Note 5 - Investments Investments Trading Securities (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities	$ 1,209,089	$ 1,279,137
Marketable Securities, Unrealized Gain (Loss)	32,300	(25,200)
US government and agency securities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities	98,869	129,913
State and municipal obligations
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities	311,650	303,946
Corporate bonds and notes
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities	582,035	580,993
RMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities	69,304	72,192
CMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities	124,851	137,678
Other ABS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities	8,911	16,131
Foreign government securities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities	13,469	13,268
Equity securities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities	$ 0	$ 25,016