Note 4 - Income Taxes - Effective Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Tax at federal statutory rate	21.00%	21.00%	21.00%
State taxes, net of federal	3.60%	7.40%	39.20%
Permanent items	3.70%	30.60%	284.40%
Other	(0.70%)	(0.20%)	5.60%
State rate change	0.50%	(0.50%)	0.20%
Valuation allowance	(28.60%)	(58.80%)	(352.50%)
Effective tax rate	(0.50%)	(0.50%)	(2.10%)