Note 8 - Income Taxes (Details Textual) - USD ($)	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 3,300,000	$ 3,300,000
Unrecognized Tax Benefits, Interest on Income Taxes Accrued	150,000	150,000
Unrecognized Tax Benefits, Income Tax Penalties Accrued	$ 0	$ 0
Effective Income Tax Rate Reconciliation, Percent, Total	20.00%
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%
Domestic Tax Authority [Member]
Open Tax Year	2017 2018 2019 2020
State and Local Jurisdiction [Member]
Open Tax Year	2016 2017 2018 2019 2020