Note 4 - Derivative and Other Hedging Instruments - Schedule of Derivative Instruments Gain (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Gains (losses) on derivative instruments	$ 455,736	$ 26,877	$ (79,092)
Five Year Treasury Note Futures [Member] | Short [Member]
Gains (losses) on derivative instruments	207,511	(846)	(4,707)
Eurodollar Future Margin [Member] | Short [Member]
Gains (losses) on derivative instruments	0	(10)	(8,337)
Interest Rate Swap [Member]
Gains (losses) on derivative instruments	170,297	23,613	(66,212)
Payer Swaptions [Member] | Short [Member]
Gains (losses) on derivative instruments	(81,050)	9,062	(3,070)
Payer Swaptions [Member] | Long [Member]
Gains (losses) on derivative instruments	152,365	(2,580)	98
Interest Rate Cap [Member]
Gains (losses) on derivative instruments	919	0	0
Interest Rate Floor [Member]
Gains (losses) on derivative instruments	0	2,765	0
TBA Contracts [Member] | Short [Member]
Gains (losses) on derivative instruments	4,494	3,432	(6,719)
TBA Contracts [Member] | Long [Member]
Gains (losses) on derivative instruments	1,200	(8,559)	9,950
US Treasury Securities [Member] | Short [Member]
Gains (losses) on derivative instruments	$ 0	$ 0	$ (95)