Note 10 - Stockholders' Equity - Outstanding and Exercisable Options (Details)	12 Months Ended
	Dec. 31, 2021 USD ($) $ / shares shares
Exercise price range, lower limit (in dollars per share)	$ 12.01
Exercise price range, upper limit (in dollars per share)	$ 15.00
Number of options outstanding (in shares) | shares	100,000
Number of options outstanding, weighted average remaining contractual term (Year)	7 months 6 days
Number of options outstanding, weighted average exercise price (in dollars per share)	$ 15.00
Number of options outstanding, intrinsic value | $	$ 0
Number of options exercisable (in shares) | shares	100,000
Number of options exercisable, weighted average exercise price (in dollars per share)	$ 15.00
Number of options exercisable, intrinsic value | $	$ 0
Exercise Price Range 1 [Member]
Exercise price range, lower limit (in dollars per share)	$ 4.00
Exercise price range, upper limit (in dollars per share)	$ 7.00
Number of options outstanding (in shares) | shares	378,500
Number of options outstanding, weighted average remaining contractual term (Year)	9 years 3 months 18 days
Number of options outstanding, weighted average exercise price (in dollars per share)	$ 4.23
Number of options outstanding, intrinsic value | $	$ 21,000
Number of options exercisable (in shares) | shares	45,000
Number of options exercisable, weighted average exercise price (in dollars per share)	$ 5.00
Number of options exercisable, intrinsic value | $	$ 0
Exercise Price Range 2 [Member]
Exercise price range, lower limit (in dollars per share)	$ 7.01
Exercise price range, upper limit (in dollars per share)	$ 10.00
Number of options outstanding (in shares) | shares	20,000
Number of options outstanding, weighted average remaining contractual term (Year)	6 years 3 months 18 days
Number of options outstanding, weighted average exercise price (in dollars per share)	$ 8.07
Number of options outstanding, intrinsic value | $	$ 0
Number of options exercisable (in shares) | shares	20,000
Number of options exercisable, weighted average exercise price (in dollars per share)	$ 8.07
Number of options exercisable, intrinsic value | $	$ 0
Exercise Price Range 3 [Member]
Exercise price range, lower limit (in dollars per share)	$ 10.01
Exercise price range, upper limit (in dollars per share)	$ 12.00
Number of options outstanding (in shares) | shares	120,000
Number of options outstanding, weighted average remaining contractual term (Year)	3 years 7 months 6 days
Number of options outstanding, weighted average exercise price (in dollars per share)	$ 10.52
Number of options outstanding, intrinsic value | $	$ 0
Number of options exercisable (in shares) | shares	100,000
Number of options exercisable, weighted average exercise price (in dollars per share)	$ 10.56
Number of options exercisable, intrinsic value | $	$ 0