Note 9 - Income Taxes Income Tax (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Operating Loss Carryforwards [Line Items]
Deferred Tax Liabilities, Net	$ 90.5	$ 71.1
US Treasury Securities
Operating Loss Carryforwards [Line Items]
Debt Securities	134.8	134.8
Internal Revenue Service (IRS)
Operating Loss Carryforwards [Line Items]
Income Taxes Payable, Federal, Current	42.4	$ 39.1
State and Local NOL Carryforwards
Operating Loss Carryforwards [Line Items]
Valuation Allowance, Amount	$ 67.4