Note 2 - Mortgage-backed Securities and U.S. Treasury Securities, at Fair Value - Gain (Loss) on Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Sales and maturities	$ 454,272	$ 797,633	$ 2,759,919
Carrying value of RMBS sold	(458,874)	(820,275)	(2,893,614)
Realized losses on mortgage-backed securities	(4,602)	(22,642)	(133,695)
Gross gain on sales of RMBS	510	0	2,705
Gross loss on sales of RMBS	$ (5,112)	$ (22,642)	$ (136,400)