Note 2 - Mortgage-backed Securities and U.S. Treasury Securities, at Fair Value (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Notional Balance, Interest Only Securities Portfolio, Amount	$ 85,800	$ 98,600
Notional Balance, Inverse Interest Only Securities Portfolio, Amount	22,000	26,800
Investment Sold at Carrying Value	(458,874)	$ (820,275)	$ (2,893,614)
Collateralized Mortgage-Backed Securities [Member]
Investment Sold at Carrying Value	$ (221,700)