Note 5 - Derivative and Other Hedging Instruments - Schedule of Derivative Positions (Details) - Short [Member] - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Five Year Treasury Note Futures [Member]
Average contract notional amount	$ 421,500	$ 750,500
Weighted average entry rate	4.36%	4.20%
Average receive rate	4.04%	4.22%
Open Equity	$ (9,936)	$ (100)
Ten Year Ultra Futures [Member]
Average contract notional amount	$ 320,000	$ 174,500
Weighted average entry rate	4.38%	3.66%	[1]
Average receive rate	4.39%	3.79%
Open Equity	$ (11,393)	$ 965	[2]
Three Month SOFR Futures, Ending June 2024 [Member}
Average contract notional amount	$ 25,000
Weighted average entry rate	5.08%
Average receive rate	4.99%
Open Equity	$ (24)
Three Month SOFR Futures Ending September 2024 [Member]
Average contract notional amount	$ 25,000
Weighted average entry rate	4.67%
Average receive rate	4.52%
Open Equity	$ (39)
Three Month SOFR Futures Ending in December 2024 [Member]
Average contract notional amount	$ 25,000
Weighted average entry rate	4.27%
Average receive rate	4.10%
Open Equity	$ (44)
Three Month SOFR Futures Ending in March 2025 [Member]
Average contract notional amount	$ 25,000
Weighted average entry rate	3.90%
Average receive rate	3.73%
Open Equity	$ (43)
Three Month SOFR Futures Ending in June 2025 [Member]
Average contract notional amount	$ 25,000
Weighted average entry rate	3.58%
Average receive rate	3.42%
Open Equity	$ (41)
Three Month SOFR Futures Ending in September 2025 [Member]
Average contract notional amount	$ 25,000
Weighted average entry rate	3.37%
Average receive rate	3.21%
Open Equity	$ (39)
Three Month SOFR Futures Ending in December 2025 [Member]
Average contract notional amount	$ 25,000
Weighted average entry rate	3.25%
Average receive rate	3.10%
Open Equity	$ (37)
Three Month SOFR Futures Ending in March 2026 [Member]
Average contract notional amount	$ 25,000
Weighted average entry rate	3.21%
Average receive rate	3.07%
Open Equity	$ (35)

[1] 5-Year T-Note futures contracts were valued at a price of $105.4 at September 30, 2023 and $107.9 at December 31, 2022. The contract values of the short positions were $496.7 million and $810.0 million at September 30, 2023 and December 31, 2022, respectively. 10-Year T-Note futures contracts were valued at a price of $108.1 at September 30, 2023. The contract values of the short positions were $426.8 million at September 30, 2023.

[2] Open equity represents the cumulative gains (losses) recorded on open futures positions from inception.