Note 5 - Derivative and Other Hedging Instruments - Schedule of Derivative Instruments Gain (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Gains on derivative and other hedging instruments	$ 142,042	$ 183,931	$ 194,253	$ 464,796
Treasury Note Future [Member] | Short [Member]
Gains on derivative and other hedging instruments	42,640	84,543	66,642	207,165
Interest Rate Swap [Member]
Gains on derivative and other hedging instruments	78,317	65,247	101,257	170,987
Payer Swaptions [Member] | Short [Member]
Gains on derivative and other hedging instruments	(718)	(35,239)	4,113	(80,183)
Payer Swaptions [Member] | Long [Member]
Gains on derivative and other hedging instruments	1,613	59,131	(7,389)	150,445
Interest Rate Cap [Member]
Gains on derivative and other hedging instruments	493	(499)	(415)	988
Interest Rate Floor [Member] | Short [Member]
Gains on derivative and other hedging instruments	73	0	(1,143)	0
Interest Rate Floor [Member] | Long [Member]
Gains on derivative and other hedging instruments	137		2,666
TBA Contracts [Member] | Short [Member]
Gains on derivative and other hedging instruments	21,511	10,642	31,120	14,194
TBA Contracts [Member] | Long [Member]
Gains on derivative and other hedging instruments	$ (2,024)	$ 106	$ (2,598)	$ 1,200