Note 5 - Investments Investments Trading Securities (Details) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2017		Dec. 31, 2016
Schedule of Trading Securities and Other Trading Assets [Line Items]
Unrealized Gain (Loss) on Trading Securities Held	$ 10,000		$ 16,800
Trading Securities	636,276	[1]	879,862
US government and agency securities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities	0		33,042
State and municipal obligations
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities	214,599		259,573
Corporate bonds and notes
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities	327,306		453,617
RMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities	31,742		38,214
CMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities	58,337		78,984
Other ABS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities	0		8,219
Foreign government securities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities	$ 4,292		$ 8,213

[1] Includes loaned securities under securities lending agreements that are classified as other assets in our condensed consolidated balance sheets, as further described below.