Note 3 - Income Taxes (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	21.00%
Alternative Minimum Tax			$ 12,000
Tax Credit Carryforward, Amount	$ 2,700,000	$ 2,700,000
Unrecognized Tax Benefits, Period Increase (Decrease), Total	527,000
Domestic Tax Authority [Member] | Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards, Total	30,700,000	30,400,000
State and Local Jurisdiction [Member]
Operating Loss Carryforwards, Total	$ 19,000,000	$ 19,700,000