Note 4 - Derivative and Other Hedging Instruments - Schedule of Derivative Instruments Gain (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
(Losses) gains on derivative and other hedging instruments	$ (41,156)	$ 177,498	$ 177,498
Treasury Note Future [Member] | Short [Member]
(Losses) gains on derivative and other hedging instruments	(4,038)		79,691
Interest Rate Swap [Member]
(Losses) gains on derivative and other hedging instruments	(26,144)		66,170
Payer Swaptions [Member] | Short [Member]
(Losses) gains on derivative and other hedging instruments	6,585		(10,908)
Payer Swaptions [Member] | Long [Member]
(Losses) gains on derivative and other hedging instruments	(12,109)		40,975
Interest Rate Cap [Member]
(Losses) gains on derivative and other hedging instruments	(645)		(996)
Interest Rate Floor [Member]
(Losses) gains on derivative and other hedging instruments	1,185		0
TBA Contracts [Member] | Short [Member]
(Losses) gains on derivative and other hedging instruments	(5,990)		2,539
TBA Contracts [Member] | Long [Member]
(Losses) gains on derivative and other hedging instruments	$ 0		$ 27