Note 13 - Income Taxes - Reconciliation of Effective Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Statutory U.S. federal income tax rate	21.00%	21.00%
State and local income taxes, net of federal income tax benefit	(8.00%)	2.00%
Permanent differences	(2.60%)	(0.40%)
Change in valuation allowance	(15.90%)	(23.10%)
Other	2.70%	(0.50%)
Effective income tax rate	(2.80%)	(1.00%)