Note 6 - Investments Trading Securities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016
Debt and Equity Securities, FV-NI [Line Items]
Other Than Temporary Impairment Losses, Investments, Credit Losses, Portion Recognized in AOCI	$ 0	$ 0		$ 0
Debt Securities, Trading, and Equity Securities, FV-NI	469,071	606,434	[1]
State and municipal obligations
Debt and Equity Securities, FV-NI [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI	168,359	214,841
Corporate bonds and notes
Debt and Equity Securities, FV-NI [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI	228,151	307,271
RMBS
Debt and Equity Securities, FV-NI [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI	21,083	29,520
CMBS
Debt and Equity Securities, FV-NI [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI	51,478	50,561
Foreign government and agency securities
Debt and Equity Securities, FV-NI [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI	$ 0	$ 4,241

[1] At December 31, 2017, includes a de minimis amount of loaned securities under securities lending agreements that are classified as other assets in our consolidated balance sheets, as further described below.