Note 9 - Income Taxes Income Tax (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Operating Loss Carryforwards [Line Items]
Deferred Tax Liabilities, Net	$ 126.9	$ 71.1
US Treasury Securities
Operating Loss Carryforwards [Line Items]
Debt Securities	191.9	134.8
Internal Revenue Service (IRS)
Operating Loss Carryforwards [Line Items]
Income Taxes Payable, Federal, Current	32.6	$ 39.1
State and Local NOL Carryforwards
Operating Loss Carryforwards [Line Items]
Valuation Allowance, Amount	$ 68.5