Note 5 - Derivative and Other Hedging Instruments - Schedule of Derivative Positions (Details) - Short [Member] - USD ($)	Mar. 31, 2024	Dec. 31, 2023
Five Year Treasury Note Futures [Member]
Average contract notional amount	$ 421,500,000	$ 421,500,000
Weighted average entry rate	4.26%	4.36%
Average receive rate	4.42%	4.04%
Open Equity	$ (1,099,000)	$ (9,936,000)
Ten Year Ultra Futures [Member]
Average contract notional amount	$ 320,000	$ 320,000,000
Weighted average entry rate	4.29%	4.38%
Average receive rate	4.64%	4.39%
Open Equity	$ (2,475)	$ (11,393,000)
Three Month SOFR Futures, Ending June 2024 [Member}
Average contract notional amount	$ 25,000,000	$ 25,000,000
Weighted average entry rate	4.27%	5.08%
Average receive rate	4.87%	4.99%
Open Equity	$ 149,000	$ (24,000)
Three Month SOFR Futures Ending September 2024 [Member]
Average contract notional amount	$ 25,000,000	$ 25,000,000
Weighted average entry rate	3.90%	4.67%
Average receive rate	4.57%	4.52%
Open Equity	$ 168,000	$ (39,000)
Three Month SOFR Futures Ending in December 2024 [Member]
Average contract notional amount	$ 25,000,000	$ 25,000,000
Weighted average entry rate	3.58%	4.27%
Average receive rate	4.30%	4.10%
Open Equity	$ 179,000	$ (44,000)
Three Month SOFR Futures Ending in March 2025 [Member]
Average contract notional amount	$ 25,000,000	$ 25,000,000
Weighted average entry rate	3.37%	3.90%
Average receive rate	4.07%	3.73%
Open Equity	$ 175,000	$ (43,000)
Three Month SOFR Futures Ending in June 2025 [Member]
Average contract notional amount	$ 25,000,000	$ 25,000,000
Weighted average entry rate	3.25%	3.58%
Average receive rate	3.88%	3.42%
Open Equity	$ 158,000	$ (41,000)
Three Month SOFR Futures Ending in September 2025 [Member]
Average contract notional amount	$ 25,000,000	$ 25,000,000
Weighted average entry rate	3.21%	3.37%
Average receive rate	3.76%	3.21%
Open Equity	$ 138,000	$ (39,000)
Three Month SOFR Futures Ending in December 2025 [Member]
Average contract notional amount		$ 25,000,000
Weighted average entry rate		3.25%
Average receive rate		3.10%
Open Equity		$ (37,000)
Three Month SOFR Futures Ending in March 2026 [Member]
Average contract notional amount		$ 25,000,000
Weighted average entry rate		3.21%
Average receive rate		3.07%
Open Equity		$ (35,000)