Note 10 - Income Taxes - Income Tax (Details) - USD ($) $ in Thousands	1 Months Ended
	Jul. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Operating Loss Carryforwards [Line Items]
Deferred Tax Liabilities, Net		$ 166,100	$ 71,100
2015 and 2017 Tax Years [Member]
Operating Loss Carryforwards [Line Items]
Income Tax Credits and Adjustments	$ 0
US Treasury Securities
Operating Loss Carryforwards [Line Items]
Debt Securities		191,900	134,800
Internal Revenue Service (IRS)
Operating Loss Carryforwards [Line Items]
Income Taxes Payable, Federal, Current		26,600	$ 39,100
State and Local NOL Carryforwards
Operating Loss Carryforwards [Line Items]
Valuation Allowance, Amount		$ 67,900