Note 2 - Mortgage-backed Securities and U.S. Treasury Securities, at Fair Value (Details Textual) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Notional Balance, Interest Only Securities Portfolio, Amount	$ 78,400		$ 85,800
Notional Balance, Inverse Interest Only Securities Portfolio, Amount	18,400		$ 22,000
Investment Sold at Carrying Value	$ 743,192	$ 287,732
Collateralized Mortgage-Backed Securities [Member]
Investment Sold at Carrying Value		$ 221,700