Note 8 - Derivatives Instruments and Hedging Activities (Details) - Derivative Instruments Not Designated as Hedges (USD $)	9 Months Ended
	Sep. 30, 2014 TBA Securities [Member]	Sep. 30, 2013 TBA Securities [Member]	Sep. 30, 2014 US Treasury Futures [Member]	Sep. 30, 2013 US Treasury Futures [Member]	Sep. 30, 2014 Interest Rate Swap [Member]	Sep. 30, 2013 Interest Rate Swap [Member]	Sep. 30, 2014 Eurodollar Future [Member]	Sep. 30, 2013 Eurodollar Future [Member]	Sep. 30, 2014 US Treasury Futures Options [Member]	Sep. 30, 2013 US Treasury Futures Options [Member]	Sep. 30, 2014 Swaption [Member]	Sep. 30, 2013 Swaption [Member]	Dec. 31, 2012 Swaption [Member]
Note 8 - Derivatives Instruments and Hedging Activities (Details) - Derivative Instruments Not Designated as Hedges [Line Items]
Beginning balance	$ 188,000,000	$ 234,000,000	$ (11,900,000)	$ (172,100,000)	$ (242,700,000)	$ (13,000,000)	$ (3,360,000,000)	$ (2,852,000,000)	$ 40,000,000	$ 70,000,000	$ 100,000,000	$ 100,000,000	$ 100,000,000
Additions	1,812,000,000	2,030,000,000	96,700,000	735,100,000	712,900,000	263,700,000	2,649,000,000	2,781,000,000		250,000,000
Settlement, expiration or exercise	(1,792,000,000)	(2,079,000,000)	(86,000,000)	(647,400,000)	(702,800,000)	(413,800,000)	(2,067,000,000)	(2,800,000,000)	(40,000,000)	(310,000,000)	(70,000,000)
Ending balance	$ 208,000,000	$ 185,000,000	$ (1,200,000)	$ (84,400,000)	$ (232,600,000)	$ (163,100)	$ (2,778,000,000)	$ (2,871,000,000)		$ 10,000,000	$ 30,000,000	$ 100,000,000	$ 100,000,000