Note 5 - Investments Trading Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI	$ 493,956	$ 606,434	[1]
State and municipal obligations
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI	185,494	214,841
Corporate bonds and notes
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI	235,422	307,271
RMBS
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI	22,069	29,520
CMBS
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI	50,971	50,561
Foreign government and agency securities
Debt Securities, Available-for-sale [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.