Note 4 - Derivative and Other Hedging Instruments - Schedule of Derivative Instruments Gain (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Gains on derivative and other hedging instruments	$ 93,367	$ 103,367	$ 52,211	$ 280,865
Treasury Note Future [Member] | Short [Member]
Gains on derivative and other hedging instruments	28,040	42,931	24,002	122,622
Interest Rate Swap [Member]
Gains on derivative and other hedging instruments	49,084	39,570	22,940	105,740
Payer Swaptions [Member] | Short [Member]
Gains on derivative and other hedging instruments	(1,754)	(34,036)	4,831	(44,944)
Payer Swaptions [Member] | Long [Member]
Gains on derivative and other hedging instruments	3,107	50,339	(9,002)	91,314
Interest Rate Cap [Member]
Gains on derivative and other hedging instruments	(263)	2,483	(908)	1,487
Interest Rate Floor [Member] | Short [Member]
Gains on derivative and other hedging instruments	(1,216)	0	(1,216)	0
Interest Rate Floor [Member] | Long [Member]
Gains on derivative and other hedging instruments	1,344		2,529	0
TBA Contracts [Member] | Short [Member]
Gains on derivative and other hedging instruments	15,599	1,013	9,609	3,552
TBA Contracts [Member] | Long [Member]
Gains on derivative and other hedging instruments	$ (574)	$ 1,067	$ (574)	$ 1,094