Note 6 - Income Taxes (Details Textual) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	21.00%
Deferred Tax Assets, Valuation Allowance, Total	$ 0.1
Deferred Tax Liabilities, Net, Total	71.2
Deferred Tax Assets Related to State Net Operating Loss Carry Forwards [Member]
Deferred Tax Assets, Valuation Allowance, Total	$ 0.4