Note 4 - Derivative and Other Hedging Instruments - Schedule of Derivative Positions (Details) - Short [Member] - USD ($) $ in Thousands		Jun. 30, 2023	Dec. 31, 2022
Five Year Treasury Note Futures [Member]
Average contract notional amount		$ 471,500	$ 750,500
Weighted average entry rate		3.69%	4.20%
Average receive rate		4.40%	4.22%
Open Equity		$ 9,795	$ (100)
Ten Year T-Note Futures [Member]
Average contract notional amount		$ 285,000
Weighted average entry rate		3.76%
Average receive rate		4.47%
Open Equity		$ 3,793
Ten Year Ultra Future [Member]
Average contract notional amount		$ 244,200	$ 174,500
Weighted average entry rate	[1]	3.71%	3.66%
Average receive rate		3.77%	3.79%
Open Equity	[2]	$ 2,182	$ 965

[1] 5-Year T-Note futures contracts were valued at a price of $109.5 at March 31, 2023 and $107.9 at December 31, 2022. The contract values of the short positions were $1,014.6 million and $810.0 million at March 31, 2023 and December 31, 2022, respectively. 10-Year Ultra futures contracts were valued at a price of $121.1 at March 31, 2023 and $118.3 at December 31, 2022. The contract value of the short position was $65.7 million and $206.4 million at March 31, 2023 and December 31, 2022, respectively

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