Note 5 - Investments Investments Trading Securities (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Schedule of Trading Securities and Other Trading Assets [Line Items]
Unrealized Gain (Loss) on Trading Securities Held	$ 8,000	$ 16,800
Trading Securities	708,788	879,862
US government and agency securities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities	28,336	33,042
State and municipal obligations
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities	216,838	259,573
Corporate bonds and notes
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities	360,906	453,617
RMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities	34,114	38,214
CMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities	64,267	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	$ 4,327	$ 8,213