Note 6 - Income Taxes - Effective Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Tax at federal statutory rate	21.00%	21.00%	21.00%
State taxes, net of federal	39.20%	36.60%	(1.20%)
Permanent items	284.40%	312.20%	(2.40%)
Other	5.60%	5.60%	(0.10%)
State rate change	0.20%	(24.00%)	15.80%
Valuation allowance	(352.50%)	(362.70%)	(34.50%)
Effective tax rate	(2.10%)	(11.60%)	(1.50%)