Note 13 - Income Taxes - Components of Company's Deferred Tax Assets and Liabilities for Federal and State Income Taxes (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Net operating loss carryforwards	$ 27,312,000	$ 26,758,000
Income tax credit carryforwards	2,852,000	2,757,000
Stock compensation	369,000	384,000
Lease obligation	160,000	185,000
Deferred revenue	340,000	419,000
Other	528,000	943,000
Total deferred tax assets	31,561,000	31,446,000
Depreciation and amortization	(352,000)	(408,000)
Lease asset	(153,000)	(180,000)
Total deferred tax liabilities	(505,000)	(588,000)
Valuation allowance	(31,056,000)	(30,858,000)
Net deferred taxes