Note 5 - Derivative and Other Hedging Instruments - Schedule of Derivative Positions (Details) - Short [Member] - USD ($) $ in Thousands		Sep. 30, 2023	Dec. 31, 2022
Five Year Treasury Note Futures [Member]
Average contract notional amount		$ 471,500	$ 750,500
Weighted average entry rate		4.33%	4.20%
Average receive rate		4.78%	4.22%
Open Equity		$ 5,414	$ (100)
Ten Year T-Note Futures [Member]
Average contract notional amount		$ 395,000
Weighted average entry rate		4.24%
Average receive rate		4.97%
Open Equity		$ 9,069
Ten Year Ultra Future [Member]
Average contract notional amount			$ 174,500
Weighted average entry rate	[1]		3.66%
Average receive rate			3.79%
Open Equity	[2]		$ 965

[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.