Note 5 - Derivative and Other Hedging Instruments - Schedule of Derivative Positions (Details) - Short [Member] - USD ($)		Dec. 31, 2024	Dec. 31, 2023
Five Year Treasury Note Futures [Member]
Average contract notional amount	[1]	$ 312,500,000	$ 421,500,000
Weighted average entry rate	[1]	4.22%	4.36%
Average receive rate	[1]	4.37%	4.04%
Open Equity	[1],[2]	$ 1,890,000	$ (9,936,000)
Ten Year T-Note Futures [Member]
Average contract notional amount		$ 93,500,000
Weighted average entry rate		4.30%
Average receive rate		4.49%
Open Equity		$ 1,119,000
Ten Year Ultra Futures [Member]
Average contract notional amount		$ 32,500,000	$ 320,000
Weighted average entry rate		4.25%	4.38%
Average receive rate		4.58%	4.39%
Open Equity		$ 914,000	$ (11,393,000)
Three Month SOFR Futures, Ending June 2024 [Member}
Average contract notional amount			$ 25,000,000
Weighted average entry rate			5.08%
Average receive rate			4.99%
Open Equity	[2]		$ (24,000)
Three Month SOFR Futures Ending September 2024 [Member]
Average contract notional amount			$ 25,000,000
Weighted average entry rate			4.67%
Average receive rate			4.52%
Open Equity	[2]		$ (39,000)
Three Month SOFR Futures Ending in December 2024 [Member]
Average contract notional amount			$ 25,000,000
Weighted average entry rate			4.27%
Average receive rate			4.10%
Open Equity	[2]		$ (44,000)
Three Month SOFR Futures Ending in March 2025 [Member]
Average contract notional amount			$ 25,000,000
Weighted average entry rate			3.90%
Average receive rate			3.73%
Open Equity	[2]		$ (43,000)
Three Month SOFR Futures Ending in June 2025 [Member]
Average contract notional amount			$ 25,000,000
Weighted average entry rate			3.58%
Average receive rate			3.42%
Open Equity	[2]		$ (41,000)
Three Month SOFR Futures Ending in September 2025 [Member]
Average contract notional amount			$ 25,000,000
Weighted average entry rate			3.37%
Average receive rate			3.21%
Open Equity	[2]		$ (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	[2]		$ (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	[2]		$ (35,000)

[1] 10-Year T-Note futures contracts were valued at a price of $114.28 at September 30, 2024 and $112.89 at December 31, 2023. The contract values of the short positions were $14.3 million and $361.2 million at September 30, 2024 and December 31, 2023, respectively. 5-Year T-Note futures contracts were valued at a price of $108.77 at December 31, 2023. The contract value of the short position was $458.5 million at December 31, 2023.

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