Note 2 - Mortgage-backed Securities and U.S. Treasury Securities, at Fair Value (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Notional Balance, Interest Only Securities Portfolio, Amount	$ 72,900	$ 85,800
Notional Balance, Inverse Interest Only Securities Portfolio, Amount	17,700	22,000
Investment Sold at Carrying Value	$ (1,386,412)	(458,874)	$ (820,275)
Collateralized Mortgage-Backed Securities [Member]
Investment Sold at Carrying Value		$ 221,700