares)	(523,500)
Cancelled/forfeited, Weighted-Average Grant Date Fair Value (in dollars per share) | $ / shares	$ 5.05
Outstanding, options (in shares)	73,900
Outstanding, Weighted-Average Grant Date Fair Value (in dollars per share) | $ / shares	$ 5.94