Note 10 - Stock Based Compensation - Summary of Nonvested Stock Option Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Nonvested, number of shares (in shares)	242,000	318,000
Nonvested, weighted average grant date fair value (in dollars per share)	$ 3.06	$ 3.16
Granted, shares (in shares)	35,000	45,000	35,000
Granted, weighted average grant date fair value (in dollars per share)	$ 2.63	$ 2.48
Vested, number of shares (in shares)	(113,500)	(103,000)
Vested, weighted average grant date fair value (in dollars per share)	$ 2.66	$ 3.26
Forfeited, number of shares (in shares)	(17,000)	(18,000)
Forfeited, weighted average grant date fair value (in dollars per share)	$ 2.52	$ 2.23
Nonvested, number of shares (in shares)	146,500	242,000	318,000
Nonvested, weighted average grant date fair value (in dollars per share)	$ 2.90	$ 3.06	$ 3.16