Note 2 - Mortgage-backed Securities and U.S. Treasury Securities, at Fair Value - Gain (Loss) on Investments (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Sales and maturities	[1]			$ 733,904	$ 288,242
Carrying value of RMBS sold				(743,192)	(287,732)
Realized (losses) gains on mortgage-backed securities		$ 0	$ 510	(9,288)	510
Gross gain on sales of RMBS				0	510
Gross loss on sales of RMBS				$ (9,288)	$ 0

[1] During the nine months ended September 30, 2024, the Company resecuritized RMBS with a fair value of $221.7 million by transferring the RMBS into a larger RMBS that is backed by the transferred RMBS. The Company retained the entire larger RMBS. No gain or loss was recorded on this resecuritization.